Add support for defining package capabilities

This check was broken: it tried to construct a http URL
by changing the updateBaseUrl schema instead of constructing
such a URL based on the configured HTTPPort.

I also don’t think this check is useful:
HTTPS will be used for updates regardless of the check.
Even if an attacker intercepted HTTP traffic and removed the redirect,
that has no bearing on the update, so why bother checking.

One thing the check (implicitly) did is the required fallback
on initial installation when --insecure is specified.
We now solve that by falling back from HTTPS to HTTP explicitly
(only when --insecure is specified, of course).

related to https://github.com/gokrazy/tools/pull/94

.github/workflows/push.yml

@@ -35,6 +35,10 @@ jobs:
       run: |
         go install -mod=mod ./cmd/...
 
+    - name: install qemu
+      if: matrix.os == 'ubuntu-latest'
+      run: sudo apt update && sudo apt-get install qemu-system-x86
+
     - name: Run tests
       if: matrix.os == 'ubuntu-latest'
       # TestRelativeParentDir verifies breakglass.authorized_keys

flake.lock

@@ -0,0 +1,78 @@
+{
+  "nodes": {
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1731533236,
+        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1763049705,
+        "narHash": "sha256-A5LS0AJZ1yDPTa2fHxufZN++n8MCmtgrJDtxFxrH4S8=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "3acb677ea67d4c6218f33de0db0955f116b7588c",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-25.05",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs",
+        "rpi-eeprom-tools": "rpi-eeprom-tools"
+      }
+    },
+    "rpi-eeprom-tools": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1758789610,
+        "narHash": "sha256-1aGazeN4Ou5GRMCRETie4I0E08mlAQFWp6cGURB1NIM=",
+        "owner": "info-beamer",
+        "repo": "rpi-eeprom-tools",
+        "rev": "9ae4d618a0a51789fbde8e9d667881a321cf6721",
+        "type": "github"
+      },
+      "original": {
+        "owner": "info-beamer",
+        "repo": "rpi-eeprom-tools",
+        "type": "github"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,66 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.05";
+    flake-utils.url = "github:numtide/flake-utils";
+    rpi-eeprom-tools = {
+      url = "github:info-beamer/rpi-eeprom-tools";
+      flake = false;
+    };
+  };
+
+  outputs =
+    {
+      self,
+      nixpkgs,
+      flake-utils,
+      rpi-eeprom-tools,
+    }:
+    flake-utils.lib.eachDefaultSystem (
+      system:
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+
+        # Python environment with pycryptodome for pi-eeprom-tools
+        pythonEnv = pkgs.python312.withPackages (
+          ps: with ps; [
+            pycryptodome
+          ]
+        );
+
+        # Helper to create a wrapper for a pi-eeprom-* script
+        mkPiEepromTool =
+          name:
+          pkgs.writeShellApplication {
+            inherit name;
+            runtimeInputs = [
+              pythonEnv
+            ];
+            text = ''
+              exec ${pythonEnv.interpreter} ${rpi-eeprom-tools}/${name} "$@"
+            '';
+          };
+
+        # All the pi-eeprom tools
+        pi-eeprom-extract = mkPiEepromTool "pi-eeprom-extract";
+        pi-eeprom-ls = mkPiEepromTool "pi-eeprom-ls";
+        pi-eeprom-recompress = mkPiEepromTool "pi-eeprom-recompress";
+        pi-eeprom-update = mkPiEepromTool "pi-eeprom-update";
+      in
+      {
+        devShells.default = pkgs.mkShell {
+          buildInputs = with pkgs; [
+            go
+            raspberrypi-eeprom
+            pi-eeprom-extract
+            pi-eeprom-ls
+            pi-eeprom-recompress
+            pi-eeprom-update
+          ];
+
+          shellHook = ''
+            echo "Nix-based gokrazy/tools dev env (go: $(go version))"
+          '';
+        };
+      }
+    );
+}

go.mod

@@ -5,9 +5,10 @@ go 1.24.0
 toolchain go1.24.6
 
 require (
+	github.com/anatol/vmtest v0.0.0-20250627153117-302402d269a6
 	github.com/donovanhide/eventsource v0.0.0-20210830082556-c59027999da0
-	github.com/gokrazy/gokapi v0.0.0-20250222080418-e140e9c461d8
-	github.com/gokrazy/internal v0.0.0-20250526201501-559979153369
+	github.com/gokrazy/gokapi v0.0.0-20251205165548-0927bab199d4
+	github.com/gokrazy/internal v0.0.0-20251208203110-3c1aa9087c82
 	github.com/gokrazy/updater v0.0.0-20250705135802-db129c40879c
 	github.com/google/renameio/v2 v2.0.0
 	github.com/mattn/go-isatty v0.0.20

go.sum

@@ -1,12 +1,16 @@
+github.com/anatol/vmtest v0.0.0-20250627153117-302402d269a6 h1:zdaWj/ncXyzpPH3YqACvJXMrJxkkILrnWbjHojHBctc=
+github.com/anatol/vmtest v0.0.0-20250627153117-302402d269a6/go.mod h1:m5pN88x7ZnEDGXZldwg7RCX+EikR9qz/iSI2GzXq++Y=
 github.com/antihax/optional v1.0.0 h1:xK2lYat7ZLaVVcIuj82J8kIro4V6kDe0AUDFboUCwcg=
 github.com/antihax/optional v1.0.0/go.mod h1:uupD/76wgC+ih3iEmQUL+0Ugr19nfwCT1kdvxnR2qWY=
 github.com/cpuguy83/go-md2man/v2 v2.0.6/go.mod h1:oOW0eioCTA6cOiMLiUPZOpcVxMig6NIQQ7OS05n1F4g=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/donovanhide/eventsource v0.0.0-20210830082556-c59027999da0 h1:C7t6eeMaEQVy6e8CarIhscYQlNmw5e3G36y7l7Y21Ao=
 github.com/donovanhide/eventsource v0.0.0-20210830082556-c59027999da0/go.mod h1:56wL82FO0bfMU5RvfXoIwSOP2ggqqxT+tAfNEIyxuHw=
-github.com/gokrazy/gokapi v0.0.0-20250222080418-e140e9c461d8 h1:BvyzTtbpz1GCGD35Z3G/ZR0nK0j3Fh+dRCCso+w3RKE=
-github.com/gokrazy/gokapi v0.0.0-20250222080418-e140e9c461d8/go.mod h1:rVItujrJo0NpYZhFR5dYdzLDqMoMCtjEZkdxoCRDo+o=
-github.com/gokrazy/internal v0.0.0-20250526201501-559979153369 h1:aNni2iPwJbowfHW1SFapKLfY+ZPUIcBfFrJvYPAh3p4=
-github.com/gokrazy/internal v0.0.0-20250526201501-559979153369/go.mod h1:dQY4EMkD4L5ZjYJ0SPtpgYbV7MIUMCxNIXiOfnZ6jP4=
+github.com/gokrazy/gokapi v0.0.0-20251205165548-0927bab199d4 h1:XFo3EqnHUbmAySp7zqms8ee/tU8bM9k+YzT7L4o5CcQ=
+github.com/gokrazy/gokapi v0.0.0-20251205165548-0927bab199d4/go.mod h1:+StofDb/2cMb7vbA2znaNolgp9SadTYeyRIFtdhH1KQ=
+github.com/gokrazy/internal v0.0.0-20251208203110-3c1aa9087c82 h1:4ghNfD9NaZLpFrqQiBF6mPVFeMYXJSky38ubVA4ic2E=
+github.com/gokrazy/internal v0.0.0-20251208203110-3c1aa9087c82/go.mod h1:dQY4EMkD4L5ZjYJ0SPtpgYbV7MIUMCxNIXiOfnZ6jP4=
 github.com/gokrazy/updater v0.0.0-20250705135802-db129c40879c h1:j4/v9FR/cOy6nog5rmXUtauBsOU3mm+rTPn5IENUbmg=
 github.com/gokrazy/updater v0.0.0-20250705135802-db129c40879c/go.mod h1:EtAn+BPibqnAHnYGj3FW5e284xNsiOOMOL2dJiwu7H4=
 github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
@@ -17,11 +21,15 @@ github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2
 github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
 github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
 github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
 github.com/spf13/cobra v1.9.1 h1:CXSaggrXdbHK9CF+8ywj8Amf7PBRmPCOJugH954Nnlo=
 github.com/spf13/cobra v1.9.1/go.mod h1:nDyEzZ8ogv936Cinf6g1RU9MRY64Ir93oCnqb9wxYW0=
 github.com/spf13/pflag v1.0.6 h1:jFzHGLGAlb3ruxLB8MhbI6A8+AQX/2eW4qeyNZXNp2o=
 github.com/spf13/pflag v1.0.6/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
+github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
 golang.org/x/crypto/x509roots/fallback v0.0.0-20250911151450-96dc232fbd79 h1:WZWglxfb13JCTbJyKY1pk0V94spHxJzMAQW29INytRQ=
 golang.org/x/crypto/x509roots/fallback v0.0.0-20250911151450-96dc232fbd79/go.mod h1:MEIPiCnxvQEjA4astfaKItNwEVZA5Ki+3+nyGbJ5N18=
 golang.org/x/mod v0.24.0 h1:ZfthKaKaT4NrhGVZHO1/WDTwGES4De8KtWO0SIbNJMU=
@@ -34,4 +42,5 @@ golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.33.0 h1:q3i8TbbEz+JRD9ywIRlyRAQbM0qF7hu24q3teo2hbuw=
 golang.org/x/sys v0.33.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

gok/gok.go

@@ -17,7 +17,7 @@ type Context struct {
 }
 
 func (c Context) Execute(ctx context.Context) error {
-	root := gok.RootCmd
+	root := gok.RootCmd()
 	if r := c.Stdin; r != nil {
 		root.SetIn(r)
 	}

integration/gokrun/gokrun_test.go

@@ -136,7 +136,7 @@ func TestGokRun(t *testing.T) {
 
 	// Testing the root command because individual cobra commands cannot be
 	// executed directly.
-	root := gok.RootCmd
+	root := gok.RootCmd()
 	root.SetContext(ctx)
 	logOutputFound := make(chan bool)
 	rd, wr := io.Pipe()

integration/gokupdate/gokupdate_test.go

@@ -2,41 +2,54 @@ package gokupdate_test
 
 import (
 	"context"
-	"crypto/sha256"
 	"encoding/json"
-	"fmt"
-	"hash"
-	"hash/crc32"
-	"io"
-	"log"
 	"net/http"
-	"net/http/httptest"
-	"net/url"
 	"os"
 	"path/filepath"
 	"runtime"
-	"strings"
 	"testing"
 	"time"
 
 	"github.com/gokrazy/internal/config"
+	"github.com/gokrazy/internal/tlsflag"
 	"github.com/gokrazy/tools/gok"
 	"github.com/gokrazy/tools/internal/packer"
 )
 
 type gokrazyTestInstance struct {
+	name      string
 	configDir string
 }
 
-func (inst *gokrazyTestInstance) writeConfig(t *testing.T, basename, content string) {
+func (inst *gokrazyTestInstance) configPath() string {
+	return "gokrazy/" + inst.name + "/config.json"
+}
+
+func (inst *gokrazyTestInstance) readConfig(t *testing.T) config.Struct {
+	b, err := os.ReadFile(inst.configPath())
+	if err != nil {
+		t.Fatal(err)
+	}
+	var cfg config.Struct
+	if err := json.Unmarshal(b, &cfg); err != nil {
+		t.Fatal(err)
+	}
+	return cfg
+}
+
+func (inst *gokrazyTestInstance) writeConfig(t *testing.T, cfg config.Struct) {
 	t.Helper()
-	fn := filepath.Join(inst.configDir, basename)
-	if err := os.WriteFile(fn, []byte(content), 0600); err != nil {
+	t.Logf("Writing updated cfg = %+v", cfg)
+	b, err := cfg.FormatForFile()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(inst.configPath(), b, 0644); err != nil {
 		t.Fatal(err)
 	}
 }
 
-func writeGokrazyInstance(t *testing.T) *gokrazyTestInstance {
+func writeGokrazyInstance(t *testing.T, name string) *gokrazyTestInstance {
 	t.Helper()
 
 	// Redirect os.UserConfigDir() to a temporary directory under our
@@ -64,6 +77,7 @@ func writeGokrazyInstance(t *testing.T) *gokrazyTestInstance {
 	}
 
 	return &gokrazyTestInstance{
+		name:      name,
 		configDir: configDir,
 	}
 }
@@ -73,85 +87,17 @@ func TestGokUpdate(t *testing.T) {
 	// gokrazy/tools repository working copy.
 	t.Chdir(t.TempDir())
 
-	_ = writeGokrazyInstance(t)
-
-	// TODO: run the gokrazy instance in a VM instead of providing a fake
-	// implementation of the update protocol.
-	mux := http.NewServeMux()
-	mux.HandleFunc("/update/features", func(w http.ResponseWriter, r *http.Request) {
-		http.Error(w, "not found", http.StatusNotFound)
-	})
-	mux.HandleFunc("/update/", func(w http.ResponseWriter, r *http.Request) {
-		// accept whatever for now.
-		var hash hash.Hash
-		switch r.Header.Get("X-Gokrazy-Update-Hash") {
-		case "crc32":
-			hash = crc32.NewIEEE()
-		default:
-			hash = sha256.New()
-		}
-		if _, err := io.Copy(hash, r.Body); err != nil {
-			http.Error(w, err.Error(), http.StatusInternalServerError)
-			return
-		}
-		fmt.Fprintf(w, "%x", hash.Sum(nil))
-	})
-	mux.HandleFunc("/reboot", func(w http.ResponseWriter, r *http.Request) {
-		// you got it, boss!
-	})
-	mux.HandleFunc("/uploadtemp/", func(w http.ResponseWriter, r *http.Request) {
-		log.Printf("[HTTP] uploadtemp: %s", r.URL.Path)
-	})
-	mux.HandleFunc("/divert", func(w http.ResponseWriter, r *http.Request) {
-		log.Printf("[HTTP] divert: %s to %s",
-			r.FormValue("path"),
-			r.FormValue("diversion"))
-	})
-	mux.HandleFunc("/log", func(w http.ResponseWriter, r *http.Request) {
-		log.Printf("[HTTP] log: %s", r.FormValue("path"))
-		w.Header().Set("Content-type", "text/event-stream")
-		if r.FormValue("stream") == "stdout" {
-			const text = "Hello Sun"
-			line := fmt.Sprintf("data: %s\n", text)
-			if _, err := fmt.Fprintln(w, line); err != nil {
-				return
-			}
-		}
-		if f, ok := w.(http.Flusher); ok {
-			f.Flush()
-		}
-		select {}
-	})
-	fakeBuildTimestamp := "fake-" + time.Now().Format(time.RFC3339)
-	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
-		if strings.Contains(strings.ToLower(r.Header.Get("Accept")), "application/json") {
-			status := struct {
-				BuildTimestamp string `json:"BuildTimestamp"`
-			}{
-				BuildTimestamp: fakeBuildTimestamp,
-			}
-			b, err := json.Marshal(&status)
-			if err != nil {
-				http.Error(w, err.Error(), http.StatusInternalServerError)
-				return
-			}
-			w.Header().Set("Content-Type", "application/json")
-			w.Write(b)
-			return
-		}
-		http.Error(w, "handler not implemented", http.StatusNotImplemented)
-	})
-	srv := httptest.NewServer(mux)
-	u, err := url.Parse(srv.URL)
-	if err != nil {
-		t.Fatal(err)
-	}
-
 	// create a new instance
+	const (
+		instanceName = "hello"
+		hostname     = "localhost"
+	)
+	ti := writeGokrazyInstance(t, instanceName)
+
 	c := gok.Context{
 		Args: []string{
 			"--parent_dir", "gokrazy",
-			"-i", "hello",
+			"-i", instanceName,
 			"new",
 		},
 	}
@@ -160,33 +106,73 @@ func TestGokUpdate(t *testing.T) {
 		t.Fatalf("%v: %v", c.Args, err)
 	}
 
-	// update the instance config to speak to the test server
-	const configPath = "gokrazy/hello/config.json"
-	b, err := os.ReadFile(configPath)
+	// and update the (default) instance config for our test
+	{
+		cfg := ti.readConfig(t)
+
+		// use generic kernel, enable serial console
+		// TODO: use arm64 kernel when running on arm64
+		kernelPackage := "github.com/gokrazy/kernel.amd64"
+		cfg.KernelPackage = &kernelPackage
+		cfg.FirmwarePackage = &kernelPackage
+		cfg.SerialConsole = "ttyS0,115200"
+		cfg.Environment = []string{"GOOS=linux", "GOARCH=amd64"}
+
+		cfg.Hostname = hostname
+		cfg.Update.Hostname = hostname
+		cfg.Update.HTTPPort = "9080"
+		cfg.Update.HTTPSPort = "9443"
+		t.Logf("Updated cfg.Update = %+v", cfg.Update)
+
+		ti.writeConfig(t, cfg)
+	}
+
+	t.Logf("booting gokrazy instance in a VM")
+	qemu := Run(t, nil)
+	defer qemu.Kill()
+	// TODO: kill the test if this qemu process dies for any reason
+	// test by setting an aggressive QemuOptions.Timeout
+
+	// wait for this instance to become healthy
+	//
+	// TODO: include the actual build timestamp once gok overwrite returns it.
+	if err := qemu.ConsoleExpect("gokrazy build timestamp "); err != nil {
+		t.Fatal(err)
+	}
+	t.Logf("gokrazy VM booted up, waiting for network reachability")
+	// poll for reachability over the network
+	for start := time.Now(); time.Since(start) < 10*time.Second; time.Sleep(1 * time.Second) {
+		ctx, cancel := context.WithTimeout(t.Context(), 1*time.Second)
+		defer cancel()
+		req, err := http.NewRequest("GET", "http://localhost:9080", nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		req = req.WithContext(ctx)
+		resp, err := http.DefaultClient.Do(req)
+		if err != nil {
+			t.Logf("VM not yet reachable: %v", err)
+			continue
+		}
+		if resp.StatusCode == http.StatusUnauthorized {
+			t.Logf("gokrazy VM became reachable over the network")
+			break
+		}
+	}
+
+	// TODO: make 'gok update' not change directory?
+	dir, err := os.Getwd()
 	if err != nil {
 		t.Fatal(err)
 	}
-	var cfg config.Struct
-	if err := json.Unmarshal(b, &cfg); err != nil {
-		t.Fatal(err)
-	}
-	cfg.Update.Hostname = "localhost"
-	cfg.Update.HTTPPort = u.Port()
-	t.Logf("Updated cfg.Update = %+v", cfg.Update)
-	b, err = cfg.FormatForFile()
-	if err != nil {
-		t.Fatal(err)
-	}
-	if err := os.WriteFile(configPath, b, 0644); err != nil {
-		t.Fatal(err)
-	}
 
 	// verify overwrite works (i.e. locates extrafiles)
+	fakeBuildTimestamp := "fake-update-1"
 	ctx := context.WithValue(context.Background(), packer.BuildTimestampOverride, fakeBuildTimestamp)
 	c = gok.Context{
 		Args: []string{
 			"--parent_dir", "gokrazy",
-			"-i", "hello",
+			"-i", instanceName,
 			"update",
 		},
 	}
@@ -194,4 +180,83 @@ func TestGokUpdate(t *testing.T) {
 	if err := c.Execute(ctx); err != nil {
 		t.Fatalf("%v: %v", c.Args, err)
 	}
+
+	if err := os.Chdir(dir); err != nil {
+		t.Fatal(err)
+	}
+
+	// change to use self-signed TLS certificates
+	t.Logf("Setting Update.UseTLS = self-signed")
+
+	{
+		cfg := ti.readConfig(t)
+
+		cfg.Update.UseTLS = "self-signed"
+		t.Logf("Updated cfg.Update = %+v", cfg.Update)
+
+		ti.writeConfig(t, cfg)
+	}
+
+	fakeBuildTimestamp = "fake-update-2"
+	ctx = context.WithValue(context.Background(), packer.BuildTimestampOverride, fakeBuildTimestamp)
+	c = gok.Context{
+		Args: []string{
+			"--parent_dir", "gokrazy",
+			"-i", instanceName,
+			"update",
+			"--insecure", // only on first update after enabling self-signed TLS
+		},
+	}
+	t.Logf("running %q", append([]string{"<gok>"}, c.Args...))
+	if err := c.Execute(ctx); err != nil {
+		t.Fatalf("%v: %v", c.Args, err)
+	}
+	if err := os.Chdir(dir); err != nil {
+		t.Fatal(err)
+	}
+
+	t.Logf("first update succeeded, doing another update without --insecure")
+	fakeBuildTimestamp = "fake-update-3"
+	ctx = context.WithValue(context.Background(), packer.BuildTimestampOverride, fakeBuildTimestamp)
+	c = gok.Context{
+		Args: []string{
+			"--parent_dir", "gokrazy",
+			"-i", instanceName,
+			"update",
+		},
+	}
+	t.Logf("running %q", append([]string{"<gok>"}, c.Args...))
+	if err := c.Execute(ctx); err != nil {
+		t.Fatalf("%v: %v", c.Args, err)
+	}
+	if err := os.Chdir(dir); err != nil {
+		t.Fatal(err)
+	}
+
+	t.Logf("second update succeeded, doing another update after deleting the certificates (with --insecure)")
+	certPath, keyPath, err := tlsflag.CertificatePathsFor("self-signed", hostname)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Remove(certPath); err != nil {
+		t.Fatalf("deleting certificate: %v", err)
+	}
+	if err := os.Remove(keyPath); err != nil {
+		t.Fatalf("deleting certificate: %v", err)
+	}
+	fakeBuildTimestamp = "fake-update-4"
+	ctx = context.WithValue(context.Background(), packer.BuildTimestampOverride, fakeBuildTimestamp)
+	c = gok.Context{
+		Args: []string{
+			"--parent_dir", "gokrazy",
+			"-i", instanceName,
+			"update",
+			"--insecure", // because we deleted the certificate files
+		},
+	}
+	t.Logf("running %q", append([]string{"<gok>"}, c.Args...))
+	if err := c.Execute(ctx); err != nil {
+		t.Fatalf("%v: %v", c.Args, err)
+	}
+
 }

integration/gokupdate/integration_test.go

@@ -0,0 +1,97 @@
+package gokupdate_test
+
+import (
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strconv"
+	"testing"
+	"time"
+
+	"github.com/anatol/vmtest"
+)
+
+func effectiveGOARCH() string {
+	goarch := os.Getenv("GOARCH")
+	if goarch != "" {
+		return goarch
+	}
+	return runtime.GOARCH
+}
+
+// TODO: move to a gokrazy/internal/integrationtest package
+func Run(t *testing.T, qemuArgs []string) *vmtest.Qemu {
+	tempdir := t.TempDir()
+	diskImage := filepath.Join(tempdir, "gokrazy.img")
+	// diskImage := "/tmp/gokrazy.img" // for debugging
+
+	// TODO: use in-process gok overwrite
+	packer := exec.Command("gok",
+		"overwrite",
+		"--instance=hello",
+		"--parent_dir=gokrazy",
+		"--full="+diskImage,
+		"--target_storage_bytes="+strconv.Itoa(2*1024*1024*1024))
+	packer.Env = append(os.Environ(), "GOARCH=amd64")
+	packer.Stdout = os.Stdout
+	packer.Stderr = os.Stderr
+	log.Printf("%s", packer.Args)
+	if err := packer.Run(); err != nil {
+		t.Fatalf("%s: %v", packer.Args, err)
+	}
+
+	// Chosen to match internal/gok/vmrun.go
+	qemuArgs = append(qemuArgs,
+		//"-enable-kvm",
+		//"-cpu", "host",
+		"-nodefaults",
+		"-m", "1024",
+		// required! system gets stuck without -smp
+		"-smp", strconv.Itoa(max(runtime.NumCPU(), 2)),
+		"-device", "e1000,netdev=net0",
+		"-netdev", "user,id=net0,hostfwd=tcp::9080-:9080,hostfwd=tcp::9022-:22,hostfwd=tcp::9443-:9443",
+		// Use -drive instead of vmtest.QemuOptions.Disks because the latter
+		// results in wiring up the devices using SCSI in a way that the
+		// router7 kernel config does not support.
+		// TODO: update kernel config and switch to Disks:
+		"-boot", "order=d",
+		"-drive", "file="+diskImage+",format=raw",
+	)
+
+	// Do not use hardware acceleration on GitHub Actions,
+	// where there is no nested KVM available (by default).
+	if os.Getenv("GITHUB_ACTIONS") != "true" {
+		goarch := effectiveGOARCH()
+		if goarch == runtime.GOARCH {
+			// Hardware acceleration (in both cases) is only available for the
+			// native architecture, e.g. arm64 for M1 MacBooks.
+			switch runtime.GOOS {
+			case "linux":
+				qemuArgs = append(qemuArgs, "-accel", "kvm")
+			case "darwin":
+				qemuArgs = append(qemuArgs, "-accel", "hvf")
+			}
+		}
+	}
+
+	opts := vmtest.QemuOptions{
+		Architecture:    vmtest.QEMU_X86_64,
+		OperatingSystem: vmtest.OS_LINUX,
+		Params:          qemuArgs,
+		// Disks: []vmtest.QemuDisk{
+		// 	{
+		// 		Path:   diskImage,
+		// 		Format: "raw",
+		// 	},
+		// },
+		Verbose: testing.Verbose(),
+		Timeout: 30 * time.Minute,
+	}
+	qemu, err := vmtest.NewQemu(&opts)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return qemu
+}

internal/cap/License

@@ -0,0 +1,398 @@
+/* SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0-only */
+
+Unless otherwise *explicitly* stated, the following text describes the
+licensed conditions under which the contents of this libcap/cap release
+may be used and distributed.
+
+The licensed conditions are one or the other of these two Licenses:
+
+  - BSD 3-clause
+  - GPL v2.0
+
+-------------------------------------------------------------------------
+BSD 3-clause:
+-------------
+
+Redistribution and use in source and binary forms of libcap/cap, with
+or without modification, are permitted provided that the following
+conditions are met:
+
+1. Redistributions of source code must retain any existing copyright
+   notice, and this entire permission notice in its entirety,
+   including the disclaimer of warranties.
+
+2. Redistributions in binary form must reproduce all prior and current
+   copyright notices, this list of conditions, and the following
+   disclaimer in the documentation and/or other materials provided
+   with the distribution.
+
+3. The name of any author may not be used to endorse or promote
+   products derived from this software without their specific prior
+   written permission.
+
+THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
+WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
+INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
+TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+DAMAGE.
+
+-------------------------------------------------------------------------
+GPL v2.0:
+---------
+
+ALTERNATIVELY, this product may be distributed under the terms of the
+GNU General Public License (v2.0 - see below), in which case the
+provisions of the GNU GPL are required INSTEAD OF the above
+restrictions.  (This clause is necessary due to a potential conflict
+between the GNU GPL and the restrictions contained in a BSD-style
+copyright.)
+
+-------------------------
+Full text of gpl-2.0.txt:
+-------------------------
+
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 2, June 1991
+
+ Copyright (C) 1989, 1991 Free Software Foundation, Inc.,
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The licenses for most software are designed to take away your
+freedom to share and change it.  By contrast, the GNU General Public
+License is intended to guarantee your freedom to share and change free
+software--to make sure the software is free for all its users.  This
+General Public License applies to most of the Free Software
+Foundation's software and to any other program whose authors commit to
+using it.  (Some other Free Software Foundation software is covered by
+the GNU Lesser General Public License instead.)  You can apply it to
+your programs, too.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+this service if you wish), that you receive source code or can get it
+if you want it, that you can change the software or use pieces of it
+in new free programs; and that you know you can do these things.
+
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+anyone to deny you these rights or to ask you to surrender the rights.
+These restrictions translate to certain responsibilities for you if you
+distribute copies of the software, or if you modify it.
+
+  For example, if you distribute copies of such a program, whether
+gratis or for a fee, you must give the recipients all the rights that
+you have.  You must make sure that they, too, receive or can get the
+source code.  And you must show them these terms so they know their
+rights.
+
+  We protect your rights with two steps: (1) copyright the software, and
+(2) offer you this license which gives you legal permission to copy,
+distribute and/or modify the software.
+
+  Also, for each author's protection and ours, we want to make certain
+that everyone understands that there is no warranty for this free
+software.  If the software is modified by someone else and passed on, we
+want its recipients to know that what they have is not the original, so
+that any problems introduced by others will not reflect on the original
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+
+  Finally, any free program is threatened constantly by software
+patents.  We wish to avoid the danger that redistributors of a free
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+patent must be licensed for everyone's free use or not licensed at all.
+
+  The precise terms and conditions for copying, distribution and
+modification follow.
+
+                    GNU GENERAL PUBLIC LICENSE
+   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
+  0. This License applies to any program or other work which contains
+a notice placed by the copyright holder saying it may be distributed
+under the terms of this General Public License.  The "Program", below,
+refers to any such program or work, and a "work based on the Program"
+means either the Program or any derivative work under copyright law:
+that is to say, a work containing the Program or a portion of it,
+either verbatim or with modifications and/or translated into another
+language.  (Hereinafter, translation is included without limitation in
+the term "modification".)  Each licensee is addressed as "you".
+
+Activities other than copying, distribution and modification are not
+covered by this License; they are outside its scope.  The act of
+running the Program is not restricted, and the output from the Program
+is covered only if its contents constitute a work based on the
+Program (independent of having been made by running the Program).
+Whether that is true depends on what the Program does.
+
+  1. You may copy and distribute verbatim copies of the Program's
+source code as you receive it, in any medium, provided that you
+conspicuously and appropriately publish on each copy an appropriate
+copyright notice and disclaimer of warranty; keep intact all the
+notices that refer to this License and to the absence of any warranty;
+and give any other recipients of the Program a copy of this License
+along with the Program.
+
+You may charge a fee for the physical act of transferring a copy, and
+you may at your option offer warranty protection in exchange for a fee.
+
+  2. You may modify your copy or copies of the Program or any portion
+of it, thus forming a work based on the Program, and copy and
+distribute such modifications or work under the terms of Section 1
+above, provided that you also meet all of these conditions:
+
+    a) You must cause the modified files to carry prominent notices
+    stating that you changed the files and the date of any change.
+
+    b) You must cause any work that you distribute or publish, that in
+    whole or in part contains or is derived from the Program or any
+    part thereof, to be licensed as a whole at no charge to all third
+    parties under the terms of this License.
+
+    c) If the modified program normally reads commands interactively
+    when run, you must cause it, when started running for such
+    interactive use in the most ordinary way, to print or display an
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+    notice that there is no warranty (or else, saying that you provide
+    a warranty) and that users may redistribute the program under
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+    the Program is not required to print an announcement.)
+
+These requirements apply to the modified work as a whole.  If
+identifiable sections of that work are not derived from the Program,
+and can be reasonably considered independent and separate works in
+themselves, then this License, and its terms, do not apply to those
+sections when you distribute them as separate works.  But when you
+distribute the same sections as part of a whole which is a work based
+on the Program, the distribution of the whole must be on the terms of
+this License, whose permissions for other licensees extend to the
+entire whole, and thus to each and every part regardless of who wrote it.
+
+Thus, it is not the intent of this section to claim rights or contest
+your rights to work written entirely by you; rather, the intent is to
+exercise the right to control the distribution of derivative or
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+
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+with the Program (or with a work based on the Program) on a volume of
+a storage or distribution medium does not bring the other work under
+the scope of this License.
+
+  3. You may copy and distribute the Program (or a work based on it,
+under Section 2) in object code or executable form under the terms of
+Sections 1 and 2 above provided that you also do one of the following:
+
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+
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+
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+
+  9. The Free Software Foundation may publish revised and/or new versions
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+address new problems or concerns.
+
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+specifies a version number of this License which applies to it and "any
+later version", you have the option of following the terms and conditions
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+Software Foundation.  If the Program does not specify a version number of
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+
+  10. If you wish to incorporate parts of the Program into other free
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+
+                            NO WARRANTY
+
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+POSSIBILITY OF SUCH DAMAGES.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+convey the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+Also add information on how to contact you by electronic and paper mail.
+
+If the program is interactive, make it output a short notice like this
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+
+    Gnomovision version 69, Copyright (C) year name of author
+    Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, the commands you use may
+be called something other than `show w' and `show c'; they could even be
+mouse-clicks or menu items--whatever suits your program.
+
+You should also get your employer (if you work as a programmer) or your
+school, if any, to sign a "copyright disclaimer" for the program, if
+necessary.  Here is a sample; alter the names:
+
+  Yoyodyne, Inc., hereby disclaims all copyright interest in the program
+  `Gnomovision' (which makes passes at compilers) written by James Hacker.
+
+  <signature of Ty Coon>, 1 April 1989
+  Ty Coon, President of Vice
+
+This General Public License does not permit incorporating your program into
+proprietary programs.  If your program is a subroutine library, you may
+consider it more useful to permit linking proprietary applications with the
+library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.

internal/cap/README

@@ -0,0 +1,13 @@
+This package is modified from the libcap project to allow
+cross-platform marshalling to/from the kernel vfs format to write squashfs
+xattr values and for parsing the text format used with the setcap command
+
+Package cap is the libcap API for Linux Capabilities written in
+Go. The official release announcement site for libcap is:
+
+   https://sites.google.com/site/fullycapable/
+
+Like libcap, the cap package is distributed with a "you choose"
+License. Specifically: BSD 3-clause, or GPL2. See the License file.
+
+Andrew G. Morgan <morgan@kernel.org>

internal/cap/cap.go

@@ -0,0 +1,124 @@
+// Package cap
+// Copyright (c) 2019-21 Andrew G. Morgan <morgan@kernel.org>
+//
+// The cap and psx packages are licensed with a (you choose) BSD
+// 3-clause or GPL2. See LICENSE file for details.
+// [the Fully Capable site]: https://sites.google.com/site/fullycapable/
+package cap
+
+import (
+	"errors"
+	"sync"
+)
+
+// Value is the type of a single capability (or permission) bit.
+type Value uint
+
+// Flag is the type of one of the three Value dimensions held in a
+// Set.  It is also used in the (*IAB).Fill() method for changing the
+// Bounding and Ambient Vectors.
+type Flag uint
+
+// Effective, Permitted, Inheritable are the three Flags of Values
+// held in a Set.
+const (
+	Effective Flag = iota
+	Permitted
+	Inheritable
+)
+
+// String identifies a Flag value by its conventional "e", "p" or "i"
+// string abbreviation.
+func (f Flag) String() string {
+	switch f {
+	case Effective:
+		return "e"
+	case Permitted:
+		return "p"
+	case Inheritable:
+		return "i"
+	default:
+		return "<Error>"
+	}
+}
+
+// data holds a 32-bit slice of the compressed bitmaps of capability
+// sets as understood by the kernel.
+type data [Inheritable + 1]uint32
+
+// Set is an opaque capabilities container for a set of system
+// capbilities. It holds individually addressable capability Value's
+// for the three capability Flag's. See GetFlag() and SetFlag() for
+// how to adjust them individually, and Clear() and ClearFlag() for
+// how to do bulk operations.
+//
+// For admin tasks associated with managing namespace specific file
+// capabilities, Set can also support a namespace-root-UID value which
+// defaults to zero. See GetNSOwner() and SetNSOwner().
+type Set struct {
+	// mu protects all other members of a Set.
+	mu sync.RWMutex
+
+	// flat holds Flag Value bitmaps for all capabilities
+	// associated with this Set.
+	flat []data
+
+	// Linux specific
+	nsRoot int
+}
+
+// Various known kernel magic values.
+const (
+	kv1 = 0x19980330 // First iteration of process capabilities (32 bits).
+	kv2 = 0x20071026 // First iteration of process and file capabilities (64 bits) - deprecated.
+	kv3 = 0x20080522 // Most recently supported process and file capabilities (64 bits).
+)
+
+var (
+	// startUp protects setting of the following values: magic,
+	// words, maxValues.
+	startUp sync.Once
+
+	// magic holds the preferred magic number for the kernel ABI.
+	magic uint32
+
+	// words holds the number of uint32's associated with each
+	// capability Flag for this session.
+	words int
+
+	// maxValues holds the number of bit values that are named by
+	// the running kernel. This is generally expected to match
+	// ValueCount which is autogenerated at packaging time.
+	maxValues uint
+)
+
+type header struct {
+	magic uint32
+	pid   int32
+}
+
+// defines from uapi/linux/prctl.h
+const (
+	prCapBSetRead = 23
+	prCapBSetDrop = 24
+)
+
+// NewSet returns an empty capability set.
+func NewSet() *Set {
+	startUp.Do(cInit)
+	return &Set{
+		flat: make([]data, words),
+	}
+}
+
+// ErrBadSet indicates a nil pointer was used for a *Set, or the
+// request of the Set is invalid in some way.
+var ErrBadSet = errors.New("bad capability set")
+
+// good confirms that c looks valid.
+func (c *Set) good() error {
+	if c == nil || len(c.flat) == 0 {
+		return ErrBadSet
+	}
+	return nil
+}

internal/cap/cinit_linux.go

@@ -0,0 +1,47 @@
+//go:build linux
+
+package cap
+
+import (
+	"sort"
+	"syscall"
+	"unsafe"
+)
+
+// cInit performs the lazy identification of the capability vintage of
+// the running system.
+func cInit() {
+	h := &header{
+		magic: kv3,
+	}
+	_, _, _ = syscall.RawSyscall(syscall.SYS_CAPGET, uintptr(unsafe.Pointer(h)), uintptr(0), 0)
+
+	magic = h.magic
+	switch magic {
+	case kv1:
+		words = 1
+	case kv2, kv3:
+		words = 2
+	default:
+		// Fall back to a known good version.
+		magic = kv3
+		words = 2
+	}
+	// Use the bounding set to evaluate which capabilities exist.
+	maxValues = uint(sort.Search(32*words, func(n int) bool {
+		_, err := GetBound(Value(n))
+		return err != nil
+	}))
+	if maxValues == 0 {
+		// Fall back to using the largest value defined at build time.
+		maxValues = NamedCount
+	}
+}
+func GetBound(val Value) (bool, error) {
+	r, _, err := syscall.RawSyscall(syscall.SYS_PRCTL, prCapBSetRead, uintptr(val), 0)
+	if err != 0 {
+		return false, err
+	}
+
+	return int(r) > 0, nil
+}

internal/cap/cinit_other.go

@@ -0,0 +1,12 @@
+//go:build !linux
+
+package cap
+
+// cInit performs the lazy identification of the capability vintage of
+// the running system.
+func cInit() {
+	if maxValues == 0 {
+		// Fall back to using the largest value defined at build time.
+		maxValues = NamedCount
+	}
+}

internal/cap/file.go

@@ -0,0 +1,174 @@
+package cap
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"io"
+	"syscall"
+)
+
+// uapi/linux/xattr.h defined.
+var (
+	xattrNameCaps, _ = syscall.BytePtrFromString("security.capability")
+)
+
+// uapi/linux/capability.h defined.
+const (
+	vfsCapRevisionMask   = uint32(0xff000000)
+	vfsCapFlagsMask      = ^vfsCapRevisionMask
+	vfsCapFlagsEffective = uint32(1)
+
+	vfsCapRevision1 = uint32(0x01000000)
+	vfsCapRevision2 = uint32(0x02000000)
+	vfsCapRevision3 = uint32(0x03000000)
+)
+
+// Data types stored in little-endian order.
+
+type vfsCaps1 struct {
+	MagicEtc uint32
+	Data     [1]struct {
+		Permitted, Inheritable uint32
+	}
+}
+
+type vfsCaps2 struct {
+	MagicEtc uint32
+	Data     [2]struct {
+		Permitted, Inheritable uint32
+	}
+}
+
+type vfsCaps3 struct {
+	MagicEtc uint32
+	Data     [2]struct {
+		Permitted, Inheritable uint32
+	}
+	RootID uint32
+}
+
+// ErrBadSize indicates the loaded file capability has
+// an invalid number of bytes in it.
+var ErrBadSize = errors.New("filecap bad size")
+
+// ErrBadMagic indicates that the kernel preferred magic number for
+// capability Set values is not supported by this package. This
+// generally implies you are using an exceptionally old
+// "../libcap/cap" package. An upgrade is needed, or failing that see
+// [the Fully Capable site] for the way to report or review a bug.
+//
+// [the Fully Capable site]: https://sites.google.com/site/fullycapable/
+var ErrBadMagic = errors.New("unsupported magic")
+
+// ErrBadPath indicates a failed attempt to set a file capability on
+// an irregular (non-executable) file.
+var ErrBadPath = errors.New("file is not a regular executable")
+
+// ErrOutOfRange indicates an erroneous value for MinExtFlagSize.
+var ErrOutOfRange = errors.New("flag length invalid for export")
+
+// DigestFileCap unpacks a file capability and returns it in a *Set
+// form.
+func DigestFileCap(d []byte) (*Set, error) {
+	var (
+		err  error
+		raw1 vfsCaps1
+		raw2 vfsCaps2
+		raw3 vfsCaps3
+	)
+	sz := len(d)
+	if sz < binary.Size(raw1) || sz > binary.Size(raw3) {
+		return nil, ErrBadSize
+	}
+	b := bytes.NewReader(d)
+	var magicEtc uint32
+	if err = binary.Read(b, binary.LittleEndian, &magicEtc); err != nil {
+		return nil, err
+	}
+
+	c := NewSet()
+	b.Seek(0, io.SeekStart)
+	switch magicEtc & vfsCapRevisionMask {
+	case vfsCapRevision1:
+		if err = binary.Read(b, binary.LittleEndian, &raw1); err != nil {
+			return nil, err
+		}
+		data := raw1.Data[0]
+		c.flat[0][Permitted] = data.Permitted
+		c.flat[0][Inheritable] = data.Inheritable
+		if raw1.MagicEtc&vfsCapFlagsMask == vfsCapFlagsEffective {
+			c.flat[0][Effective] = data.Inheritable | data.Permitted
+		}
+	case vfsCapRevision2:
+		if err = binary.Read(b, binary.LittleEndian, &raw2); err != nil {
+			return nil, err
+		}
+		for i, data := range raw2.Data {
+			c.flat[i][Permitted] = data.Permitted
+			c.flat[i][Inheritable] = data.Inheritable
+			if raw2.MagicEtc&vfsCapFlagsMask == vfsCapFlagsEffective {
+				c.flat[i][Effective] = data.Inheritable | data.Permitted
+			}
+		}
+	case vfsCapRevision3:
+		if err = binary.Read(b, binary.LittleEndian, &raw3); err != nil {
+			return nil, err
+		}
+		for i, data := range raw3.Data {
+			c.flat[i][Permitted] = data.Permitted
+			c.flat[i][Inheritable] = data.Inheritable
+			if raw3.MagicEtc&vfsCapFlagsMask == vfsCapFlagsEffective {
+				c.flat[i][Effective] = data.Inheritable | data.Permitted
+			}
+		}
+		c.nsRoot = int(raw3.RootID)
+	default:
+		return nil, ErrBadMagic
+	}
+	return c, nil
+}
+
+// PackFileCap transforms a system capability into a VFS form. Because
+// of the way Linux stores capabilities in the file extended
+// attributes, the process is a little lossy with respect to effective
+// bits.
+func (c *Set) PackFileCap() ([]byte, error) {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+
+	var magic uint32
+	switch words {
+	case 1:
+		if c.nsRoot != 0 {
+			return nil, ErrBadSet // nsRoot not supported for single DWORD caps.
+		}
+		magic = vfsCapRevision1
+	case 2:
+		if c.nsRoot == 0 {
+			magic = vfsCapRevision2
+			break
+		}
+		magic = vfsCapRevision3
+	}
+	if magic == 0 {
+		return nil, ErrBadSize
+	}
+	eff := uint32(0)
+	for _, f := range c.flat {
+		eff |= (f[Permitted] | f[Inheritable]) & f[Effective]
+	}
+	if eff != 0 {
+		magic |= vfsCapFlagsEffective
+	}
+	b := new(bytes.Buffer)
+	binary.Write(b, binary.LittleEndian, magic)
+	for _, f := range c.flat {
+		binary.Write(b, binary.LittleEndian, f[Permitted])
+		binary.Write(b, binary.LittleEndian, f[Inheritable])
+	}
+	if c.nsRoot != 0 {
+		binary.Write(b, binary.LittleEndian, uint32(c.nsRoot))
+	}
+	return b.Bytes(), nil
+}

internal/cap/flags.go

@@ -0,0 +1,134 @@
+package cap
+
+import "errors"
+
+// GetFlag determines if the requested Value is enabled in the
+// specified Flag of the capability Set.
+func (c *Set) GetFlag(vec Flag, val Value) (bool, error) {
+	if err := c.good(); err != nil {
+		// Checked this first, because otherwise we are sure
+		// cInit has been called.
+		return false, err
+	}
+	offset, mask, err := bitOf(vec, val)
+	if err != nil {
+		return false, err
+	}
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	return c.flat[offset][vec]&mask != 0, nil
+}
+
+// SetFlag sets the requested bits to the indicated enable state. This
+// function does not perform any security checks, so values can be set
+// out-of-order. Only when the Set is used to SetProc() etc., will the
+// bits be checked for validity and permission by the kernel. If the
+// function returns an error, the Set will not be modified.
+func (c *Set) SetFlag(vec Flag, enable bool, val ...Value) error {
+	if err := c.good(); err != nil {
+		// Checked this first, because otherwise we are sure
+		// cInit has been called.
+		return err
+	}
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	// Make a backup.
+	replace := make([]uint32, words)
+	for i := range replace {
+		replace[i] = c.flat[i][vec]
+	}
+	var err error
+	for _, v := range val {
+		offset, mask, err2 := bitOf(vec, v)
+		if err2 != nil {
+			err = err2
+			break
+		}
+		if enable {
+			c.flat[offset][vec] |= mask
+		} else {
+			c.flat[offset][vec] &= ^mask
+		}
+	}
+	if err == nil {
+		return nil
+	}
+	// Clean up.
+	for i, bits := range replace {
+		c.flat[i][vec] = bits
+	}
+	return err
+}
+
+// Clear fully clears a capability set.
+func (c *Set) Clear() error {
+	if err := c.good(); err != nil {
+		return err
+	}
+	// startUp.Do(cInit) is not called here because c cannot be
+	// initialized except via this package and doing that will
+	// perform that call at least once (sic).
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.flat = make([]data, words)
+	c.nsRoot = 0
+	return nil
+}
+
+// ErrBadValue indicates a bad capability value was specified.
+var ErrBadValue = errors.New("bad capability value")
+
+// bitOf converts from a Value into the offset and mask for a specific
+// Value bit in the compressed (kernel ABI) representation of a
+// capabilities. If the requested bit is unsupported, an error is
+// returned.
+func bitOf(vec Flag, val Value) (uint, uint32, error) {
+	if vec > Inheritable || val > Value(words*32) {
+		return 0, 0, ErrBadValue
+	}
+	u := uint(val)
+	return u / 32, uint32(1) << (u % 32), nil
+}
+
+// allMask returns the mask of valid bits in the all mask for index.
+func allMask(index uint) (mask uint32) {
+	if maxValues == 0 {
+		panic("uninitialized package")
+	}
+	base := 32 * uint(index)
+	if maxValues <= base {
+		return
+	}
+	if maxValues >= 32+base {
+		mask = ^mask
+		return
+	}
+	mask = uint32((uint64(1) << (maxValues % 32)) - 1)
+	return
+}
+
+// forceFlag sets 'all' capability values (supported by the kernel) of
+// a specified Flag to enable.
+func (c *Set) forceFlag(vec Flag, enable bool) error {
+	if err := c.good(); err != nil {
+		return err
+	}
+	if vec > Inheritable {
+		return ErrBadSet
+	}
+	m := uint32(0)
+	if enable {
+		m = ^m
+	}
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	for i := range c.flat {
+		c.flat[i][vec] = m & allMask(uint(i))
+	}
+	return nil
+}
+
+// ClearFlag clears all the Values associated with the specified Flag.
+func (c *Set) ClearFlag(vec Flag) error {
+	return c.forceFlag(vec, false)
+}

internal/cap/names.go

@@ -0,0 +1,440 @@
+package cap
+
+/* ** DO NOT EDIT THIS FILE. IT WAS AUTO-GENERATED BY LIBCAP'S GO BUILDER (mknames.go) ** */
+
+// NamedCount holds the number of capability values, with official
+// names, known at the time this libcap/cap version was released. The
+// "../libcap/cap" package is fully able to manipulate higher numbered
+// capability values by numerical value. However, if you find
+// cap.NamedCount < cap.MaxBits(), it is probably time to upgrade this
+// package on your system.
+//
+// FWIW the userspace tool '/sbin/capsh' also contains a runtime check
+// for the condition that libcap is behind the running kernel in this
+// way.
+const NamedCount = 41
+
+// CHOWN etc., are the named capability values of the Linux
+// kernel. The canonical source for each name is the
+// "uapi/linux/capabilities.h" file.  Some values may not be available
+// (yet) where the kernel is older.  The actual number of capabities
+// supported by the running kernel can be obtained using the
+// cap.MaxBits() function.
+const (
+	// CHOWN allows a process to arbitrarily change the user and
+	// group ownership of a file.
+	CHOWN Value = iota
+
+	// DAC_OVERRIDE allows a process to override of all Discretionary
+	// Access Control (DAC) access, including ACL execute
+	// access. That is read, write or execute files that the
+	// process would otherwise not have access to. This
+	// excludes DAC access covered by cap.LINUX_IMMUTABLE.
+	DAC_OVERRIDE
+
+	// DAC_READ_SEARCH allows a process to override all DAC restrictions
+	// limiting the read and search of files and
+	// directories. This excludes DAC access covered by
+	// cap.LINUX_IMMUTABLE.
+	DAC_READ_SEARCH
+
+	// FOWNER allows a process to perform operations on files, even
+	// where file owner ID should otherwise need be equal to
+	// the UID, except where cap.FSETID is applicable. It
+	// doesn't override MAC and DAC restrictions.
+	//
+	// This capability permits the deletion of a file owned
+	// by another UID in a directory protected by the sticky
+	// (t) bit.
+	FOWNER
+
+	// FSETID allows a process to set the S_ISUID and S_ISUID bits of
+	// the file permissions, even when the process' effective
+	// UID or GID/supplementary GIDs do not match that of the
+	// file.
+	FSETID
+
+	// KILL allows a process to send a kill(2) signal to any other
+	// process - overriding the limitation that there be a
+	// [E]UID match between source and target process.
+	KILL
+
+	// SETGID allows a process to freely manipulate its own GIDs:
+	//   - arbitrarily set the GID, EGID, REGID, RESGID values
+	//   - arbitrarily set the supplementary GIDs
+	//   - allows the forging of GID credentials passed over a
+	//     socket
+	SETGID
+
+	// SETUID allows a process to freely manipulate its own UIDs:
+	//   - arbitrarily set the UID, EUID, REUID and RESUID
+	//     values
+	//   - allows the forging of UID credentials passed over a
+	//     socket
+	SETUID
+
+	// SETPCAP allows a process to freely manipulate its inheritable
+	// capabilities.
+	//
+	// Linux supports the POSIX.1e Inheritable set, the POXIX.1e (X
+	// vector) known in Linux as the Bounding vector, as well as
+	// the Linux extension Ambient vector.
+	//
+	// This capability permits dropping bits from the Bounding
+	// vector (ie. raising B bits in the libcap IAB
+	// representation). It also permits the process to raise
+	// Ambient vector bits that are both raised in the Permitted
+	// and Inheritable sets of the process. This capability cannot
+	// be used to raise Permitted bits, Effective bits beyond those
+	// already present in the process' permitted set, or
+	// Inheritable bits beyond those present in the Bounding
+	// vector.
+	//
+	// [Historical note: prior to the advent of file capabilities
+	// (2008), this capability was suppressed by default, as its
+	// unsuppressed behavior was not auditable: it could
+	// asynchronously grant its own Permitted capabilities to and
+	// remove capabilities from other processes arbitrarily. The
+	// former leads to undefined behavior, and the latter is better
+	// served by the kill system call.]
+	SETPCAP
+
+	// LINUX_IMMUTABLE allows a process to modify the S_IMMUTABLE and
+	// S_APPEND file attributes.
+	LINUX_IMMUTABLE
+
+	// NET_BIND_SERVICE allows a process to bind to privileged ports:
+	//   - TCP/UDP sockets below 1024
+	//   - ATM VCIs below 32
+	NET_BIND_SERVICE
+
+	// NET_BROADCAST allows a process to broadcast to the network and to
+	// listen to multicast.
+	NET_BROADCAST
+
+	// NET_ADMIN allows a process to perform network configuration
+	// operations:
+	//   - interface configuration
+	//   - administration of IP firewall, masquerading and
+	//     accounting
+	//   - setting debug options on sockets
+	//   - modification of routing tables
+	//   - setting arbitrary process, and process group
+	//     ownership on sockets
+	//   - binding to any address for transparent proxying
+	//     (this is also allowed via cap.NET_RAW)
+	//   - setting TOS (Type of service)
+	//   - setting promiscuous mode
+	//   - clearing driver statistics
+	//   - multicasing
+	//   - read/write of device-specific registers
+	//   - activation of ATM control sockets
+	NET_ADMIN
+
+	// NET_RAW allows a process to use raw networking:
+	//   - RAW sockets
+	//   - PACKET sockets
+	//   - binding to any address for transparent proxying
+	//     (also permitted via cap.NET_ADMIN)
+	NET_RAW
+
+	// IPC_LOCK allows a process to lock shared memory segments for IPC
+	// purposes.  Also enables mlock and mlockall system
+	// calls.
+	IPC_LOCK
+
+	// IPC_OWNER allows a process to override IPC ownership checks.
+	IPC_OWNER
+
+	// SYS_MODULE allows a process to initiate the loading and unloading
+	// of kernel modules. This capability can effectively
+	// modify kernel without limit.
+	SYS_MODULE
+
+	// SYS_RAWIO allows a process to perform raw IO:
+	//   - permit ioper/iopl access
+	//   - permit sending USB messages to any device via
+	//     /dev/bus/usb
+	SYS_RAWIO
+
+	// SYS_CHROOT allows a process to perform a chroot syscall to change
+	// the effective root of the process' file system:
+	// redirect to directory "/" to some other location.
+	SYS_CHROOT
+
+	// SYS_PTRACE allows a process to perform a ptrace() of any other
+	// process.
+	SYS_PTRACE
+
+	// SYS_PACCT allows a process to configure process accounting.
+	SYS_PACCT
+
+	// SYS_ADMIN allows a process to perform a somewhat arbitrary
+	// grab-bag of privileged operations. Over time, this
+	// capability should weaken as specific capabilities are
+	// created for subsets of cap.SYS_ADMINs functionality:
+	//   - configuration of the secure attention key
+	//   - administration of the random device
+	//   - examination and configuration of disk quotas
+	//   - setting the domainname
+	//   - setting the hostname
+	//   - calling bdflush()
+	//   - mount() and umount(), setting up new SMB connection
+	//   - some autofs root ioctls
+	//   - nfsservctl
+	//   - VM86_REQUEST_IRQ
+	//   - to read/write pci config on alpha
+	//   - irix_prctl on mips (setstacksize)
+	//   - flushing all cache on m68k (sys_cacheflush)
+	//   - removing semaphores
+	//   - Used instead of cap.CHOWN to "chown" IPC message
+	//     queues, semaphores and shared memory
+	//   - locking/unlocking of shared memory segment
+	//   - turning swap on/off
+	//   - forged pids on socket credentials passing
+	//   - setting readahead and flushing buffers on block
+	//     devices
+	//   - setting geometry in floppy driver
+	//   - turning DMA on/off in xd driver
+	//   - administration of md devices (mostly the above, but
+	//     some extra ioctls)
+	//   - tuning the ide driver
+	//   - access to the nvram device
+	//   - administration of apm_bios, serial and bttv (TV)
+	//     device
+	//   - manufacturer commands in isdn CAPI support driver
+	//   - reading non-standardized portions of PCI
+	//     configuration space
+	//   - DDI debug ioctl on sbpcd driver
+	//   - setting up serial ports
+	//   - sending raw qic-117 commands
+	//   - enabling/disabling tagged queuing on SCSI
+	//     controllers and sending arbitrary SCSI commands
+	//   - setting encryption key on loopback filesystem
+	//   - setting zone reclaim policy
+	SYS_ADMIN
+
+	// SYS_BOOT allows a process to initiate a reboot of the system.
+	SYS_BOOT
+
+	// SYS_NICE allows a process to maipulate the execution priorities
+	// of arbitrary processes:
+	//   - those involving different UIDs
+	//   - setting their CPU affinity
+	//   - alter the FIFO vs. round-robin (realtime)
+	//     scheduling for itself and other processes.
+	SYS_NICE
+
+	// SYS_RESOURCE allows a process to adjust resource related parameters
+	// of processes and the system:
+	//   - set and override resource limits
+	//   - override quota limits
+	//   - override the reserved space on ext2 filesystem
+	//     (this can also be achieved via cap.FSETID)
+	//   - modify the data journaling mode on ext3 filesystem,
+	//     which uses journaling resources
+	//   - override size restrictions on IPC message queues
+	//   - configure more than 64Hz interrupts from the
+	//     real-time clock
+	//   - override the maximum number of consoles for console
+	//     allocation
+	//   - override the maximum number of keymaps
+	SYS_RESOURCE
+
+	// SYS_TIME allows a process to perform time manipulation of clocks:
+	//   - alter the system clock
+	//   - enable irix_stime on MIPS
+	//   - set the real-time clock
+	SYS_TIME
+
+	// SYS_TTY_CONFIG allows a process to manipulate tty devices:
+	//   - configure tty devices
+	//   - perform vhangup() of a tty
+	SYS_TTY_CONFIG
+
+	// MKNOD allows a process to perform privileged operations with
+	// the mknod() system call.
+	MKNOD
+
+	// LEASE allows a process to take leases on files.
+	LEASE
+
+	// AUDIT_WRITE allows a process to write to the audit log via a
+	// unicast netlink socket.
+	AUDIT_WRITE
+
+	// AUDIT_CONTROL allows a process to configure audit logging via a
+	// unicast netlink socket.
+	AUDIT_CONTROL
+
+	// SETFCAP allows a process to set capabilities on files.
+	// Permits a process to uid_map the uid=0 of the
+	// parent user namespace into that of the child
+	// namespace. Also, permits a process to override
+	// securebits locks through user namespace
+	// creation.
+	SETFCAP
+
+	// MAC_OVERRIDE allows a process to override Manditory Access Control
+	// (MAC) access. Not all kernels are configured with a MAC
+	// mechanism, but this is the capability reserved for
+	// overriding them.
+	MAC_OVERRIDE
+
+	// MAC_ADMIN allows a process to configure the Mandatory Access
+	// Control (MAC) policy. Not all kernels are configured
+	// with a MAC enabled, but if they are this capability is
+	// reserved for code to perform administration tasks.
+	MAC_ADMIN
+
+	// SYSLOG allows a process to configure the kernel's syslog
+	// (printk) behavior.
+	SYSLOG
+
+	// WAKE_ALARM allows a process to trigger something that can wake the
+	// system up.
+	WAKE_ALARM
+
+	// BLOCK_SUSPEND allows a process to block system suspends - prevent the
+	// system from entering a lower power state.
+	BLOCK_SUSPEND
+
+	// AUDIT_READ allows a process to read the audit log via a multicast
+	// netlink socket.
+	AUDIT_READ
+
+	// PERFMON allows a process to enable observability of privileged
+	// operations related to performance. The mechanisms
+	// include perf_events, i915_perf and other kernel
+	// subsystems.
+	PERFMON
+
+	// BPF allows a process to manipulate aspects of the kernel
+	// enhanced Berkeley Packet Filter (BPF) system. This is
+	// an execution subsystem of the kernel, that manages BPF
+	// programs. cap.BPF permits a process to:
+	//   - create all types of BPF maps
+	//   - advanced verifier features:
+	//     - indirect variable access
+	//     - bounded loops
+	//     - BPF to BPF function calls
+	//     - scalar precision tracking
+	//     - larger complexity limits
+	//     - dead code elimination
+	//     - potentially other features
+	//
+	// Other capabilities can be used together with cap.BFP to
+	// further manipulate the BPF system:
+	//   - cap.PERFMON relaxes the verifier checks as follows:
+	//     - BPF programs can use pointer-to-integer
+	//       conversions
+	//     - speculation attack hardening measures can be
+	//       bypassed
+	//     - bpf_probe_read to read arbitrary kernel memory is
+	//       permitted
+	//     - bpf_trace_printk to print the content of kernel
+	//       memory
+	//   - cap.SYS_ADMIN permits the following:
+	//     - use of bpf_probe_write_user
+	//     - iteration over the system-wide loaded programs,
+	//       maps, links BTFs and convert their IDs to file
+	//       descriptors.
+	//   - cap.PERFMON is required to load tracing programs.
+	//   - cap.NET_ADMIN is required to load networking
+	//     programs.
+	BPF
+
+	// CHECKPOINT_RESTORE allows a process to perform checkpoint
+	// and restore operations. Also permits
+	// explicit PID control via clone3() and
+	// also writing to ns_last_pid.
+	CHECKPOINT_RESTORE
+)
+
+var names = map[Value]string{
+	CHOWN:              "cap_chown",
+	DAC_OVERRIDE:       "cap_dac_override",
+	DAC_READ_SEARCH:    "cap_dac_read_search",
+	FOWNER:             "cap_fowner",
+	FSETID:             "cap_fsetid",
+	KILL:               "cap_kill",
+	SETGID:             "cap_setgid",
+	SETUID:             "cap_setuid",
+	SETPCAP:            "cap_setpcap",
+	LINUX_IMMUTABLE:    "cap_linux_immutable",
+	NET_BIND_SERVICE:   "cap_net_bind_service",
+	NET_BROADCAST:      "cap_net_broadcast",
+	NET_ADMIN:          "cap_net_admin",
+	NET_RAW:            "cap_net_raw",
+	IPC_LOCK:           "cap_ipc_lock",
+	IPC_OWNER:          "cap_ipc_owner",
+	SYS_MODULE:         "cap_sys_module",
+	SYS_RAWIO:          "cap_sys_rawio",
+	SYS_CHROOT:         "cap_sys_chroot",
+	SYS_PTRACE:         "cap_sys_ptrace",
+	SYS_PACCT:          "cap_sys_pacct",
+	SYS_ADMIN:          "cap_sys_admin",
+	SYS_BOOT:           "cap_sys_boot",
+	SYS_NICE:           "cap_sys_nice",
+	SYS_RESOURCE:       "cap_sys_resource",
+	SYS_TIME:           "cap_sys_time",
+	SYS_TTY_CONFIG:     "cap_sys_tty_config",
+	MKNOD:              "cap_mknod",
+	LEASE:              "cap_lease",
+	AUDIT_WRITE:        "cap_audit_write",
+	AUDIT_CONTROL:      "cap_audit_control",
+	SETFCAP:            "cap_setfcap",
+	MAC_OVERRIDE:       "cap_mac_override",
+	MAC_ADMIN:          "cap_mac_admin",
+	SYSLOG:             "cap_syslog",
+	WAKE_ALARM:         "cap_wake_alarm",
+	BLOCK_SUSPEND:      "cap_block_suspend",
+	AUDIT_READ:         "cap_audit_read",
+	PERFMON:            "cap_perfmon",
+	BPF:                "cap_bpf",
+	CHECKPOINT_RESTORE: "cap_checkpoint_restore",
+}
+
+var bits = map[string]Value{
+	"cap_chown":              CHOWN,
+	"cap_dac_override":       DAC_OVERRIDE,
+	"cap_dac_read_search":    DAC_READ_SEARCH,
+	"cap_fowner":             FOWNER,
+	"cap_fsetid":             FSETID,
+	"cap_kill":               KILL,
+	"cap_setgid":             SETGID,
+	"cap_setuid":             SETUID,
+	"cap_setpcap":            SETPCAP,
+	"cap_linux_immutable":    LINUX_IMMUTABLE,
+	"cap_net_bind_service":   NET_BIND_SERVICE,
+	"cap_net_broadcast":      NET_BROADCAST,
+	"cap_net_admin":          NET_ADMIN,
+	"cap_net_raw":            NET_RAW,
+	"cap_ipc_lock":           IPC_LOCK,
+	"cap_ipc_owner":          IPC_OWNER,
+	"cap_sys_module":         SYS_MODULE,
+	"cap_sys_rawio":          SYS_RAWIO,
+	"cap_sys_chroot":         SYS_CHROOT,
+	"cap_sys_ptrace":         SYS_PTRACE,
+	"cap_sys_pacct":          SYS_PACCT,
+	"cap_sys_admin":          SYS_ADMIN,
+	"cap_sys_boot":           SYS_BOOT,
+	"cap_sys_nice":           SYS_NICE,
+	"cap_sys_resource":       SYS_RESOURCE,
+	"cap_sys_time":           SYS_TIME,
+	"cap_sys_tty_config":     SYS_TTY_CONFIG,
+	"cap_mknod":              MKNOD,
+	"cap_lease":              LEASE,
+	"cap_audit_write":        AUDIT_WRITE,
+	"cap_audit_control":      AUDIT_CONTROL,
+	"cap_setfcap":            SETFCAP,
+	"cap_mac_override":       MAC_OVERRIDE,
+	"cap_mac_admin":          MAC_ADMIN,
+	"cap_syslog":             SYSLOG,
+	"cap_wake_alarm":         WAKE_ALARM,
+	"cap_block_suspend":      BLOCK_SUSPEND,
+	"cap_audit_read":         AUDIT_READ,
+	"cap_perfmon":            PERFMON,
+	"cap_bpf":                BPF,
+	"cap_checkpoint_restore": CHECKPOINT_RESTORE,
+}

internal/cap/text.go

@@ -0,0 +1,328 @@
+package cap
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// String converts a capability Value into its canonical text
+// representation.
+func (v Value) String() string {
+	name, ok := names[v]
+	if ok {
+		return name
+	}
+	// Un-named capabilities are referred to numerically (in decimal).
+	return strconv.Itoa(int(v))
+}
+
+// FromName converts a named capability Value to its binary
+// representation.
+func FromName(name string) (Value, error) {
+	startUp.Do(cInit)
+	v, ok := bits[name]
+	if ok {
+		if v >= Value(words*32) {
+			return 0, ErrBadValue
+		}
+		return v, nil
+	}
+	i, err := strconv.Atoi(name)
+	if err != nil {
+		return 0, err
+	}
+	if i >= 0 && i < int(words*32) {
+		return Value(i), nil
+	}
+	return 0, ErrBadValue
+}
+
+const (
+	eBin uint = (1 << Effective)
+	pBin      = (1 << Permitted)
+	iBin      = (1 << Inheritable)
+)
+
+var combos = []string{"", "e", "p", "ep", "i", "ei", "ip", "eip"}
+
+// histo generates a histogram of flag state combinations.
+// Note: c is locked by or private to the caller.
+func (c *Set) histo(bins []int, patterns []uint, from, limit Value) uint {
+	for v := from; v < limit; v++ {
+		b := uint(v & 31)
+		u, bit, err := bitOf(0, v)
+		if err != nil {
+			break
+		}
+		x := uint((c.flat[u][Effective]&bit)>>b) * eBin
+		x |= uint((c.flat[u][Permitted]&bit)>>b) * pBin
+		x |= uint((c.flat[u][Inheritable]&bit)>>b) * iBin
+		bins[x]++
+		patterns[uint(v)] = x
+	}
+	// Note, in the loop, we use >= to pick the smallest value for
+	// m with the highest bin value. That is ties break towards
+	// m=0.
+	m := uint(7)
+	for t := m; t > 0; {
+		t--
+		if bins[t] >= bins[m] {
+			m = t
+		}
+	}
+	return m
+}
+
+// String converts a full capability Set into a single short readable
+// string representation (which may contain spaces). See the
+// cap.FromText() function for an explanation of its return values.
+//
+// Note (*cap.Set).String() may evolve to generate more compact
+// strings representing the a given Set over time, but it should
+// maintain compatibility with the libcap:cap_to_text() function for
+// any given release. Further, it will always be an inverse of
+// cap.FromText().
+func (c *Set) String() string {
+	if err := c.good(); err != nil {
+		return "<invalid>"
+	}
+	bins := make([]int, 8)
+	patterns := make([]uint, maxValues)
+
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+
+	// Note, in order to have a *Set pointer, startUp.Do(cInit)
+	// must have been called which sets maxValues.
+	m := c.histo(bins, patterns, 0, Value(maxValues))
+
+	// Background state is the most popular of the named bits.
+	vs := []string{"=" + combos[m]}
+	for i := uint(8); i > 0; {
+		i--
+		if i == m || bins[i] == 0 {
+			continue
+		}
+		var list []string
+		for j, p := range patterns {
+			if p != i {
+				continue
+			}
+			list = append(list, Value(j).String())
+		}
+		x := strings.Join(list, ",")
+		var y, z string
+		if cf := i & ^m; cf != 0 {
+			op := "+"
+			if len(vs) == 1 && vs[0] == "=" {
+				// Special case "= foo+..." == "foo=...".
+				// Prefer because it
+				vs = nil
+				op = "="
+			}
+			y = op + combos[cf]
+		}
+		if cf := m & ^i; cf != 0 {
+			z = "-" + combos[cf]
+		}
+		vs = append(vs, x+y+z)
+	}
+
+	// The unnamed bits can only add to the above named ones since
+	// unnamed ones are always defaulted to lowered.
+	uBins := make([]int, 8)
+	uPatterns := make([]uint, 32*words)
+	c.histo(uBins, uPatterns, Value(maxValues), 32*Value(words))
+	for i := uint(7); i > 0; i-- {
+		if uBins[i] == 0 {
+			continue
+		}
+		var list []string
+		for j, p := range uPatterns {
+			if p != i {
+				continue
+			}
+			list = append(list, Value(j).String())
+		}
+		vs = append(vs, strings.Join(list, ",")+"+"+combos[i])
+	}
+
+	return strings.Join(vs, " ")
+}
+
+// ErrBadText is returned if the text for a capability set cannot be parsed.
+var ErrBadText = errors.New("bad text")
+
+// FromText converts the canonical text representation for a Set into
+// a freshly allocated Set.
+//
+// The format follows the following pattern: a set of space separated
+// sequences. Each sequence applies over the previous sequence to
+// build up a Set. The format of a sequence is:
+//
+//	[comma list of cap_values][[ops][flags]]*
+//
+// Examples:
+//
+//	"all=ep"
+//	"cap_chown,cap_setuid=ip cap_setuid+e"
+//	"=p cap_setpcap-p+i"
+//
+// Here "all" refers to all named capabilities known to the hosting
+// kernel, and "all" is assumed if no capabilities are listed before
+// an "=".
+//
+// The ops values, "=", "+" and "-" imply "reset and raise", "raise"
+// and "lower" respectively. The "e", "i" and "p" characters
+// correspond to the capabilities of the corresponding Flag: "e"
+// (Effective); "i" (Inheritable); "p" (Permitted).
+//
+// This syntax is overspecified and there are many ways of building
+// the same final Set state. Any sequence that includes a '=' resets
+// the accumulated state of all Flags ignoring earlier sequences. On
+// each of the following lines we give three or more examples of ways
+// to specify a common Set. The last entry on each line is the one
+// generated by (*cap.Set).String() from that Set.
+//
+//	"=p all+ei"  "all=pie"   "=pi all+e"   "=eip"
+//
+//	"cap_setuid=p cap_chown=i"  "cap_chown=ip-p"   "cap_chown=i"
+//
+//	"cap_chown=-p"   "all="   "cap_setuid=pie-pie"   "="
+//
+// Note: FromText() is tested at release time to completely match the
+// import ability of the libcap:cap_from_text() function.
+func FromText(text string) (*Set, error) {
+	text = strings.ToLower(text)
+	c := NewSet()
+	scanner := bufio.NewScanner(strings.NewReader(text))
+	scanner.Split(bufio.ScanWords)
+	chunks := 0
+	for scanner.Scan() {
+		chunks++
+
+		// Parsing for xxx([-+=][eip]+)+
+		t := scanner.Text()
+		i := strings.IndexAny(t, "=+-")
+		if i < 0 {
+			return nil, fmt.Errorf("%w: needs one of [=+-]", ErrBadText)
+		}
+		var vs []Value
+		sep := t[i]
+		if vals := t[:i]; vals == "all" {
+			for v := Value(0); v < Value(maxValues); v++ {
+				vs = append(vs, v)
+			}
+		} else if vals != "" {
+			for name := range strings.SplitSeq(vals, ",") {
+				v, err := FromName(name)
+				if err != nil {
+					return nil, fmt.Errorf("%w: %w", ErrBadText, err)
+				}
+				vs = append(vs, v)
+			}
+		} else if sep != '=' {
+			if vals == "" {
+				// Only "=" supports ""=="all".
+				return nil, ErrBadText
+			}
+		} else if j := i + 1; j+1 < len(t) {
+			switch t[j] {
+			case '+':
+				sep = 'P'
+				i++
+			case '-':
+				sep = 'M'
+				i++
+			}
+		}
+		i++
+
+		// There are 5 ways to set: =, =+, =-, +, -. We call
+		// the 2nd and 3rd of these 'P' and 'M'.
+
+		for {
+			// read [eip]+ setting flags.
+			var fE, fP, fI bool
+			for ok := true; ok && i < len(t); i++ {
+				switch t[i] {
+				case 'e':
+					fE = true
+				case 'i':
+					fI = true
+				case 'p':
+					fP = true
+				default:
+					ok = false
+				}
+				if !ok {
+					break
+				}
+			}
+
+			if !(fE || fI || fP) {
+				if sep != '=' {
+					return nil, fmt.Errorf("%w: needs one of [eip]", ErrBadText)
+				}
+			}
+
+			switch sep {
+			case '=', 'P', 'M', '+':
+				if sep != '+' {
+					c.Clear()
+					if sep == 'M' {
+						break
+					}
+				}
+				if keep := len(vs) == 0; keep {
+					if sep != '=' {
+						return nil, fmt.Errorf("%w: expected an '='", ErrBadText)
+					}
+					c.forceFlag(Effective, fE)
+					c.forceFlag(Permitted, fP)
+					c.forceFlag(Inheritable, fI)
+					break
+				}
+				// =, + and P for specific values are left.
+				if fE {
+					c.SetFlag(Effective, true, vs...)
+				}
+				if fP {
+					c.SetFlag(Permitted, true, vs...)
+				}
+				if fI {
+					c.SetFlag(Inheritable, true, vs...)
+				}
+			case '-':
+				if fE {
+					c.SetFlag(Effective, false, vs...)
+				}
+				if fP {
+					c.SetFlag(Permitted, false, vs...)
+				}
+				if fI {
+					c.SetFlag(Inheritable, false, vs...)
+				}
+			}
+
+			if i == len(t) {
+				break
+			}
+
+			switch t[i] {
+			case '+', '-':
+				sep = t[i]
+				i++
+			default:
+				return nil, fmt.Errorf("%w: expected '+' or '-'", ErrBadText)
+			}
+		}
+	}
+	if chunks == 0 {
+		return nil, fmt.Errorf("%w: No capabilities found", ErrBadText)
+	}
+	return c, nil
+}

internal/eeprom/eeprom.go

@@ -0,0 +1,129 @@
+// Package eeprom implements the Raspberry Pi EEPROM update file format.
+package eeprom
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"strings"
+)
+
+// Other implementations:
+//
+// - https://github.com/raspberrypi/rpi-eeprom (Python)
+// - https://github.com/info-beamer/rpi-eeprom-tools (Python)
+
+const (
+	MAGIC            = 0x55aaf00f
+	MAGIC_MASK       = 0xfffff00f
+	FILE_MAGIC       = 0x55aaf11f // id for modifiable files
+	FILENAME_LEN     = 12
+	FILENAME_PADDING = 4
+
+	chunkHeaderLen = 4 + 4 // magic number + 32 bit offset
+)
+
+type Section struct {
+	img      []byte
+	Magic    uint32
+	Offset   int
+	Length   int
+	Filename string
+}
+
+func FileSection(offset int, name string, contents []byte) *Section {
+	if len(name) > FILENAME_LEN {
+		panic(fmt.Sprintf("BUG: file name %s exceeds max FILENAME_LEN = %d", name, FILENAME_LEN))
+	}
+
+	img := bytes.Repeat([]byte{0}, offset+chunkHeaderLen)
+	img = append(img, []byte(name)...)
+	img = append(img, bytes.Repeat([]byte{0}, FILENAME_PADDING+FILENAME_LEN-len(name))...)
+	img = append(img, contents...)
+	return &Section{
+		img:      img,
+		Magic:    FILE_MAGIC,
+		Offset:   offset,
+		Length:   len(contents) + FILENAME_LEN + FILENAME_PADDING,
+		Filename: name,
+	}
+}
+
+func (s *Section) WithoutImg() Section {
+	without := *s
+	without.img = nil
+	return without
+}
+
+func (s *Section) RawContent() []byte {
+	offset := s.Offset + chunkHeaderLen
+	length := s.Length
+	return s.img[offset : offset+length]
+}
+
+func (s *Section) FileContent() []byte {
+	offset := s.Offset + chunkHeaderLen
+	length := s.Length
+	if s.Magic == FILE_MAGIC {
+		const fileSkip = FILENAME_LEN + FILENAME_PADDING
+		offset += fileSkip
+		length -= fileSkip
+	}
+	return s.img[offset : offset+length]
+}
+
+func Analyze(img []byte) ([]*Section, error) {
+	// See https://github.com/raspberrypi/rpi-eeprom/blob/f38dbcb72341a3c3c3e66f1e10d58f8985cb0528/rpi-eeprom-config#L267
+
+	if len(img) != 512*1024 &&
+		len(img) != 2*1024*1024 {
+		return nil, fmt.Errorf("unexpected EEPROM size: got %d, want 512KB or 2MB", len(img))
+	}
+
+	var sections []*Section
+	for offset := 0; offset+chunkHeaderLen < len(img); {
+		magic := binary.BigEndian.Uint32(img[offset : offset+4])
+		length := binary.BigEndian.Uint32(img[offset+4 : offset+8])
+		if magic == 0 || magic == 0xffffffff {
+			break // end of file
+		}
+		if magic&MAGIC_MASK != MAGIC {
+			return nil, fmt.Errorf("EEPROM is corrupted: %x & %x != %x", magic, MAGIC_MASK, MAGIC)
+		}
+		sect := Section{
+			img:    img,
+			Magic:  magic,
+			Offset: offset,
+			Length: int(length),
+		}
+		if magic == FILE_MAGIC {
+			sect.Filename = string(img[offset+8 : offset+8+FILENAME_LEN])
+			sect.Filename = strings.ReplaceAll(sect.Filename, "\x00", "")
+		}
+		sections = append(sections, &sect)
+		offset += chunkHeaderLen + int(length)
+		offset = (offset + 7) &^ 7
+	}
+	if len(sections) == 0 {
+		return nil, fmt.Errorf("invalid EEPROM: no sections found")
+	}
+	if sections[len(sections)-1].Filename != "bootconf.txt" {
+		// “by convention bootconf.txt is the last section”, from:
+		// https://github.com/raspberrypi/rpi-eeprom/blob/f38dbcb72341a3c3c3e66f1e10d58f8985cb0528/rpi-eeprom-config#L373
+		return nil, fmt.Errorf("invalid EEPROM: bootconf.txt not the last section")
+	}
+	return sections, nil
+}
+
+func Assemble(sections []*Section) []byte {
+	output := bytes.Repeat([]byte{0xff}, len(sections[0].img))
+	offset := 0
+	for _, sect := range sections {
+		binary.BigEndian.PutUint32(output[offset:], sect.Magic)
+		binary.BigEndian.PutUint32(output[offset+4:], uint32(sect.Length))
+		copy(output[offset+8:], sect.RawContent())
+		offset += chunkHeaderLen + sect.Length
+		offset = (offset + 7) &^ 7
+	}
+	return output
+}

internal/eeprom/eeprom_test.go

@@ -0,0 +1,110 @@
+package eeprom_test
+
+import (
+	"compress/gzip"
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/gokrazy/tools/internal/eeprom"
+)
+
+func testAgainst(t *testing.T, verify func(eepromPath, needle string), pieeprom, bootUartNeedle string) {
+	verify(pieeprom, bootUartNeedle)
+
+	// Read + Write the EEPROM with our own code,
+	// verify that bootconf.txt can still be displayed.
+	img, err := os.ReadFile(pieeprom)
+	if err != nil {
+		t.Fatal(err)
+	}
+	sections, err := eeprom.Analyze(img)
+	if err != nil {
+		t.Fatal(err)
+	}
+	reassembleAndVerify := func(needle string) {
+		reassembled := filepath.Join(t.TempDir(), "reassembled.bin")
+		if err := os.WriteFile(reassembled, eeprom.Assemble(sections), 0644); err != nil {
+			t.Fatal(err)
+		}
+		verify(reassembled, needle)
+	}
+	reassembleAndVerify(bootUartNeedle)
+
+	bc := sections[len(sections)-1] // guaranteed to be bootconf.txt
+
+	// Re-create the section with the existing contents.
+	sections[len(sections)-1] = eeprom.FileSection(bc.Offset, bc.Filename, bc.FileContent())
+	reassembleAndVerify(bootUartNeedle)
+
+	// Change the bootconf.txt contents.
+	sections[len(sections)-1] = eeprom.FileSection(bc.Offset, bc.Filename, []byte("hello world"))
+	reassembleAndVerify("hello world")
+}
+
+func TestAgainst(t *testing.T) {
+	const fn = "testdata/pieeprom-2025-10-17.bin"
+	f, err := os.Open(fn + ".gz")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+	gz, err := gzip.NewReader(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+	bin, err := io.ReadAll(gz)
+	if err != nil {
+		t.Fatal(err)
+	}
+	pieeprom := filepath.Join(t.TempDir(), filepath.Base(fn))
+	if err := os.WriteFile(pieeprom, bin, 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	t.Run("Infobeamer", func(t *testing.T) {
+		lsBin, err := exec.LookPath("pi-eeprom-ls")
+		if err != nil {
+			t.Skipf("pi-eeprom-ls not available (%v)", err)
+		}
+
+		verify := func(eepromPath, needle string) {
+			ls := exec.Command(lsBin, eepromPath)
+			ls.Stderr = os.Stderr
+			lsOut, err := ls.Output()
+			if err != nil {
+				t.Fatal(err)
+			}
+			if !strings.Contains(string(lsOut), needle) {
+				t.Errorf("infobeamer pi-eeprom-ls output did not contain %q: \n%s", needle, string(lsOut))
+			}
+		}
+		const bootUartNeedle = "-[ bootconf.txt ]------------------\n[all]\nBOOT_UART=1"
+		testAgainst(t, verify, pieeprom, bootUartNeedle)
+	})
+
+	t.Run("Pi", func(t *testing.T) {
+		configBin, err := exec.LookPath("rpi-eeprom-config")
+		if err != nil {
+			t.Skipf("rpi-eeprom-config not available (%v)", err)
+		}
+
+		verify := func(eepromPath, needle string) {
+			extract := exec.Command(configBin, eepromPath)
+			extract.Dir = t.TempDir()
+			extract.Stderr = os.Stderr
+			extractOut, err := extract.Output()
+			if err != nil {
+				t.Fatal(err)
+			}
+			if !strings.Contains(string(extractOut), needle) {
+				t.Errorf("rpi-eeprom-config output did not contain %q: \n%s", needle, string(extractOut))
+			}
+		}
+		const bootUartNeedle = "[all]\nBOOT_UART=1"
+		testAgainst(t, verify, pieeprom, bootUartNeedle)
+	})
+}

internal/gok/add.go

@@ -18,12 +18,13 @@ import (
 )
 
 // addCmd is gok add.
-var addCmd = &cobra.Command{
-	GroupID:               "edit",
-	Use:                   "add [flags] importpath[@version]",
-	DisableFlagsInUseLine: true,
-	Short:                 "Add a Go package to a gokrazy instance",
-	Long: `Add a Go package to a gokrazy instance.
+func addCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		GroupID:               "edit",
+		Use:                   "add [flags] importpath[@version]",
+		DisableFlagsInUseLine: true,
+		Short:                 "Add a Go package to a gokrazy instance",
+		Long: `Add a Go package to a gokrazy instance.
 
 This command creates the required build directory, runs go get, and adds
 the specified package to the gokrazy instance configuration (Packages field).
@@ -42,26 +43,25 @@ Examples:
   % gok -i scan2drive add /home/michael/projects/scanui/cmd/scanui
 
 `,
-	RunE: func(cmd *cobra.Command, args []string) error {
-		if cmd.Flags().NArg() != 1 {
-			fmt.Fprint(os.Stderr, `expected Go package name, name@version, or path
+		RunE: func(cmd *cobra.Command, args []string) error {
+			if cmd.Flags().NArg() != 1 {
+				fmt.Fprint(os.Stderr, `expected Go package name, name@version, or path
 
 `)
-			return cmd.Usage()
-		}
+				return cmd.Usage()
+			}
 
-		return addImpl.run(cmd.Context(), args[0], cmd.OutOrStdout(), cmd.OutOrStderr())
-	},
+			return addImpl.run(cmd.Context(), args[0], cmd.OutOrStdout(), cmd.OutOrStderr())
+		},
+	}
+	instanceflag.RegisterPflags(cmd.Flags())
+	return cmd
 }
 
 type addImplConfig struct{}
 
 var addImpl addImplConfig
 
-func init() {
-	instanceflag.RegisterPflags(addCmd.Flags())
-}
-
 type packageInfo struct {
 	// Dir is the directory on the local disk containing the package sources,
 	// e.g. /home/michael/projects/stapelberg/localmod/cmd/sup.

internal/gok/edit.go

@@ -13,32 +13,32 @@ import (
 )
 
 // editCmd is gok edit.
-var editCmd = &cobra.Command{
-	GroupID: "edit",
-	Use:     "edit",
-	Short:   "Edit a gokrazy instance configuration interactively",
-	Long: `Edit a gokrazy instance configuration interactively.
+func editCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		GroupID: "edit",
+		Use:     "edit",
+		Short:   "Edit a gokrazy instance configuration interactively",
+		Long: `Edit a gokrazy instance configuration interactively.
 `,
-	RunE: func(cmd *cobra.Command, args []string) error {
-		if cmd.Flags().NArg() > 0 {
-			fmt.Fprint(os.Stderr, `positional arguments are not supported
+		RunE: func(cmd *cobra.Command, args []string) error {
+			if cmd.Flags().NArg() > 0 {
+				fmt.Fprint(os.Stderr, `positional arguments are not supported
 
 `)
-			return cmd.Usage()
-		}
+				return cmd.Usage()
+			}
 
-		return editImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
-	},
+			return editImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
+		},
+	}
+	instanceflag.RegisterPflags(cmd.Flags())
+	return cmd
 }
 
 type editImplConfig struct{}
 
 var editImpl editImplConfig
 
-func init() {
-	instanceflag.RegisterPflags(editCmd.Flags())
-}
-
 func (r *editImplConfig) run(ctx context.Context, args []string, stdout, stderr io.Writer) error {
 	parentDir := instanceflag.ParentDir()
 	instance := instanceflag.Instance()

internal/gok/get.go

@@ -11,17 +11,17 @@ import (
 
 	"github.com/gokrazy/internal/config"
 	"github.com/gokrazy/internal/instanceflag"
-	"github.com/gokrazy/internal/updateflag"
 	"github.com/gokrazy/tools/packer"
 	"github.com/spf13/cobra"
 )
 
 // getCmd is gok get.
-var getCmd = &cobra.Command{
-	GroupID: "edit",
-	Use:     "get",
-	Short:   "Update the version of your Go program(s) using `go get`",
-	Long: "gok get runs `go get` to update the version of the specified Go programs" + `
+func getCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		GroupID: "edit",
+		Use:     "get",
+		Short:   "Update the version of your Go program(s) using `go get`",
+		Long: "gok get runs `go get` to update the version of the specified Go programs" + `
 in your gokrazy instance.
 
 Examples:
@@ -34,9 +34,13 @@ Examples:
   # Update only gokrazy system packages
   % gok -i scanner get gokrazy
 `,
-	RunE: func(cmd *cobra.Command, args []string) error {
-		return getImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
-	},
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return getImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
+		},
+	}
+	cmd.Flags().BoolVarP(&getImpl.updateAll, "update_all", "u", false, "update all installed packages and gokrazy system packages")
+	instanceflag.RegisterPflags(cmd.Flags())
+	return cmd
 }
 
 type getImplConfig struct {
@@ -45,11 +49,6 @@ type getImplConfig struct {
 
 var getImpl getImplConfig
 
-func init() {
-	getCmd.Flags().BoolVarP(&getImpl.updateAll, "update_all", "u", false, "update all installed packages and gokrazy system packages")
-	instanceflag.RegisterPflags(getCmd.Flags())
-}
-
 func getGokrazySystemPackages(cfg *config.Struct) []string {
 	pkgs := append([]string{}, cfg.GokrazyPackagesOrDefault()...)
 	pkgs = append(pkgs, packer.InitDeps(cfg.InternalCompatibilityFlags.InitPkg)...)
@@ -78,8 +77,6 @@ func (r *getImplConfig) run(ctx context.Context, args []string, stdout, stderr i
 		return err
 	}
 
-	updateflag.SetUpdate("yes")
-
 	packages := args
 	if r.updateAll {
 		if len(packages) > 0 {

internal/gok/logs.go

@@ -20,15 +20,20 @@ import (
 )
 
 // logsCmd is gok logs.
-var logsCmd = &cobra.Command{
-	GroupID: "runtime",
-	Use:     "logs",
-	Short:   "Stream logs from a running gokrazy service",
-	Long: `Display the most recent 100 log lines from stdout and stderr each,
+func logsCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		GroupID: "runtime",
+		Use:     "logs",
+		Short:   "Stream logs from a running gokrazy service",
+		Long: `Display the most recent 100 log lines from stdout and stderr each,
 and any new lines the gokrazy service produces (cancel any time with Ctrl-C)`,
-	RunE: func(cmd *cobra.Command, args []string) error {
-		return logsImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
-	},
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return logsImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
+		},
+	}
+	cmd.Flags().StringVarP(&logsImpl.service, "service", "s", "", "gokrazy service to fetch logs for")
+	instanceflag.RegisterPflags(cmd.Flags())
+	return cmd
 }
 
 type logsImplConfig struct {
@@ -37,11 +42,6 @@ type logsImplConfig struct {
 
 var logsImpl logsImplConfig
 
-func init() {
-	logsCmd.Flags().StringVarP(&logsImpl.service, "service", "s", "", "gokrazy service to fetch logs for")
-	instanceflag.RegisterPflags(logsCmd.Flags())
-}
-
 func (l *logsImplConfig) run(ctx context.Context, args []string, stdout, stderr io.Writer) error {
 	cfg, err := config.ApplyInstanceFlag()
 	if err != nil {
@@ -53,13 +53,11 @@ func (l *logsImplConfig) run(ctx context.Context, args []string, stdout, stderr
 		}
 	}
 
-	updateflag.SetUpdate("yes")
-
 	if l.service == "" {
 		return fmt.Errorf("the -service flag is empty, but required")
 	}
 
-	httpClient, _, logsUrl, err := httpclient.For(cfg)
+	httpClient, _, logsUrl, err := httpclient.For(updateflag.Value{Update: "yes"}, cfg)
 	if err != nil {
 		return err
 	}

internal/gok/new.go

@@ -16,25 +16,30 @@ import (
 )
 
 // newCmd is gok new.
-var newCmd = &cobra.Command{
-	GroupID: "edit",
-	Use:     "new",
-	Short:   "Create a new gokrazy instance",
-	Long: `Create a new gokrazy instance.
+func newCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		GroupID: "edit",
+		Use:     "new",
+		Short:   "Create a new gokrazy instance",
+		Long: `Create a new gokrazy instance.
 
 If you are unfamiliar with gokrazy, please follow:
 https://gokrazy.org/quickstart/
 `,
-	RunE: func(cmd *cobra.Command, args []string) error {
-		if cmd.Flags().NArg() > 0 {
-			fmt.Fprint(os.Stderr, `positional arguments are not supported
+		RunE: func(cmd *cobra.Command, args []string) error {
+			if cmd.Flags().NArg() > 0 {
+				fmt.Fprint(os.Stderr, `positional arguments are not supported
 
 `)
-			return cmd.Usage()
-		}
+				return cmd.Usage()
+			}
 
-		return newImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
-	},
+			return newImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
+		},
+	}
+	instanceflag.RegisterPflags(cmd.Flags())
+	cmd.Flags().BoolVarP(&newImpl.empty, "empty", "", false, "create an empty gokrazy instance, without the default packages")
+	return cmd
 }
 
 type newImplConfig struct {
@@ -43,11 +48,6 @@ type newImplConfig struct {
 
 var newImpl newImplConfig
 
-func init() {
-	instanceflag.RegisterPflags(newCmd.Flags())
-	newCmd.Flags().BoolVarP(&newImpl.empty, "empty", "", false, "create an empty gokrazy instance, without the default packages")
-}
-
 func (r *newImplConfig) createBreakglassAuthorizedKeys(authorizedPath string, matches []string) error {
 	f, err := os.OpenFile(authorizedPath, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0600)
 	if err != nil {

internal/gok/overwrite.go

@@ -15,11 +15,12 @@ import (
 )
 
 // overwriteCmd is gok overwrite.
-var overwriteCmd = &cobra.Command{
-	GroupID: "deploy",
-	Use:     "overwrite",
-	Short:   "Build and deploy a gokrazy instance to a storage device",
-	Long: `Build and deploy a gokrazy instance to a storage device.
+func overwriteCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		GroupID: "deploy",
+		Use:     "overwrite",
+		Short:   "Build and deploy a gokrazy instance to a storage device",
+		Long: `Build and deploy a gokrazy instance to a storage device.
 
 You typically need to use the gok overwrite command only once,
 when first deploying your gokrazy instance. Afterwards, you can
@@ -29,16 +30,27 @@ Examples:
   # Overwrite the contents of the SD card sdx with gokrazy instance scan2drive:
   % gok -i scan2drive overwrite --full=/dev/sdx
 `,
-	RunE: func(cmd *cobra.Command, args []string) error {
-		if cmd.Flags().NArg() > 0 {
-			fmt.Fprint(os.Stderr, `positional arguments are not supported
+		RunE: func(cmd *cobra.Command, args []string) error {
+			if cmd.Flags().NArg() > 0 {
+				fmt.Fprint(os.Stderr, `positional arguments are not supported
 
 `)
-			return cmd.Usage()
-		}
+				return cmd.Usage()
+			}
 
-		return overwriteImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
-	},
+			return overwriteImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
+		},
+	}
+	instanceflag.RegisterPflags(cmd.Flags())
+	cmd.Flags().StringVarP(&overwriteImpl.full, "full", "", "", "write a full gokrazy device image to the specified device (e.g. /dev/sdx) or path (e.g. /tmp/gokrazy.img)")
+	cmd.Flags().StringVarP(&overwriteImpl.gaf, "gaf", "", "", "write a .gaf (gokrazy archive format) file to the specified path (e.g. /tmp/gokrazy.gaf)")
+	cmd.Flags().StringVarP(&overwriteImpl.boot, "boot", "", "", "write the gokrazy boot file system to the specified partition (e.g. /dev/sdx1) or path (e.g. /tmp/boot.fat)")
+	cmd.Flags().StringVarP(&overwriteImpl.root, "root", "", "", "write the gokrazy root file system to the specified partition (e.g. /dev/sdx2) or path (e.g. /tmp/root.squashfs)")
+	cmd.Flags().StringVarP(&overwriteImpl.mbr, "mbr", "", "", "write the gokrazy master boot record (MBR) to the specified device (e.g. /dev/sdx) or path (e.g. /tmp/mbr.img). only effective if -boot is specified, too")
+	cmd.Flags().StringVarP(&overwriteImpl.sudo, "sudo", "", "", "Whether to elevate privileges using sudo when required (one of auto, always, never, default auto)")
+	cmd.Flags().IntVarP(&overwriteImpl.targetStorageBytes, "target_storage_bytes", "", 0, "Number of bytes which the target storage device (SD card) has. Required for using -full=<file>")
+	cmd.Flags().StringVarP(&overwriteImpl.traceFile, "trace_file", "", "", "If non-empty, write a Go runtime/trace to this file (for performance analysis)")
+	return cmd
 }
 
 type overwriteImplConfig struct {
@@ -56,18 +68,6 @@ type overwriteImplConfig struct {
 
 var overwriteImpl overwriteImplConfig
 
-func init() {
-	instanceflag.RegisterPflags(overwriteCmd.Flags())
-	overwriteCmd.Flags().StringVarP(&overwriteImpl.full, "full", "", "", "write a full gokrazy device image to the specified device (e.g. /dev/sdx) or path (e.g. /tmp/gokrazy.img)")
-	overwriteCmd.Flags().StringVarP(&overwriteImpl.gaf, "gaf", "", "", "write a .gaf (gokrazy archive format) file to the specified path (e.g. /tmp/gokrazy.gaf)")
-	overwriteCmd.Flags().StringVarP(&overwriteImpl.boot, "boot", "", "", "write the gokrazy boot file system to the specified partition (e.g. /dev/sdx1) or path (e.g. /tmp/boot.fat)")
-	overwriteCmd.Flags().StringVarP(&overwriteImpl.root, "root", "", "", "write the gokrazy root file system to the specified partition (e.g. /dev/sdx2) or path (e.g. /tmp/root.squashfs)")
-	overwriteCmd.Flags().StringVarP(&overwriteImpl.mbr, "mbr", "", "", "write the gokrazy master boot record (MBR) to the specified device (e.g. /dev/sdx) or path (e.g. /tmp/mbr.img). only effective if -boot is specified, too")
-	overwriteCmd.Flags().StringVarP(&overwriteImpl.sudo, "sudo", "", "", "Whether to elevate privileges using sudo when required (one of auto, always, never, default auto)")
-	overwriteCmd.Flags().IntVarP(&overwriteImpl.targetStorageBytes, "target_storage_bytes", "", 0, "Number of bytes which the target storage device (SD card) has. Required for using -full=<file>")
-	overwriteCmd.Flags().StringVarP(&overwriteImpl.traceFile, "trace_file", "", "", "If non-empty, write a Go runtime/trace to this file (for performance analysis)")
-}
-
 func (r *overwriteImplConfig) run(ctx context.Context, args []string, stdout, stderr io.Writer) error {
 	if r.traceFile != "" {
 		out, err := os.Create(r.traceFile)
@@ -151,7 +151,7 @@ func (r *overwriteImplConfig) run(ctx context.Context, args []string, stdout, st
 		Output:  &output,
 	}
 
-	pack.Main(ctx, "gokrazy gok")
+	pack.Main(ctx)
 
 	return nil
 }

internal/gok/ps.go

@@ -14,18 +14,22 @@ import (
 )
 
 // psCmd is gok ps.
-var psCmd = &cobra.Command{
-	GroupID: "runtime",
-	Use:     "ps",
-	Short:   "list processes of a running gokrazy instance",
-	Long: `gok ps
+func psCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		GroupID: "runtime",
+		Use:     "ps",
+		Short:   "list processes of a running gokrazy instance",
+		Long: `gok ps
 
 Examples:
   % gok -i scan2drive ps
   `,
-	RunE: func(cmd *cobra.Command, args []string) error {
-		return psImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
-	},
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return psImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
+		},
+	}
+	instanceflag.RegisterPflags(cmd.Flags())
+	return cmd
 }
 
 type psImplConfig struct {
@@ -33,10 +37,6 @@ type psImplConfig struct {
 
 var psImpl psImplConfig
 
-func init() {
-	instanceflag.RegisterPflags(psCmd.Flags())
-}
-
 func (r *psImplConfig) run(ctx context.Context, args []string, stdout, stderr io.Writer) error {
 	cfg, err := config.ApplyInstanceFlag()
 	if err != nil {

internal/gok/push.go

@@ -15,11 +15,12 @@ import (
 )
 
 // pushCmd is gok push.
-var pushCmd = &cobra.Command{
-	GroupID: "server",
-	Use:     "push",
-	Short:   "Push a gokrazy image to a remote GUS server",
-	Long: `gok push pushes a local gaf (gokrazy archive format) file to a remote server.
+func pushCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		GroupID: "server",
+		Use:     "push",
+		Short:   "Push a gokrazy image to a remote GUS server",
+		Long: `gok push pushes a local gaf (gokrazy archive format) file to a remote server.
 
 When the --json flag is specified, the server response is printed to stdout.
 
@@ -28,9 +29,15 @@ Examples:
   % gok push --gaf /tmp/gokrazy.gaf --server https://gus.gokrazy.org
 
 `,
-	RunE: func(cmd *cobra.Command, args []string) error {
-		return pushImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
-	},
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return pushImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
+		},
+	}
+	cmd.Flags().StringVarP(&pushImpl.gafPath, "gaf", "", "", "path to the .gaf (gokrazy archive format) file to push to GUS (e.g. /tmp/gokrazy.gaf); build using gok overwrite --gaf")
+	cmd.Flags().StringVarP(&pushImpl.server, "server", "", "", "HTTP(S) URL to the server to push to")
+	cmd.Flags().BoolVarP(&pushImpl.json, "json", "", false, "print server JSON response directly to stdout")
+	instanceflag.RegisterPflags(cmd.Flags())
+	return cmd
 }
 
 type pushConfig struct {
@@ -41,13 +48,6 @@ type pushConfig struct {
 
 var pushImpl pushConfig
 
-func init() {
-	pushCmd.Flags().StringVarP(&pushImpl.gafPath, "gaf", "", "", "path to the .gaf (gokrazy archive format) file to push to GUS (e.g. /tmp/gokrazy.gaf); build using gok overwrite --gaf")
-	pushCmd.Flags().StringVarP(&pushImpl.server, "server", "", "", "HTTP(S) URL to the server to push to")
-	pushCmd.Flags().BoolVarP(&pushImpl.json, "json", "", false, "print server JSON response directly to stdout")
-	instanceflag.RegisterPflags(pushCmd.Flags())
-}
-
 func (r *pushConfig) run(ctx context.Context, args []string, stdout, stderr io.Writer) error {
 	// TODO: use an io.Reader that allows us to indicate progress
 	body, err := os.Open(r.gafPath)

internal/gok/root.go

@@ -9,10 +9,11 @@ import (
 	"github.com/spf13/pflag"
 )
 
-var RootCmd = &cobra.Command{
-	Use:   "gok",
-	Short: "top-level CLI entry point for all things gokrazy",
-	Long: `The gok tool is your main entrypoint to gokrazy and allows you to:
+func RootCmd() *cobra.Command {
+	rootCmd := &cobra.Command{
+		Use:   "gok",
+		Short: "top-level CLI entry point for all things gokrazy",
+		Long: `The gok tool is your main entrypoint to gokrazy and allows you to:
 
 1. Create new gokrazy instances (gok new),
 2. Deploy gokrazy instances to storage devices like SD cards (gok overwrite),
@@ -22,59 +23,58 @@ var RootCmd = &cobra.Command{
 If you are unfamiliar with gokrazy, please follow:
 https://gokrazy.org/quickstart/
 `,
-	SilenceErrors: true,
-	SilenceUsage:  true,
-	RunE: func(cmd *cobra.Command, args []string) error {
-		versionVal, err := cmd.Flags().GetBool("version")
-		if err != nil {
-			return fmt.Errorf("BUG: version flag declared as non-bool")
-		}
-		if versionVal {
-			fmt.Println(version.Read())
-			return nil
-		}
-		return pflag.ErrHelp
-	},
-}
-
-func init() {
-	RootCmd.AddGroup(&cobra.Group{
+		SilenceErrors: true,
+		SilenceUsage:  true,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			versionVal, err := cmd.Flags().GetBool("version")
+			if err != nil {
+				return fmt.Errorf("BUG: version flag declared as non-bool")
+			}
+			if versionVal {
+				fmt.Println(version.Read())
+				return nil
+			}
+			return pflag.ErrHelp
+		},
+	}
+	rootCmd.AddGroup(&cobra.Group{
 		ID:    "edit",
 		Title: "Commands to create and edit a gokrazy instance:",
 	})
-	RootCmd.AddGroup(&cobra.Group{
+	rootCmd.AddGroup(&cobra.Group{
 		ID:    "deploy",
 		Title: "Commands to deploy and update a gokrazy instance:",
 	})
-	RootCmd.AddGroup(&cobra.Group{
+	rootCmd.AddGroup(&cobra.Group{
 		ID:    "runtime",
 		Title: "Commands to work with a running gokrazy instance:",
 	})
-	RootCmd.AddGroup(&cobra.Group{
+	rootCmd.AddGroup(&cobra.Group{
 		ID:    "server",
 		Title: "Commands to work with a remote GUS server:",
 	})
-	RootCmd.AddGroup(&cobra.Group{
+	rootCmd.AddGroup(&cobra.Group{
 		ID:    "vm",
 		Title: "Commands to work with Virtual Machines (VMs):",
 	})
-	RootCmd.Flags().Bool("version", false, "print gok version")
+	rootCmd.Flags().Bool("version", false, "print gok version")
 	// Only defined so that it appears in documentation like --help.
 	//
 	// Cobra only parses local flags on the target command, but they can appear
 	// at any place in the command line (before or after the verb).
-	instanceflag.RegisterPflags(RootCmd.Flags())
-	RootCmd.AddCommand(runCmd)
-	RootCmd.AddCommand(logsCmd)
-	RootCmd.AddCommand(updateCmd)
-	RootCmd.AddCommand(overwriteCmd)
-	RootCmd.AddCommand(versionCmd)
-	RootCmd.AddCommand(newCmd)
-	RootCmd.AddCommand(editCmd)
-	RootCmd.AddCommand(addCmd)
-	RootCmd.AddCommand(getCmd)
-	RootCmd.AddCommand(sbomCmd)
-	RootCmd.AddCommand(pushCmd)
-	RootCmd.AddCommand(vmCmd)
-	RootCmd.AddCommand(psCmd)
+	instanceflag.RegisterPflags(rootCmd.Flags())
+	rootCmd.AddCommand(runCmd())
+	rootCmd.AddCommand(logsCmd())
+	rootCmd.AddCommand(updateCmd())
+	rootCmd.AddCommand(overwriteCmd())
+	rootCmd.AddCommand(versionCmd())
+	rootCmd.AddCommand(newCmd())
+	rootCmd.AddCommand(editCmd())
+	rootCmd.AddCommand(addCmd())
+	rootCmd.AddCommand(getCmd())
+	rootCmd.AddCommand(sbomCmd())
+	rootCmd.AddCommand(pushCmd())
+	rootCmd.AddCommand(vmCmd())
+	rootCmd.AddCommand(psCmd())
+	return rootCmd
 }

internal/gok/run.go

@@ -22,11 +22,12 @@ import (
 )
 
 // runCmd is gok run.
-var runCmd = &cobra.Command{
-	GroupID: "runtime",
-	Use:     "run",
-	Short:   "`go install` and run on a running gokrazy instance",
-	Long: "gok run uses `go install` to build the Go program in the current directory," + `
+func runCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		GroupID: "runtime",
+		Use:     "run",
+		Short:   "`go install` and run on a running gokrazy instance",
+		Long: "gok run uses `go install` to build the Go program in the current directory," + `
 then it stores the program in RAM of a running gokrazy instance and runs the program.
 
 This enables a quick feedback loop when working on a program that is running on gokrazy,
@@ -42,9 +43,13 @@ Examples:
   # specify extra flags on the command line
   % gok -i scan2drive run -- -tls_autocert_hosts=scan.example.com
   `,
-	RunE: func(cmd *cobra.Command, args []string) error {
-		return runImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
-	},
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return runImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
+		},
+	}
+	cmd.Flags().BoolVarP(&runImpl.keep, "keep", "k", false, "keep temporary binary")
+	instanceflag.RegisterPflags(cmd.Flags())
+	return cmd
 }
 
 type runImplConfig struct {
@@ -53,11 +58,6 @@ type runImplConfig struct {
 
 var runImpl runImplConfig
 
-func init() {
-	runCmd.Flags().BoolVarP(&runImpl.keep, "keep", "k", false, "keep temporary binary")
-	instanceflag.RegisterPflags(runCmd.Flags())
-}
-
 func (r *runImplConfig) run(ctx context.Context, args []string, stdout, stderr io.Writer) error {
 	cfg, err := config.ApplyInstanceFlag()
 	if err != nil {
@@ -69,8 +69,6 @@ func (r *runImplConfig) run(ctx context.Context, args []string, stdout, stderr i
 		}
 	}
 
-	updateflag.SetUpdate("yes")
-
 	var tmp string
 	if r.keep {
 		tmp = os.TempDir()
@@ -122,7 +120,7 @@ func (r *runImplConfig) run(ctx context.Context, args []string, stdout, stderr i
 		return err
 	}
 
-	httpClient, _, updateBaseUrl, err := httpclient.For(cfg)
+	httpClient, _, updateBaseUrl, err := httpclient.For(updateflag.Value{Update: "yes"}, cfg)
 	if err != nil {
 		return err
 	}

internal/gok/sbom.go

@@ -10,17 +10,17 @@ import (
 
 	"github.com/gokrazy/internal/config"
 	"github.com/gokrazy/internal/instanceflag"
-	"github.com/gokrazy/internal/updateflag"
 	"github.com/gokrazy/tools/internal/packer"
 	"github.com/spf13/cobra"
 )
 
 // sbomCmd is gok sbom.
-var sbomCmd = &cobra.Command{
-	GroupID: "deploy",
-	Use:     "sbom",
-	Short:   "Print the Software Bill Of Materials of a gokrazy instance",
-	Long: `gok sbom generates an SBOM of what gok overwrite or gok update would build
+func sbomCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		GroupID: "deploy",
+		Use:     "sbom",
+		Short:   "Print the Software Bill Of Materials of a gokrazy instance",
+		Long: `gok sbom generates an SBOM of what gok overwrite or gok update would build
 
 Examples:
   # print the hash and SBOM contents in JSON format
@@ -30,9 +30,13 @@ Examples:
   % gok -i scanner sbom --format hash
 
 `,
-	RunE: func(cmd *cobra.Command, args []string) error {
-		return sbomImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
-	},
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return sbomImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
+		},
+	}
+	cmd.Flags().StringVarP(&sbomImpl.format, "format", "", "json", "output format. one of json or hash")
+	instanceflag.RegisterPflags(cmd.Flags())
+	return cmd
 }
 
 type sbomConfig struct {
@@ -41,11 +45,6 @@ type sbomConfig struct {
 
 var sbomImpl sbomConfig
 
-func init() {
-	sbomCmd.Flags().StringVarP(&sbomImpl.format, "format", "", "json", "output format. one of json or hash")
-	instanceflag.RegisterPflags(sbomCmd.Flags())
-}
-
 func (r *sbomConfig) run(ctx context.Context, args []string, stdout, stderr io.Writer) error {
 	fileCfg, err := config.ApplyInstanceFlag()
 	if err != nil {
@@ -66,8 +65,6 @@ func (r *sbomConfig) run(ctx context.Context, args []string, stdout, stderr io.W
 		return err
 	}
 
-	updateflag.SetUpdate("yes")
-
 	var buf bytes.Buffer
 	pack := &packer.Pack{
 		// Send all build output to stderr so that stdout

internal/gok/update.go

@@ -13,22 +13,28 @@ import (
 )
 
 // updateCmd is gok update.
-var updateCmd = &cobra.Command{
-	GroupID: "deploy",
-	Use:     "update",
-	Short:   "Build a gokrazy instance and update over the network",
-	Long: `Build a gokrazy instance and update over the network.
+func updateCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		GroupID: "deploy",
+		Use:     "update",
+		Short:   "Build a gokrazy instance and update over the network",
+		Long: `Build a gokrazy instance and update over the network.
 `,
-	RunE: func(cmd *cobra.Command, args []string) error {
-		if cmd.Flags().NArg() > 0 {
-			fmt.Fprint(os.Stderr, `positional arguments are not supported
+		RunE: func(cmd *cobra.Command, args []string) error {
+			if cmd.Flags().NArg() > 0 {
+				fmt.Fprint(os.Stderr, `positional arguments are not supported
 
 `)
-			return cmd.Usage()
-		}
+				return cmd.Usage()
+			}
 
-		return updateImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
-	},
+			return updateImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
+		},
+	}
+	instanceflag.RegisterPflags(cmd.Flags())
+	cmd.Flags().BoolVarP(&updateImpl.insecure, "insecure", "", false, "Disable TLS stripping detection. Should only be used when first enabling TLS, not permanently.")
+	cmd.Flags().BoolVarP(&updateImpl.testboot, "testboot", "", false, "Trigger a testboot instead of switching to the new root partition directly")
+	return cmd
 }
 
 type updateImplConfig struct {
@@ -38,12 +44,6 @@ type updateImplConfig struct {
 
 var updateImpl updateImplConfig
 
-func init() {
-	instanceflag.RegisterPflags(updateCmd.Flags())
-	updateCmd.Flags().BoolVarP(&updateImpl.insecure, "insecure", "", false, "Disable TLS stripping detection. Should only be used when first enabling TLS, not permanently.")
-	updateCmd.Flags().BoolVarP(&updateImpl.testboot, "testboot", "", false, "Trigger a testboot instead of switching to the new root partition directly")
-}
-
 func (r *updateImplConfig) run(ctx context.Context, args []string, stdout, stderr io.Writer) error {
 	fileCfg, err := config.ApplyInstanceFlag()
 	if err != nil {
@@ -90,7 +90,7 @@ func (r *updateImplConfig) run(ctx context.Context, args []string, stdout, stder
 		Cfg:     cfg,
 	}
 
-	pack.Main(ctx, "gokrazy gok")
+	pack.Main(ctx)
 
 	return nil
 }

internal/gok/version.go

@@ -10,13 +10,16 @@ import (
 )
 
 // versionCmd is gok version.
-var versionCmd = &cobra.Command{
-	Use:   "version",
-	Short: "Print gok version",
-	Long:  `Print gok version`,
-	RunE: func(cmd *cobra.Command, args []string) error {
-		return versionImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
-	},
+func versionCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "version",
+		Short: "Print gok version",
+		Long:  `Print gok version`,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return versionImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
+		},
+	}
+	return cmd
 }
 
 type versionImplConfig struct{}

internal/gok/vm.go

@@ -5,11 +5,15 @@ import (
 )
 
 // vmCmd is the gok vm subcommand, which (only) has nested commands like run.
-var vmCmd = &cobra.Command{
-	GroupID: "vm",
-	Use:     "vm",
-	Short:   "virtual machine",
-	RunE: func(cmd *cobra.Command, args []string) error {
-		return cmd.Usage()
-	},
+func vmCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		GroupID: "vm",
+		Use:     "vm",
+		Short:   "virtual machine",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return cmd.Usage()
+		},
+	}
+	cmd.AddCommand(vmRunCmd())
+	return cmd
 }

internal/gok/vmrun.go

@@ -18,10 +18,11 @@ import (
 	"github.com/spf13/cobra"
 )
 
-var vmRunCmd = &cobra.Command{
-	Use:   "run",
-	Short: "run a virtual machine (using QEMU)",
-	Long: `gok run builds a gokrazy instance and runs it using QEMU.
+func vmRunCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "run",
+		Short: "run a virtual machine (using QEMU)",
+		Long: `gok run builds a gokrazy instance and runs it using QEMU.
 
 Extra arguments are passed to QEMU as-is.
 
@@ -35,13 +36,20 @@ Examples:
   # Directly specify QEMU USB flags
   % gok vm run -- -usb -device usb-mouse
 `,
-	RunE: func(cmd *cobra.Command, args []string) error {
-		return vmRunImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
-	},
-}
-
-func init() {
-	vmCmd.AddCommand(vmRunCmd)
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return vmRunImpl.run(cmd.Context(), args, cmd.OutOrStdout(), cmd.OutOrStderr())
+		},
+	}
+	cmd.Flags().StringVarP(&vmRunImpl.sudo, "sudo", "", "", "Whether to elevate privileges using sudo when required (one of auto, always, never, default auto)")
+	const permSize = 512 * 1024 * 1024
+	cmd.Flags().IntVarP(&vmRunImpl.targetStorageBytes, "target_storage_bytes", "", 1258299392+permSize, "Size of the disk image in bytes")
+	cmd.Flags().StringVarP(&vmRunImpl.arch, "arch", "", "", "architecture for which to build and run QEMU. One of 'amd64' or 'arm64'")
+	cmd.Flags().StringVarP(&vmRunImpl.netdev, "netdev", "", "user,id=net0,hostfwd=tcp::8080-:80,hostfwd=tcp::8022-:22", "QEMU -netdev argument")
+	cmd.Flags().BoolVarP(&vmRunImpl.keep, "keep", "", false, "keep ephemeral disk images around instead of deleting them when QEMU exits")
+	cmd.Flags().BoolVarP(&vmRunImpl.dry, "dryrun", "", false, "Whether to actually run QEMU or merely print the command")
+	cmd.Flags().BoolVarP(&vmRunImpl.graphic, "graphic", "", true, "Run QEMU in graphical mode?")
+	instanceflag.RegisterPflags(cmd.Flags())
+	return cmd
 }
 
 type vmRunConfig struct {
@@ -64,18 +72,6 @@ func (r *vmRunConfig) effectiveGoarch() string {
 
 var vmRunImpl vmRunConfig
 
-func init() {
-	vmRunCmd.Flags().StringVarP(&vmRunImpl.sudo, "sudo", "", "", "Whether to elevate privileges using sudo when required (one of auto, always, never, default auto)")
-	const permSize = 512 * 1024 * 1024
-	vmRunCmd.Flags().IntVarP(&vmRunImpl.targetStorageBytes, "target_storage_bytes", "", 1258299392+permSize, "Size of the disk image in bytes")
-	vmRunCmd.Flags().StringVarP(&vmRunImpl.arch, "arch", "", "", "architecture for which to build and run QEMU. One of 'amd64' or 'arm64'")
-	vmRunCmd.Flags().StringVarP(&vmRunImpl.netdev, "netdev", "", "user,id=net0,hostfwd=tcp::8080-:80,hostfwd=tcp::8022-:22", "QEMU -netdev argument")
-	vmRunCmd.Flags().BoolVarP(&vmRunImpl.keep, "keep", "", false, "keep ephemeral disk images around instead of deleting them when QEMU exits")
-	vmRunCmd.Flags().BoolVarP(&vmRunImpl.dry, "dryrun", "", false, "Whether to actually run QEMU or merely print the command")
-	vmRunCmd.Flags().BoolVarP(&vmRunImpl.graphic, "graphic", "", true, "Run QEMU in graphical mode?")
-	instanceflag.RegisterPflags(vmRunCmd.Flags())
-}
-
 func (r *vmRunConfig) buildFullDiskImage(ctx context.Context, dest string, fileCfg *config.Struct) error {
 
 	if r.arch != "" {
@@ -133,7 +129,7 @@ func (r *vmRunConfig) buildFullDiskImage(ctx context.Context, dest string, fileC
 		Output:  &output,
 	}
 
-	pack.Main(ctx, "gokrazy gok")
+	pack.Main(ctx)
 
 	return nil
 }

internal/packer/certs.go

@@ -93,7 +93,7 @@ func generateAndStoreSelfSignedCertificate(cfg *config.Struct, hostConfigPath, c
 }
 
 func getCertificate(cfg *config.Struct) (string, string, error) {
-	certPath, keyPath, err := tlsflag.CertificatePathsFor(cfg.Hostname)
+	certPath, keyPath, err := tlsflag.CertificatePathsFor(cfg.Update.UseTLS, cfg.Hostname)
 	if err != nil {
 		var nycerr *tlsflag.ErrNotYetCreated
 		if errors.As(err, &nycerr) {

internal/packer/eeprom.go

@@ -0,0 +1,56 @@
+package packer
+
+import (
+	"io"
+	"os"
+	"strings"
+
+	"github.com/gokrazy/tools/internal/eeprom"
+)
+
+func applyExtraEEPROM(pieeprom string, extraEEPROM []string) ([]byte, error) {
+	upstream, err := os.Open(pieeprom)
+	if err != nil {
+		return nil, err
+	}
+	upstreamBin, err := io.ReadAll(upstream)
+	if err != nil {
+		return nil, err
+	}
+	sections, err := eeprom.Analyze(upstreamBin)
+	if err != nil {
+		return nil, err
+	}
+	bc := sections[len(sections)-1] // guaranteed to be bootconf.txt
+	bootconfTxt := bc.FileContent()
+	applied := overwriteBootconf(bootconfTxt, extraEEPROM)
+	sections[len(sections)-1] = eeprom.FileSection(bc.Offset, bc.Filename, applied)
+	return eeprom.Assemble(sections), nil
+}
+
+func overwriteBootconf(bootconfTxt []byte, extraEEPROM []string) []byte {
+	bootconfLines := strings.Split(strings.TrimSpace(string(bootconfTxt)), "\n")
+	// For each property, there will be an entry from property to full line
+	extraByProp := make(map[string]string)
+	for _, line := range extraEEPROM {
+		prop, _, ok := strings.Cut(line, "=")
+		if !ok {
+			continue
+		}
+		extraByProp[prop] = line
+	}
+	var out strings.Builder
+	for _, line := range bootconfLines {
+		prop, _, ok := strings.Cut(line, "=")
+		if !ok {
+			out.WriteString(line + "\n")
+			continue
+		}
+		if extra, ok := extraByProp[prop]; ok {
+			out.WriteString(extra + "\n")
+		} else {
+			out.WriteString(line + "\n")
+		}
+	}
+	return []byte(out.String())
+}

internal/packer/packerbuild.go

@@ -0,0 +1,398 @@
+package packer
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime/trace"
+	"strings"
+	"time"
+
+	"github.com/gokrazy/internal/updateflag"
+	"github.com/gokrazy/tools/packer"
+)
+
+func (pack *Pack) logicBuild(bindir string) error {
+	log := pack.Env.Logger()
+
+	cfg := pack.Cfg // for convenience
+	args := cfg.Packages
+	log.Printf("Building %d Go packages:", len(args))
+	log.Printf("")
+	for _, pkg := range args {
+		log.Printf("  %s", pkg)
+		for _, configFile := range packageConfigFiles[pkg] {
+			log.Printf("    will %s",
+				configFile.kind)
+			if configFile.path != "" {
+				log.Printf("      from %s",
+					configFile.path)
+			}
+			if !configFile.lastModified.IsZero() {
+				log.Printf("      last modified: %s (%s ago)",
+					configFile.lastModified.Format(time.RFC3339),
+					time.Since(configFile.lastModified).Round(1*time.Second))
+			}
+		}
+		log.Printf("")
+	}
+
+	pkgs := append([]string{}, cfg.GokrazyPackagesOrDefault()...)
+	pkgs = append(pkgs, cfg.Packages...)
+	pkgs = append(pkgs, packer.InitDeps(cfg.InternalCompatibilityFlags.InitPkg)...)
+	noBuildPkgs := []string{
+		cfg.KernelPackageOrDefault(),
+	}
+	if fw := cfg.FirmwarePackageOrDefault(); fw != "" {
+		noBuildPkgs = append(noBuildPkgs, fw)
+	}
+	if e := cfg.EEPROMPackageOrDefault(); e != "" {
+		noBuildPkgs = append(noBuildPkgs, e)
+	}
+	setUmask()
+	buildEnv := &packer.BuildEnv{
+		BuildDir: packer.BuildDirOrMigrate,
+	}
+	var buildErr error
+	trace.WithRegion(context.Background(), "build", func() {
+		buildErr = buildEnv.Build(bindir, pkgs, pack.packageBuildFlags, pack.packageBuildTags, pack.packageBuildEnv, noBuildPkgs, pack.basenames)
+	})
+	if buildErr != nil {
+		return buildErr
+	}
+
+	log.Printf("")
+
+	var err error
+	trace.WithRegion(context.Background(), "validate", func() {
+		err = pack.validateTargetArchMatchesKernel()
+	})
+	if err != nil {
+		return err
+	}
+
+	var (
+		root      *FileInfo
+		foundBins []foundBin
+	)
+	trace.WithRegion(context.Background(), "findbins", func() {
+		root, foundBins, err = findBins(cfg, buildEnv, bindir, pack.basenames)
+	})
+	if err != nil {
+		return err
+	}
+	pack.root = root
+
+	packageConfigFiles = make(map[string][]packageConfigFile)
+
+	var extraFiles map[string][]*FileInfo
+	trace.WithRegion(context.Background(), "findextrafiles", func() {
+		extraFiles, err = FindExtraFiles(cfg)
+	})
+	if err != nil {
+		return err
+	}
+	for _, packageExtraFiles := range extraFiles {
+		for _, ef := range packageExtraFiles {
+			for _, de := range ef.Dirents {
+				if de.Filename != "perm" {
+					continue
+				}
+				return fmt.Errorf("invalid ExtraFilePaths or ExtraFileContents: cannot write extra files to user-controlled /perm partition")
+			}
+		}
+	}
+
+	if len(packageConfigFiles) > 0 {
+		log.Printf("Including extra files for Go packages:")
+		log.Printf("")
+		for _, pkg := range args {
+			if len(packageConfigFiles[pkg]) == 0 {
+				continue
+			}
+			log.Printf("  %s", pkg)
+			for _, configFile := range packageConfigFiles[pkg] {
+				log.Printf("    will %s",
+					configFile.kind)
+				log.Printf("      from %s",
+					configFile.path)
+				log.Printf("      last modified: %s (%s ago)",
+					configFile.lastModified.Format(time.RFC3339),
+					time.Since(configFile.lastModified).Round(1*time.Second))
+			}
+			log.Printf("")
+		}
+	}
+
+	if cfg.InternalCompatibilityFlags.InitPkg == "" {
+		gokrazyInit := &gokrazyInit{
+			root:             root,
+			flagFileContents: pack.flagFileContents,
+			envFileContents:  pack.envFileContents,
+			buildTimestamp:   pack.buildTimestamp,
+			dontStart:        pack.dontStart,
+			waitForClock:     pack.waitForClock,
+			basenames:        pack.basenames,
+		}
+		if cfg.InternalCompatibilityFlags.OverwriteInit != "" {
+			return gokrazyInit.dump(cfg.InternalCompatibilityFlags.OverwriteInit)
+		}
+
+		var tmpdir string
+		trace.WithRegion(context.Background(), "buildinit", func() {
+			tmpdir, err = gokrazyInit.build()
+		})
+		if err != nil {
+			return err
+		}
+		pack.initTmp = tmpdir
+
+		initPath := filepath.Join(tmpdir, "init")
+
+		fileIsELFOrFatal(initPath)
+
+		gokrazy := root.mustFindDirent("gokrazy")
+		gokrazy.Dirents = append(gokrazy.Dirents, &FileInfo{
+			Filename: "init",
+			FromHost: initPath,
+		})
+	}
+
+	defaultPassword, updateHostname := updateflag.Value{
+		Update: cfg.InternalCompatibilityFlags.Update,
+	}.GetUpdateTarget(cfg.Hostname)
+	update, err := cfg.Update.WithFallbackToHostSpecific(cfg.Hostname)
+	if err != nil {
+		return err
+	}
+
+	if update.HTTPPort == "" {
+		update.HTTPPort = "80"
+	}
+
+	if update.HTTPSPort == "" {
+		update.HTTPSPort = "443"
+	}
+
+	if update.Hostname == "" {
+		update.Hostname = updateHostname
+	}
+
+	if update.HTTPPassword == "" && !update.NoPassword {
+		pw, err := ensurePasswordFileExists(updateHostname, defaultPassword)
+		if err != nil {
+			return err
+		}
+		update.HTTPPassword = pw
+	}
+
+	pack.update = update
+
+	for _, dir := range []string{"bin", "dev", "etc", "proc", "sys", "tmp", "perm", "lib", "run", "mnt"} {
+		root.Dirents = append(root.Dirents, &FileInfo{
+			Filename: dir,
+		})
+	}
+
+	root.Dirents = append(root.Dirents, &FileInfo{
+		Filename:    "var",
+		SymlinkDest: "/perm/var",
+	})
+
+	mnt := root.mustFindDirent("mnt")
+	for _, md := range cfg.MountDevices {
+		if !strings.HasPrefix(md.Target, "/mnt/") {
+			continue
+		}
+		rest := strings.TrimPrefix(md.Target, "/mnt/")
+		rest = strings.TrimSuffix(rest, "/")
+		if strings.Contains(rest, "/") {
+			continue
+		}
+		mnt.Dirents = append(mnt.Dirents, &FileInfo{
+			Filename: rest,
+		})
+	}
+
+	// include lib/modules from kernelPackage dir, if present
+	kernelDir, err := packer.PackageDir(cfg.KernelPackageOrDefault())
+	if err != nil {
+		return err
+	}
+	pack.kernelDir = kernelDir
+	modulesDir := filepath.Join(kernelDir, "lib", "modules")
+	if _, err := os.Stat(modulesDir); err == nil {
+		log.Printf("Including loadable kernel modules from:")
+		log.Printf("  %s", modulesDir)
+		modules := &FileInfo{
+			Filename: "modules",
+		}
+		trace.WithRegion(context.Background(), "kernelmod", func() {
+			_, err = addToFileInfo(modules, modulesDir)
+		})
+		if err != nil {
+			return err
+		}
+		lib := root.mustFindDirent("lib")
+		lib.Dirents = append(lib.Dirents, modules)
+	}
+
+	etc := root.mustFindDirent("etc")
+	tmpdir, err := os.MkdirTemp("", "gokrazy")
+	if err != nil {
+		return err
+	}
+	defer os.RemoveAll(tmpdir)
+	hostLocaltime, err := hostLocaltime(tmpdir)
+	if err != nil {
+		return err
+	}
+	if hostLocaltime != "" {
+		etc.Dirents = append(etc.Dirents, &FileInfo{
+			Filename: "localtime",
+			FromHost: hostLocaltime,
+		})
+	}
+	etc.Dirents = append(etc.Dirents, &FileInfo{
+		Filename:    "resolv.conf",
+		SymlinkDest: "/tmp/resolv.conf",
+	})
+	etc.Dirents = append(etc.Dirents, &FileInfo{
+		Filename: "hosts",
+		FromLiteral: `127.0.0.1 localhost
+::1 localhost
+`,
+	})
+	etc.Dirents = append(etc.Dirents, &FileInfo{
+		Filename:    "hostname",
+		FromLiteral: cfg.Hostname,
+	})
+
+	ssl := &FileInfo{Filename: "ssl"}
+	ssl.Dirents = append(ssl.Dirents, &FileInfo{
+		Filename:    "ca-bundle.pem",
+		FromLiteral: pack.systemCertsPEM,
+	})
+
+	pack.schema = "http"
+	if update.CertPEM == "" || update.KeyPEM == "" {
+		deployCertFile, deployKeyFile, err := getCertificate(cfg)
+		if err != nil {
+			return err
+		}
+
+		if deployCertFile != "" {
+			b, err := os.ReadFile(deployCertFile)
+			if err != nil {
+				return err
+			}
+			update.CertPEM = strings.TrimSpace(string(b))
+
+			b, err = os.ReadFile(deployKeyFile)
+			if err != nil {
+				return err
+			}
+			update.KeyPEM = strings.TrimSpace(string(b))
+		}
+	}
+	if update.CertPEM != "" && update.KeyPEM != "" {
+		// User requested TLS
+		pack.schema = "https"
+
+		ssl.Dirents = append(ssl.Dirents, &FileInfo{
+			Filename:    "gokrazy-web.pem",
+			FromLiteral: update.CertPEM,
+		})
+		ssl.Dirents = append(ssl.Dirents, &FileInfo{
+			Filename:    "gokrazy-web.key.pem",
+			FromLiteral: update.KeyPEM,
+		})
+	}
+
+	etc.Dirents = append(etc.Dirents, ssl)
+
+	if !update.NoPassword {
+		etc.Dirents = append(etc.Dirents, &FileInfo{
+			Filename:    "gokr-pw.txt",
+			Mode:        0400,
+			FromLiteral: update.HTTPPassword,
+		})
+	}
+
+	etc.Dirents = append(etc.Dirents, &FileInfo{
+		Filename:    "http-port.txt",
+		FromLiteral: update.HTTPPort,
+	})
+
+	etc.Dirents = append(etc.Dirents, &FileInfo{
+		Filename:    "https-port.txt",
+		FromLiteral: update.HTTPSPort,
+	})
+
+	// GenerateSBOM() must be provided with a cfg
+	// that hasn't been modified by gok at runtime,
+	// as the SBOM should reflect what’s going into gokrazy,
+	// not its internal implementation details
+	// (i.e.  cfg.InternalCompatibilityFlags untouched).
+	var sbom []byte
+	var sbomWithHash SBOMWithHash
+	trace.WithRegion(context.Background(), "sbom", func() {
+		sbom, sbomWithHash, err = generateSBOM(pack.FileCfg, foundBins)
+	})
+	if err != nil {
+		return err
+	}
+	pack.sbom = sbom
+	pack.sbomWithHash = sbomWithHash
+
+	etcGokrazy := &FileInfo{Filename: "gokrazy"}
+	etcGokrazy.Dirents = append(etcGokrazy.Dirents, &FileInfo{
+		Filename:    "sbom.json",
+		FromLiteral: string(sbom),
+	})
+	mountdevices, err := json.Marshal(cfg.MountDevices)
+	if err != nil {
+		return err
+	}
+	etcGokrazy.Dirents = append(etcGokrazy.Dirents, &FileInfo{
+		Filename:    "mountdevices.json",
+		FromLiteral: string(mountdevices),
+	})
+	etc.Dirents = append(etc.Dirents, etcGokrazy)
+
+	empty := &FileInfo{Filename: ""}
+	if paths := getDuplication(root, empty); len(paths) > 0 {
+		return fmt.Errorf("root file system contains duplicate files: your config contains multiple packages that install %s", paths)
+	}
+
+	for pkg1, fs := range extraFiles {
+		for _, fs1 := range fs {
+			// check against root fs
+			if paths := getDuplication(root, fs1); len(paths) > 0 {
+				return fmt.Errorf("extra files of package %s collides with root file system: %v", pkg1, paths)
+			}
+
+			// check against other packages
+			for pkg2, fs := range extraFiles {
+				for _, fs2 := range fs {
+					if pkg1 == pkg2 {
+						continue
+					}
+
+					if paths := getDuplication(fs1, fs2); len(paths) > 0 {
+						return fmt.Errorf("extra files of package %s collides with package %s: %v", pkg1, pkg2, paths)
+					}
+				}
+			}
+
+			// add extra files to rootfs
+			if err := root.combine(fs1); err != nil {
+				return fmt.Errorf("failed to add extra files from package %s: %v", pkg1, err)
+			}
+		}
+	}
+
+	return nil
+}

internal/packer/packerprepare.go

@@ -0,0 +1,591 @@
+package packer
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"time"
+
+	"github.com/gokrazy/internal/config"
+	"github.com/gokrazy/internal/deviceconfig"
+	"github.com/gokrazy/tools/internal/cap"
+	"github.com/gokrazy/tools/internal/version"
+	"github.com/gokrazy/tools/packer"
+)
+
+type filePathAndModTime struct {
+	path    string
+	modTime time.Time
+}
+
+func findPackageFiles(fileType string) ([]filePathAndModTime, error) {
+	var packageFilePaths []filePathAndModTime
+	err := filepath.Walk(fileType, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+		if info != nil && !info.Mode().IsRegular() {
+			return nil
+		}
+		if strings.HasSuffix(path, fmt.Sprintf("/%s.txt", fileType)) {
+			packageFilePaths = append(packageFilePaths, filePathAndModTime{
+				path:    path,
+				modTime: info.ModTime(),
+			})
+		}
+		return nil
+	})
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, nil // no fileType directory found
+		}
+	}
+
+	return packageFilePaths, nil
+}
+func (pack *Pack) logicPrepare(ctx context.Context) error {
+	log := pack.Env.Logger()
+	cfg := pack.Cfg
+
+	if cfg.InternalCompatibilityFlags.Update != "" &&
+		cfg.InternalCompatibilityFlags.Overwrite != "" {
+		return fmt.Errorf("both -update and -overwrite are specified; use either one, not both")
+	}
+
+	// Check early on if the destination is a device that is mounted
+	// so that the user does not get the impression that everything
+	// is fine and about to complete after a lengthy build phase.
+	// See also https://github.com/gokrazy/gokrazy/discussions/308
+	switch {
+	case cfg.InternalCompatibilityFlags.Overwrite != "" ||
+		(pack.Output != nil && pack.Output.Type == OutputTypeFull && pack.Output.Path != ""):
+
+		target := cfg.InternalCompatibilityFlags.Overwrite
+		st, err := os.Stat(target)
+		if err != nil && !os.IsNotExist(err) {
+			return err
+		}
+
+		if err == nil && st.Mode()&os.ModeDevice == os.ModeDevice {
+			if err := verifyNotMounted(target); err != nil {
+				return fmt.Errorf("cannot overwrite %s: %v (perhaps automatically?)\n  please unmount all partitions and retry", target, err)
+			}
+		}
+	}
+
+	var mbrOnlyWithoutGpt bool
+	pack.firstPartitionOffsetSectors = deviceconfig.DefaultBootPartitionStartLBA
+	if cfg.DeviceType != "" {
+		if devcfg, ok := deviceconfig.GetDeviceConfigBySlug(cfg.DeviceType); ok {
+			pack.rootDeviceFiles = devcfg.RootDeviceFiles
+			mbrOnlyWithoutGpt = devcfg.MBROnlyWithoutGPT
+			if devcfg.BootPartitionStartLBA != 0 {
+				pack.firstPartitionOffsetSectors = devcfg.BootPartitionStartLBA
+			}
+		} else {
+			return fmt.Errorf("unknown device slug %q", cfg.DeviceType)
+		}
+	}
+
+	pack.Pack = packer.NewPackForHost(pack.firstPartitionOffsetSectors, cfg.Hostname)
+
+	newInstallation := cfg.InternalCompatibilityFlags.Update == ""
+	useGPT := newInstallation && !mbrOnlyWithoutGpt
+
+	pack.Pack.UsePartuuid = newInstallation
+	pack.Pack.UseGPTPartuuid = useGPT
+	pack.Pack.UseGPT = useGPT
+
+	if os.Getenv("GOKR_PACKER_FD") != "" { // partitioning child process
+		if _, err := pack.SudoPartition(cfg.InternalCompatibilityFlags.Overwrite); err != nil {
+			log.Printf("%s", err)
+			os.Exit(1)
+		}
+		os.Exit(0)
+	}
+
+	log.Printf("%s %s on GOARCH=%s GOOS=%s",
+		programName,
+		version.ReadBrief(),
+		runtime.GOARCH,
+		runtime.GOOS)
+	log.Printf("")
+
+	if cfg.InternalCompatibilityFlags.Update != "" {
+		// TODO: fix update URL:
+		log.Printf("Updating gokrazy installation on http://%s", cfg.Hostname)
+		log.Printf("")
+	}
+
+	log.Printf("Build target: %s", strings.Join(filterGoEnv(packer.Env()), " "))
+
+	pack.buildTimestamp = time.Now().Format(time.RFC3339)
+	if ts, ok := ctx.Value(BuildTimestampOverride).(string); ok {
+		pack.buildTimestamp = ts
+	}
+	log.Printf("Build timestamp: %s", pack.buildTimestamp)
+
+	systemCertsPEM, err := pack.findSystemCertsPEM()
+	if err != nil {
+		return err
+	}
+	pack.systemCertsPEM = systemCertsPEM
+
+	packageBuildFlags, err := pack.findBuildFlagsFiles(cfg)
+	if err != nil {
+		return err
+	}
+	pack.packageBuildFlags = packageBuildFlags
+
+	packageBuildTags, err := pack.findBuildTagsFiles(cfg)
+	if err != nil {
+		return err
+	}
+	pack.packageBuildTags = packageBuildTags
+
+	packageBuildEnv, err := findBuildEnv(cfg)
+	if err != nil {
+		return err
+	}
+	pack.packageBuildEnv = packageBuildEnv
+
+	flagFileContents, err := pack.findFlagFiles(cfg)
+	if err != nil {
+		return err
+	}
+	pack.flagFileContents = flagFileContents
+
+	envFileContents, err := pack.findEnvFiles(cfg)
+	if err != nil {
+		return err
+	}
+	pack.envFileContents = envFileContents
+
+	dontStart, err := pack.findDontStart(cfg)
+	if err != nil {
+		return err
+	}
+	pack.dontStart = dontStart
+
+	waitForClock, err := pack.findWaitForClock(cfg)
+	if err != nil {
+		return err
+	}
+	pack.waitForClock = waitForClock
+
+	basenames, err := findBasenames(cfg)
+	if err != nil {
+		return err
+	}
+	pack.basenames = basenames
+
+	capabilities, err := findCapabilities(cfg)
+	if err != nil {
+		return err
+	}
+	pack.xattrs = capabilities
+
+	return nil
+}
+
+func (pack *Pack) findFlagFiles(cfg *config.Struct) (map[string][]string, error) {
+	log := pack.Env.Logger()
+
+	if len(cfg.PackageConfig) > 0 {
+		contents := make(map[string][]string)
+		for pkg, packageConfig := range cfg.PackageConfig {
+			if len(packageConfig.CommandLineFlags) == 0 {
+				continue
+			}
+			contents[pkg] = packageConfig.CommandLineFlags
+			packageConfigFiles[pkg] = append(packageConfigFiles[pkg], packageConfigFile{
+				kind:         "be started with command-line flags",
+				path:         cfg.Meta.Path,
+				lastModified: cfg.Meta.LastModified,
+			})
+		}
+		return contents, nil
+	}
+
+	flagFilePaths, err := findPackageFiles("flags")
+	if err != nil {
+		return nil, err
+	}
+
+	if len(flagFilePaths) == 0 {
+		return nil, nil // no flags.txt files found
+	}
+
+	buildPackages := buildPackageMapFromFlags(cfg)
+
+	contents := make(map[string][]string)
+	for _, p := range flagFilePaths {
+		pkg := strings.TrimSuffix(strings.TrimPrefix(p.path, "flags/"), "/flags.txt")
+		if !buildPackages[pkg] {
+			log.Printf("WARNING: flag file %s does not match any specified package (%s)", pkg, cfg.Packages)
+			continue
+		}
+		packageConfigFiles[pkg] = append(packageConfigFiles[pkg], packageConfigFile{
+			kind:         "be started with command-line flags",
+			path:         p.path,
+			lastModified: p.modTime,
+		})
+
+		b, err := os.ReadFile(p.path)
+		if err != nil {
+			return nil, err
+		}
+		lines := strings.Split(strings.TrimSpace(string(b)), "\n")
+		contents[pkg] = lines
+	}
+
+	return contents, nil
+}
+
+func (pack *Pack) findBuildFlagsFiles(cfg *config.Struct) (map[string][]string, error) {
+	log := pack.Env.Logger()
+
+	if len(cfg.PackageConfig) > 0 {
+		contents := make(map[string][]string)
+		for pkg, packageConfig := range cfg.PackageConfig {
+			if len(packageConfig.GoBuildFlags) == 0 {
+				continue
+			}
+			contents[pkg] = packageConfig.GoBuildFlags
+			packageConfigFiles[pkg] = append(packageConfigFiles[pkg], packageConfigFile{
+				kind:         "be compiled with build flags",
+				path:         cfg.Meta.Path,
+				lastModified: cfg.Meta.LastModified,
+			})
+		}
+		return contents, nil
+	}
+
+	buildFlagsFilePaths, err := findPackageFiles("buildflags")
+	if err != nil {
+		return nil, err
+	}
+
+	if len(buildFlagsFilePaths) == 0 {
+		return nil, nil // no flags.txt files found
+	}
+
+	buildPackages := buildPackageMapFromFlags(cfg)
+
+	contents := make(map[string][]string)
+	for _, p := range buildFlagsFilePaths {
+		pkg := strings.TrimSuffix(strings.TrimPrefix(p.path, "buildflags/"), "/buildflags.txt")
+		if !buildPackages[pkg] {
+			log.Printf("WARNING: buildflags file %s does not match any specified package (%s)", pkg, cfg.Packages)
+			continue
+		}
+		packageConfigFiles[pkg] = append(packageConfigFiles[pkg], packageConfigFile{
+			kind:         "be compiled with build flags",
+			path:         p.path,
+			lastModified: p.modTime,
+		})
+
+		b, err := os.ReadFile(p.path)
+		if err != nil {
+			return nil, err
+		}
+
+		var buildFlags []string
+		sc := bufio.NewScanner(strings.NewReader(string(b)))
+		for sc.Scan() {
+			if flag := sc.Text(); flag != "" {
+				buildFlags = append(buildFlags, flag)
+			}
+		}
+
+		if err := sc.Err(); err != nil {
+			return nil, err
+		}
+
+		// use full package path opposed to flags
+		contents[pkg] = buildFlags
+	}
+
+	return contents, nil
+}
+
+func findBuildEnv(cfg *config.Struct) (map[string][]string, error) {
+	contents := make(map[string][]string)
+	for pkg, packageConfig := range cfg.PackageConfig {
+		if len(packageConfig.GoBuildEnvironment) == 0 {
+			continue
+		}
+		contents[pkg] = packageConfig.GoBuildEnvironment
+		packageConfigFiles[pkg] = append(packageConfigFiles[pkg], packageConfigFile{
+			kind:         "be compiled with build environment variables",
+			path:         cfg.Meta.Path,
+			lastModified: cfg.Meta.LastModified,
+		})
+	}
+	return contents, nil
+}
+
+func (pack *Pack) findBuildTagsFiles(cfg *config.Struct) (map[string][]string, error) {
+	log := pack.Env.Logger()
+
+	if len(cfg.PackageConfig) > 0 {
+		contents := make(map[string][]string)
+		for pkg, packageConfig := range cfg.PackageConfig {
+			if len(packageConfig.GoBuildTags) == 0 {
+				continue
+			}
+			contents[pkg] = packageConfig.GoBuildTags
+			packageConfigFiles[pkg] = append(packageConfigFiles[pkg], packageConfigFile{
+				kind:         "be compiled with build tags",
+				path:         cfg.Meta.Path,
+				lastModified: cfg.Meta.LastModified,
+			})
+		}
+		return contents, nil
+	}
+
+	buildTagsFiles, err := findPackageFiles("buildtags")
+	if err != nil {
+		return nil, err
+	}
+
+	if len(buildTagsFiles) == 0 {
+		return nil, nil // no flags.txt files found
+	}
+
+	buildPackages := buildPackageMapFromFlags(cfg)
+
+	contents := make(map[string][]string)
+	for _, p := range buildTagsFiles {
+		pkg := strings.TrimSuffix(strings.TrimPrefix(p.path, "buildtags/"), "/buildtags.txt")
+		if !buildPackages[pkg] {
+			log.Printf("WARNING: buildtags file %s does not match any specified package (%s)", pkg, cfg.Packages)
+			continue
+		}
+		packageConfigFiles[pkg] = append(packageConfigFiles[pkg], packageConfigFile{
+			kind:         "be compiled with build tags",
+			path:         p.path,
+			lastModified: p.modTime,
+		})
+
+		b, err := os.ReadFile(p.path)
+		if err != nil {
+			return nil, err
+		}
+
+		var buildTags []string
+		sc := bufio.NewScanner(strings.NewReader(string(b)))
+		for sc.Scan() {
+			if flag := sc.Text(); flag != "" {
+				buildTags = append(buildTags, flag)
+			}
+		}
+
+		if err := sc.Err(); err != nil {
+			return nil, err
+		}
+
+		// use full package path opposed to flags
+		contents[pkg] = buildTags
+	}
+
+	return contents, nil
+}
+
+func (pack *Pack) findEnvFiles(cfg *config.Struct) (map[string][]string, error) {
+	log := pack.Env.Logger()
+
+	if len(cfg.PackageConfig) > 0 {
+		contents := make(map[string][]string)
+		for pkg, packageConfig := range cfg.PackageConfig {
+			if len(packageConfig.Environment) == 0 {
+				continue
+			}
+			contents[pkg] = packageConfig.Environment
+			packageConfigFiles[pkg] = append(packageConfigFiles[pkg], packageConfigFile{
+				kind:         "be started with environment variables",
+				path:         cfg.Meta.Path,
+				lastModified: cfg.Meta.LastModified,
+			})
+		}
+		return contents, nil
+	}
+
+	buildFlagsFilePaths, err := findPackageFiles("env")
+	if err != nil {
+		return nil, err
+	}
+
+	if len(buildFlagsFilePaths) == 0 {
+		return nil, nil // no flags.txt files found
+	}
+
+	buildPackages := buildPackageMapFromFlags(cfg)
+
+	contents := make(map[string][]string)
+	for _, p := range buildFlagsFilePaths {
+		pkg := strings.TrimSuffix(strings.TrimPrefix(p.path, "env/"), "/env.txt")
+		if !buildPackages[pkg] {
+			log.Printf("WARNING: environment variable file %s does not match any specified package (%s)", pkg, cfg.Packages)
+			continue
+		}
+		packageConfigFiles[pkg] = append(packageConfigFiles[pkg], packageConfigFile{
+			kind:         "be started with environment variables",
+			path:         p.path,
+			lastModified: p.modTime,
+		})
+
+		b, err := os.ReadFile(p.path)
+		if err != nil {
+			return nil, err
+		}
+		lines := strings.Split(strings.TrimSpace(string(b)), "\n")
+		contents[pkg] = lines
+	}
+
+	return contents, nil
+}
+
+func (pack *Pack) findDontStart(cfg *config.Struct) (map[string]bool, error) {
+	log := pack.Env.Logger()
+
+	if len(cfg.PackageConfig) > 0 {
+		contents := make(map[string]bool)
+		for pkg, packageConfig := range cfg.PackageConfig {
+			if !packageConfig.DontStart {
+				continue
+			}
+			contents[pkg] = packageConfig.DontStart
+			packageConfigFiles[pkg] = append(packageConfigFiles[pkg], packageConfigFile{
+				kind:         "not be started at boot",
+				path:         cfg.Meta.Path,
+				lastModified: cfg.Meta.LastModified,
+			})
+		}
+		return contents, nil
+	}
+
+	dontStartPaths, err := findPackageFiles("dontstart")
+	if err != nil {
+		return nil, err
+	}
+
+	if len(dontStartPaths) == 0 {
+		return nil, nil // no dontstart.txt files found
+	}
+
+	buildPackages := buildPackageMapFromFlags(cfg)
+
+	contents := make(map[string]bool)
+	for _, p := range dontStartPaths {
+		pkg := strings.TrimSuffix(strings.TrimPrefix(p.path, "dontstart/"), "/dontstart.txt")
+		if !buildPackages[pkg] {
+			log.Printf("WARNING: dontstart.txt file %s does not match any specified package (%s)", pkg, cfg.Packages)
+			continue
+		}
+		packageConfigFiles[pkg] = append(packageConfigFiles[pkg], packageConfigFile{
+			kind:         "not be started at boot",
+			path:         p.path,
+			lastModified: p.modTime,
+		})
+
+		contents[pkg] = true
+	}
+
+	return contents, nil
+}
+
+func (pack *Pack) findWaitForClock(cfg *config.Struct) (map[string]bool, error) {
+	log := pack.Env.Logger()
+
+	if len(cfg.PackageConfig) > 0 {
+		contents := make(map[string]bool)
+		for pkg, packageConfig := range cfg.PackageConfig {
+			if !packageConfig.WaitForClock {
+				continue
+			}
+			contents[pkg] = packageConfig.WaitForClock
+			packageConfigFiles[pkg] = append(packageConfigFiles[pkg], packageConfigFile{
+				kind:         "wait for clock synchronization before start",
+				path:         cfg.Meta.Path,
+				lastModified: cfg.Meta.LastModified,
+			})
+		}
+		return contents, nil
+	}
+
+	waitForClockPaths, err := findPackageFiles("waitforclock")
+	if err != nil {
+		return nil, err
+	}
+
+	if len(waitForClockPaths) == 0 {
+		return nil, nil // no waitforclock.txt files found
+	}
+
+	buildPackages := buildPackageMapFromFlags(cfg)
+
+	contents := make(map[string]bool)
+	for _, p := range waitForClockPaths {
+		pkg := strings.TrimSuffix(strings.TrimPrefix(p.path, "waitforclock/"), "/waitforclock.txt")
+		if !buildPackages[pkg] {
+			log.Printf("WARNING: waitforclock.txt file %s does not match any specified package (%s)", pkg, cfg.Packages)
+			continue
+		}
+		packageConfigFiles[pkg] = append(packageConfigFiles[pkg], packageConfigFile{
+			kind:         "wait for clock synchronization before start",
+			path:         p.path,
+			lastModified: p.modTime,
+		})
+
+		contents[pkg] = true
+	}
+
+	return contents, nil
+}
+
+func findBasenames(cfg *config.Struct) (map[string]string, error) {
+	contents := make(map[string]string)
+	for pkg, packageConfig := range cfg.PackageConfig {
+		if packageConfig.Basename == "" {
+			continue
+		}
+		contents[pkg] = packageConfig.Basename
+		packageConfigFiles[pkg] = append(packageConfigFiles[pkg], packageConfigFile{
+			kind: "be installed with the basename set to " + packageConfig.Basename,
+		})
+	}
+	return contents, nil
+}
+
+func findCapabilities(cfg *config.Struct) (map[string]map[string][]byte, error) {
+	contents := make(map[string]map[string][]byte)
+	for pkg, packageConfig := range cfg.PackageConfig {
+		if packageConfig.Capabilities == "" {
+			continue
+		}
+		set, err := cap.FromText(packageConfig.Capabilities)
+		if err != nil {
+			return nil, fmt.Errorf("Unable to parse capabilities: %s: %w", packageConfig.Capabilities, err)
+		}
+		xattrValue, err := set.PackFileCap()
+		if err != nil {
+			return nil, fmt.Errorf("Unable to pack capabilities: %s: %w", packageConfig.Capabilities, err) // This should basically never happen
+		}
+		set, err = cap.DigestFileCap(xattrValue)
+		if err != nil {
+			return nil, fmt.Errorf("Error checking packed capabilities: %s: %w", packageConfig.Capabilities, err) // This should also never happen
+		}
+		contents[pkg] = map[string][]byte{
+			"security.capability": xattrValue,
+		}
+		packageConfigFiles[pkg] = append(packageConfigFiles[pkg], packageConfigFile{
+			kind: "be installed with file capabilities " + set.String(),
+		})
+	}
+	return contents, nil
+}

internal/packer/packerupdate.go

@@ -0,0 +1,253 @@
+package packer
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"path/filepath"
+	"syscall"
+	"time"
+
+	"github.com/gokrazy/internal/httpclient"
+	"github.com/gokrazy/internal/humanize"
+	"github.com/gokrazy/internal/progress"
+	"github.com/gokrazy/internal/updateflag"
+	"github.com/gokrazy/updater"
+)
+
+func (pack *Pack) logicUpdate(ctx context.Context, isDev bool, bootSize int64, rootSize int64, tmpMBR, tmpBoot, tmpRoot *os.File, updateBaseUrl *url.URL, target *updater.Target, updateHttpClient *http.Client) error {
+	log := pack.Env.Logger()
+	cfg := pack.Cfg       // for convenience
+	update := pack.update // for convenience
+
+	var rootReader, bootReader, mbrReader io.Reader
+	// Determine where to read the boot, root and MBR images from.
+	switch {
+	case cfg.InternalCompatibilityFlags.Overwrite != "":
+		if isDev {
+			bootFile, err := os.Open(cfg.InternalCompatibilityFlags.Overwrite + "1")
+			if err != nil {
+				return err
+			}
+			bootReader = bootFile
+			rootFile, err := os.Open(cfg.InternalCompatibilityFlags.Overwrite + "2")
+			if err != nil {
+				return err
+			}
+			rootReader = rootFile
+		} else {
+			bootFile, err := os.Open(cfg.InternalCompatibilityFlags.Overwrite)
+			if err != nil {
+				return err
+			}
+			if _, err := bootFile.Seek(pack.firstPartitionOffsetSectors*512, io.SeekStart); err != nil {
+				return err
+			}
+			bootReader = &io.LimitedReader{
+				R: bootFile,
+				N: bootSize,
+			}
+
+			rootFile, err := os.Open(cfg.InternalCompatibilityFlags.Overwrite)
+			if err != nil {
+				return err
+			}
+			if _, err := rootFile.Seek(pack.firstPartitionOffsetSectors*512+100*MB, io.SeekStart); err != nil {
+				return err
+			}
+			rootReader = &io.LimitedReader{
+				R: rootFile,
+				N: rootSize,
+			}
+		}
+		mbrFile, err := os.Open(cfg.InternalCompatibilityFlags.Overwrite)
+		if err != nil {
+			return err
+		}
+		mbrReader = &io.LimitedReader{
+			R: mbrFile,
+			N: 446,
+		}
+
+	default:
+		if cfg.InternalCompatibilityFlags.OverwriteBoot != "" {
+			bootFile, err := os.Open(cfg.InternalCompatibilityFlags.OverwriteBoot)
+			if err != nil {
+				return err
+			}
+			bootReader = bootFile
+			if cfg.InternalCompatibilityFlags.OverwriteMBR != "" {
+				mbrFile, err := os.Open(cfg.InternalCompatibilityFlags.OverwriteMBR)
+				if err != nil {
+					return err
+				}
+				mbrReader = mbrFile
+			} else {
+				if _, err := tmpMBR.Seek(0, io.SeekStart); err != nil {
+					return err
+				}
+				mbrReader = tmpMBR
+			}
+		}
+
+		if cfg.InternalCompatibilityFlags.OverwriteRoot != "" {
+			rootFile, err := os.Open(cfg.InternalCompatibilityFlags.OverwriteRoot)
+			if err != nil {
+				return err
+			}
+			rootReader = rootFile
+		}
+
+		if cfg.InternalCompatibilityFlags.OverwriteBoot == "" && cfg.InternalCompatibilityFlags.OverwriteRoot == "" {
+			if _, err := tmpBoot.Seek(0, io.SeekStart); err != nil {
+				return err
+			}
+			bootReader = tmpBoot
+
+			if _, err := tmpMBR.Seek(0, io.SeekStart); err != nil {
+				return err
+			}
+			mbrReader = tmpMBR
+
+			if _, err := tmpRoot.Seek(0, io.SeekStart); err != nil {
+				return err
+			}
+			rootReader = tmpRoot
+		}
+	}
+
+	updateBaseUrl.Path = "/"
+	log.Printf("Updating %s", updateBaseUrl.String())
+
+	progctx, canc := context.WithCancel(context.Background())
+	defer canc()
+	prog := &progress.Reporter{}
+	go prog.Report(progctx)
+
+	// Start with the root file system because writing to the non-active
+	// partition cannot break the currently running system.
+	if err := pack.updateWithProgress(prog, rootReader, target, "root file system", "root"); err != nil {
+		return err
+	}
+
+	for _, rootDeviceFile := range pack.rootDeviceFiles {
+		f, err := os.Open(filepath.Join(pack.kernelDir, rootDeviceFile.Name))
+		if err != nil {
+			return err
+		}
+
+		if err := pack.updateWithProgress(
+			prog, f, target, fmt.Sprintf("root device file %s", rootDeviceFile.Name),
+			filepath.Join("device-specific", rootDeviceFile.Name),
+		); err != nil {
+			if errors.Is(err, updater.ErrUpdateHandlerNotImplemented) {
+				log.Printf("target does not support updating device file %s yet, ignoring", rootDeviceFile.Name)
+				continue
+			}
+			return err
+		}
+	}
+
+	if err := pack.updateWithProgress(prog, bootReader, target, "boot file system", "boot"); err != nil {
+		return err
+	}
+
+	if err := target.StreamTo(ctx, "mbr", mbrReader); err != nil {
+		if err == updater.ErrUpdateHandlerNotImplemented {
+			log.Printf("target does not support updating MBR yet, ignoring")
+		} else {
+			return fmt.Errorf("updating MBR: %v", err)
+		}
+	}
+
+	if cfg.InternalCompatibilityFlags.Testboot {
+		if err := target.Testboot(ctx); err != nil {
+			return fmt.Errorf("enable testboot of non-active partition: %v", err)
+		}
+	} else {
+		if err := target.Switch(ctx); err != nil {
+			return fmt.Errorf("switching to non-active partition: %v", err)
+		}
+	}
+
+	// Stop progress reporting to not mess up the following logs output.
+	canc()
+
+	log.Printf("Triggering reboot")
+	if err := target.Reboot(ctx); err != nil {
+		if errors.Is(err, syscall.ECONNRESET) {
+			log.Printf("ignoring reboot error: %v", err)
+		} else {
+			return fmt.Errorf("reboot: %v", err)
+		}
+	}
+
+	const polltimeout = 5 * time.Minute
+	log.Printf("Updated, waiting %v for the device to become reachable (cancel with Ctrl-C any time)", polltimeout)
+
+	if update.CertPEM != "" && update.KeyPEM != "" {
+		// Use an HTTPS client (post-update),
+		// even when the --insecure flag was specified.
+		pack.schema = "https"
+		var err error
+		updateBaseUrl, err = updateflag.Value{
+			Update: "yes",
+		}.BaseURL(update.HTTPPort, update.HTTPSPort, pack.schema, update.Hostname, update.HTTPPassword)
+		if err != nil {
+			return err
+		}
+		updateHttpClient, _, err = httpclient.GetTLSHttpClientByTLSFlag(update.UseTLS, false /* insecure */, updateBaseUrl)
+		if err != nil {
+			return fmt.Errorf("getting http client by tls flag: %v", err)
+		}
+	}
+
+	pollctx, canc := context.WithTimeout(context.Background(), polltimeout)
+	defer canc()
+	for {
+		if err := pollctx.Err(); err != nil {
+			return fmt.Errorf("device did not become healthy after update (%v)", err)
+		}
+		if err := pollUpdated1(pollctx, updateHttpClient, updateBaseUrl.String(), pack.buildTimestamp); err != nil {
+			log.Printf("device not yet reachable: %v", err)
+			time.Sleep(1 * time.Second)
+			continue
+		}
+
+		log.Printf("Device ready to use!")
+		break
+	}
+
+	return nil
+}
+
+func (pack *Pack) updateWithProgress(prog *progress.Reporter, reader io.Reader, target *updater.Target, logStr string, stream string) error {
+	ctx := context.Background()
+	log := pack.Env.Logger()
+
+	start := time.Now()
+	prog.SetStatus(fmt.Sprintf("update %s", logStr))
+	prog.SetTotal(0)
+
+	if stater, ok := reader.(interface{ Stat() (os.FileInfo, error) }); ok {
+		if st, err := stater.Stat(); err == nil {
+			prog.SetTotal(uint64(st.Size()))
+		}
+	}
+	if err := target.StreamTo(ctx, stream, io.TeeReader(reader, &progress.Writer{})); err != nil {
+		return fmt.Errorf("updating %s: %w", logStr, err)
+	}
+	duration := time.Since(start)
+	transferred := progress.Reset()
+	log.Printf("\rTransferred %s (%s) at %.2f MiB/s (total: %v)",
+		logStr,
+		humanize.Bytes(transferred),
+		float64(transferred)/duration.Seconds()/1024/1024,
+		duration.Round(time.Second))
+
+	return nil
+}

internal/packer/packerwrite.go

@@ -0,0 +1,433 @@
+package packer
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"path/filepath"
+	"runtime/trace"
+	"strings"
+
+	"github.com/gokrazy/internal/config"
+	"github.com/gokrazy/internal/deviceconfig"
+	"github.com/gokrazy/internal/httpclient"
+	"github.com/gokrazy/internal/updateflag"
+	"github.com/gokrazy/tools/packer"
+	"github.com/gokrazy/updater"
+)
+
+func (pack *Pack) logicWrite(dnsCheck chan error) error {
+	ctx := context.Background()
+	log := pack.Env.Logger()
+
+	var (
+		updateHttpClient *http.Client
+		updateBaseUrl    *url.URL
+		target           *updater.Target
+	)
+
+	newInstallation := pack.Cfg.InternalCompatibilityFlags.Update == ""
+	insecure := pack.Cfg.InternalCompatibilityFlags.Insecure
+	if !newInstallation {
+		update := pack.update // for convenience
+		var err error
+		updateBaseUrl, err = updateflag.Value{
+			Update: pack.Cfg.InternalCompatibilityFlags.Update,
+		}.BaseURL(update.HTTPPort, update.HTTPSPort, pack.schema, update.Hostname, update.HTTPPassword)
+		if err != nil {
+			return err
+		}
+
+		updateHttpClient, _, err = httpclient.GetTLSHttpClientByTLSFlag(update.UseTLS, insecure, updateBaseUrl)
+		if err != nil {
+			return fmt.Errorf("getting http client by tls flag: %v", err)
+		}
+
+		updateBaseUrl.Path = "/"
+
+		target, err = updater.NewTarget(ctx, updateBaseUrl.String(), updateHttpClient)
+		if err != nil {
+			if !insecure {
+				return fmt.Errorf("checking target partuuid support: %v", err)
+			}
+			log.Printf("Falling back to HTTP because of the --insecure flag")
+			updateBaseUrl, err = updateflag.Value{
+				Update: pack.Cfg.InternalCompatibilityFlags.Update,
+			}.BaseURL(update.HTTPPort, update.HTTPSPort, "http", update.Hostname, update.HTTPPassword)
+			if err != nil {
+				return err
+			}
+
+			updateHttpClient, _, err = httpclient.GetTLSHttpClientByTLSFlag(update.UseTLS, insecure, updateBaseUrl)
+			if err != nil {
+				return fmt.Errorf("getting http client by tls flag: %v", err)
+			}
+			target, err = updater.NewTarget(ctx, updateBaseUrl.String(), updateHttpClient)
+			if err != nil {
+				return fmt.Errorf("checking target partuuid support: %v", err)
+			}
+		}
+		pack.UsePartuuid = target.Supports("partuuid")
+		pack.UseGPTPartuuid = target.Supports("gpt")
+		pack.UseGPT = target.Supports("gpt")
+		pack.ExistingEEPROM = target.InstalledEEPROM()
+	}
+	log.Printf("")
+	log.Printf("Feature summary:")
+	log.Printf("  use GPT: %v", pack.UseGPT)
+	log.Printf("  use PARTUUID: %v", pack.UsePartuuid)
+	log.Printf("  use GPT PARTUUID: %v", pack.UseGPTPartuuid)
+
+	cfg := pack.Cfg   // for convenience
+	root := pack.root // for convenience
+	// Determine where to write the boot and root images to.
+	var (
+		isDev                    bool
+		tmpBoot, tmpRoot, tmpMBR *os.File
+		bootSize, rootSize       int64
+	)
+	switch {
+	case cfg.InternalCompatibilityFlags.Overwrite != "" ||
+		(pack.Output != nil && pack.Output.Type == OutputTypeFull && pack.Output.Path != ""):
+
+		st, err := os.Stat(cfg.InternalCompatibilityFlags.Overwrite)
+		if err != nil && !os.IsNotExist(err) {
+			return err
+		}
+
+		isDev = err == nil && st.Mode()&os.ModeDevice == os.ModeDevice
+
+		if isDev {
+			if err := pack.overwriteDevice(cfg.InternalCompatibilityFlags.Overwrite, root, pack.rootDeviceFiles); err != nil {
+				return err
+			}
+			log.Printf("To boot gokrazy, plug the SD card into a supported device (see https://gokrazy.org/platforms/)")
+			log.Printf("")
+		} else {
+			lower := 1200*MB + int(pack.firstPartitionOffsetSectors)
+
+			if cfg.InternalCompatibilityFlags.TargetStorageBytes == 0 {
+				return fmt.Errorf("--target_storage_bytes is required (e.g. --target_storage_bytes=%d) when using overwrite with a file", lower)
+			}
+			if cfg.InternalCompatibilityFlags.TargetStorageBytes%512 != 0 {
+				return fmt.Errorf("--target_storage_bytes must be a multiple of 512 (sector size), use e.g. %d", lower)
+			}
+			if cfg.InternalCompatibilityFlags.TargetStorageBytes < lower {
+				return fmt.Errorf("--target_storage_bytes must be at least %d (for boot + 2 root file systems + 100 MB /perm)", lower)
+			}
+
+			bootSize, rootSize, err = pack.overwriteFile(root, pack.rootDeviceFiles, pack.firstPartitionOffsetSectors)
+			if err != nil {
+				return err
+			}
+
+			log.Printf("To boot gokrazy, copy %s to an SD card and plug it into a supported device (see https://gokrazy.org/platforms/)", cfg.InternalCompatibilityFlags.Overwrite)
+			log.Printf("")
+		}
+
+	case pack.Output != nil && pack.Output.Type == OutputTypeGaf && pack.Output.Path != "":
+		if err := pack.overwriteGaf(root, pack.sbom); err != nil {
+			return err
+		}
+
+	default:
+		if cfg.InternalCompatibilityFlags.OverwriteBoot != "" {
+			mbrfn := cfg.InternalCompatibilityFlags.OverwriteMBR
+			if cfg.InternalCompatibilityFlags.OverwriteMBR == "" {
+				var err error
+				tmpMBR, err = os.CreateTemp("", "gokrazy")
+				if err != nil {
+					return err
+				}
+				defer os.Remove(tmpMBR.Name())
+				mbrfn = tmpMBR.Name()
+			}
+			if err := pack.writeBootFile(cfg.InternalCompatibilityFlags.OverwriteBoot, mbrfn); err != nil {
+				return err
+			}
+		}
+
+		if cfg.InternalCompatibilityFlags.OverwriteRoot != "" {
+			var rootErr error
+			trace.WithRegion(context.Background(), "writeroot", func() {
+				rootErr = pack.writeRootFile(cfg.InternalCompatibilityFlags.OverwriteRoot, root)
+			})
+			if rootErr != nil {
+				return rootErr
+			}
+		}
+
+		if cfg.InternalCompatibilityFlags.OverwriteBoot == "" && cfg.InternalCompatibilityFlags.OverwriteRoot == "" {
+			var err error
+			tmpMBR, err = os.CreateTemp("", "gokrazy")
+			if err != nil {
+				return err
+			}
+			defer os.Remove(tmpMBR.Name())
+
+			tmpBoot, err = os.CreateTemp("", "gokrazy")
+			if err != nil {
+				return err
+			}
+			defer os.Remove(tmpBoot.Name())
+
+			if err := pack.writeBoot(tmpBoot, tmpMBR.Name()); err != nil {
+				return err
+			}
+
+			tmpRoot, err = os.CreateTemp("", "gokrazy")
+			if err != nil {
+				return err
+			}
+			defer os.Remove(tmpRoot.Name())
+
+			if err := pack.writeRoot(tmpRoot, root); err != nil {
+				return err
+			}
+		}
+	}
+
+	log.Printf("")
+	log.Printf("Build complete!")
+
+	if err := pack.printHowToInteract(cfg); err != nil {
+		return err
+	}
+
+	if err := <-dnsCheck; err != nil {
+		log.Printf("WARNING: if the above URL does not work, perhaps name resolution (DNS) is broken")
+		log.Printf("in your local network? Resolving your hostname failed: %v", err)
+		log.Printf("Did you maybe configure a DNS server other than your router?")
+		log.Printf("")
+	}
+
+	if newInstallation {
+		return nil
+	}
+
+	return pack.logicUpdate(ctx, isDev, bootSize, rootSize, tmpMBR, tmpBoot, tmpRoot, updateBaseUrl, target, updateHttpClient)
+}
+
+func (p *Pack) overwriteDevice(dev string, root *FileInfo, rootDeviceFiles []deviceconfig.RootFile) error {
+	log := p.Env.Logger()
+
+	if err := verifyNotMounted(dev); err != nil {
+		return err
+	}
+	parttable := "GPT + Hybrid MBR"
+	if !p.UseGPT {
+		parttable = "no GPT, only MBR"
+	}
+	log.Printf("partitioning %s (%s)", dev, parttable)
+
+	f, err := p.partition(p.Cfg.InternalCompatibilityFlags.Overwrite)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	if _, err := f.Seek(p.FirstPartitionOffsetSectors*512, io.SeekStart); err != nil {
+		return err
+	}
+
+	if err := p.writeBoot(f, ""); err != nil {
+		return err
+	}
+
+	if err := p.writeMBR(p.FirstPartitionOffsetSectors, &offsetReadSeeker{f, p.FirstPartitionOffsetSectors * 512}, f, p.Partuuid); err != nil {
+		return err
+	}
+
+	if _, err := f.Seek((p.FirstPartitionOffsetSectors+(100*MB/512))*512, io.SeekStart); err != nil {
+		return err
+	}
+
+	tmp, err := os.CreateTemp("", "gokr-packer")
+	if err != nil {
+		return err
+	}
+	defer os.Remove(tmp.Name())
+	defer tmp.Close()
+
+	if err := p.writeRoot(tmp, root); err != nil {
+		return err
+	}
+	if _, err := tmp.Seek(0, io.SeekStart); err != nil {
+		return err
+	}
+
+	if _, err := io.Copy(f, tmp); err != nil {
+		return err
+	}
+
+	if err := p.writeRootDeviceFiles(f, rootDeviceFiles); err != nil {
+		return err
+	}
+
+	if err := f.Close(); err != nil {
+		return err
+	}
+
+	log.Printf("If your applications need to store persistent data, unplug and re-plug the SD card, then create a file system using e.g.:")
+	log.Printf("")
+	partition := partitionPath(dev, "4")
+	if p.ModifyCmdlineRoot() {
+		partition = fmt.Sprintf("/dev/disk/by-partuuid/%s", p.PermUUID())
+	} else {
+		if target, err := filepath.EvalSymlinks(dev); err == nil {
+			partition = partitionPath(target, "4")
+		}
+	}
+	log.Printf("\tmkfs.ext4 %s", partition)
+	log.Printf("")
+
+	return nil
+}
+
+func partitionPath(base, num string) string {
+	if strings.HasPrefix(base, "/dev/mmcblk") ||
+		strings.HasPrefix(base, "/dev/loop") {
+		return base + "p" + num
+	} else if strings.HasPrefix(base, "/dev/disk") ||
+		strings.HasPrefix(base, "/dev/rdisk") {
+		return base + "s" + num
+	}
+	return base + num
+}
+
+type offsetReadSeeker struct {
+	io.ReadSeeker
+	offset int64
+}
+
+func (ors *offsetReadSeeker) Seek(offset int64, whence int) (int64, error) {
+	if whence == io.SeekStart {
+		// github.com/gokrazy/internal/fat.Reader only uses io.SeekStart
+		return ors.ReadSeeker.Seek(offset+ors.offset, io.SeekStart)
+	}
+	return ors.ReadSeeker.Seek(offset, whence)
+}
+
+type countingWriter int64
+
+func (cw *countingWriter) Write(p []byte) (n int, err error) {
+	*cw += countingWriter(len(p))
+	return len(p), nil
+}
+
+func (p *Pack) overwriteFile(root *FileInfo, rootDeviceFiles []deviceconfig.RootFile, firstPartitionOffsetSectors int64) (bootSize int64, rootSize int64, err error) {
+	log := p.Env.Logger()
+
+	f, err := os.Create(p.Cfg.InternalCompatibilityFlags.Overwrite)
+	if err != nil {
+		return 0, 0, err
+	}
+
+	if err := f.Truncate(int64(p.Cfg.InternalCompatibilityFlags.TargetStorageBytes)); err != nil {
+		return 0, 0, err
+	}
+
+	if err := p.Partition(f, uint64(p.Cfg.InternalCompatibilityFlags.TargetStorageBytes)); err != nil {
+		return 0, 0, err
+	}
+
+	if _, err := f.Seek(p.FirstPartitionOffsetSectors*512, io.SeekStart); err != nil {
+		return 0, 0, err
+	}
+	var bs countingWriter
+	if err := p.writeBoot(io.MultiWriter(f, &bs), ""); err != nil {
+		return 0, 0, err
+	}
+
+	if err := p.writeMBR(p.FirstPartitionOffsetSectors, &offsetReadSeeker{f, p.FirstPartitionOffsetSectors * 512}, f, p.Partuuid); err != nil {
+		return 0, 0, err
+	}
+
+	if _, err := f.Seek(p.FirstPartitionOffsetSectors*512+100*MB, io.SeekStart); err != nil {
+		return 0, 0, err
+	}
+
+	tmp, err := os.CreateTemp("", "gokr-packer")
+	if err != nil {
+		return 0, 0, err
+	}
+	defer os.Remove(tmp.Name())
+	defer tmp.Close()
+
+	if err := p.writeRoot(tmp, root); err != nil {
+		return 0, 0, err
+	}
+	if _, err := tmp.Seek(0, io.SeekStart); err != nil {
+		return 0, 0, err
+	}
+
+	var rs countingWriter
+	if _, err := io.Copy(io.MultiWriter(f, &rs), tmp); err != nil {
+		return 0, 0, err
+	}
+
+	if err := p.writeRootDeviceFiles(f, rootDeviceFiles); err != nil {
+		return 0, 0, err
+	}
+
+	log.Printf("If your applications need to store persistent data, create a file system using e.g.:")
+	log.Printf("\t/sbin/mkfs.ext4 -F -E offset=%v %s %v", p.FirstPartitionOffsetSectors*512+1100*MB, p.Cfg.InternalCompatibilityFlags.Overwrite, packer.PermSizeInKB(firstPartitionOffsetSectors, uint64(p.Cfg.InternalCompatibilityFlags.TargetStorageBytes)))
+	log.Printf("")
+
+	return int64(bs), int64(rs), f.Close()
+}
+
+func (pack *Pack) printHowToInteract(cfg *config.Struct) error {
+	log := pack.Env.Logger()
+	update := pack.update // for convenience
+
+	updateFlag := pack.Cfg.InternalCompatibilityFlags.Update
+	if updateFlag == "" {
+		updateFlag = "yes"
+	}
+	updateBaseUrl, err := updateflag.Value{
+		Update: updateFlag,
+	}.BaseURL(update.HTTPPort, update.HTTPSPort, pack.schema, update.Hostname, update.HTTPPassword)
+	if err != nil {
+		return err
+	}
+
+	log.Printf("")
+	log.Printf("To interact with the device, gokrazy provides a web interface reachable at:")
+	log.Printf("")
+	log.Printf("\t%s", updateBaseUrl.String())
+	log.Printf("")
+	log.Printf("In addition, the following Linux consoles are set up:")
+	log.Printf("")
+	if cfg.SerialConsoleOrDefault() != "disabled" {
+		log.Printf("\t1. foreground Linux console on the serial port (115200n8, pin 6, 8, 10 for GND, TX, RX), accepting input")
+		log.Printf("\t2. secondary Linux framebuffer console on HDMI; shows Linux kernel message but no init system messages")
+	} else {
+		log.Printf("\t1. foreground Linux framebuffer console on HDMI")
+	}
+
+	if cfg.SerialConsoleOrDefault() != "disabled" {
+		log.Printf("")
+		log.Printf("Use -serial_console=disabled to make gokrazy not touch the serial port, and instead make the framebuffer console on HDMI the foreground console")
+	}
+	log.Printf("")
+	if pack.schema == "https" {
+		certObj, err := getCertificateFromString(update.CertPEM)
+		if err != nil {
+			return fmt.Errorf("error loading certificate: %v", err)
+		} else {
+			log.Printf("")
+			log.Printf("The TLS Certificate of the gokrazy web interface is located under")
+			log.Printf("\t%s", cfg.Meta.Path)
+			log.Printf("The fingerprint of the Certificate is")
+			log.Printf("\t%x", getCertificateFingerprintSHA1(certObj))
+			log.Printf("The certificate is valid until")
+			log.Printf("\t%s", certObj.NotAfter.String())
+			log.Printf("Please verify the certificate, before adding an exception to your browser!")
+		}
+	}
+	return nil
+}

internal/packer/validatekernel.go

@@ -0,0 +1,82 @@
+package packer
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+
+	"github.com/gokrazy/tools/packer"
+)
+
+// kernelGoarch returns the GOARCH value that corresponds to the provided
+// vmlinuz header. It returns one of "arm", "arm64", "386", "amd64" or the empty
+// string if not detected.
+func kernelGoarch(hdr []byte) string {
+	// Some constants from the file(1) command's magic.
+	const (
+		// 32-bit arm: https://github.com/file/file/blob/65be1904/magic/Magdir/linux#L238-L241
+		arm32Magic       = 0x016f2818
+		arm32MagicOffset = 0x24
+		// 64-bit arm: https://github.com/file/file/blob/65be1904/magic/Magdir/linux#L253-L254
+		arm64Magic       = 0x644d5241
+		arm64MagicOffset = 0x38
+		// x86: https://github.com/file/file/blob/65be1904/magic/Magdir/linux#L137-L152
+		x86Magic            = 0xaa55
+		x86MagicOffset      = 0x1fe
+		x86XloadflagsOffset = 0x236
+	)
+	if len(hdr) >= arm64MagicOffset+4 && binary.LittleEndian.Uint32(hdr[arm64MagicOffset:]) == arm64Magic {
+		return "arm64"
+	}
+	if len(hdr) >= arm32MagicOffset+4 && binary.LittleEndian.Uint32(hdr[arm32MagicOffset:]) == arm32Magic {
+		return "arm"
+	}
+	if len(hdr) >= x86XloadflagsOffset+2 && binary.LittleEndian.Uint16(hdr[x86MagicOffset:]) == x86Magic {
+		// XLF0 in arch/x86/boot/header.S
+		if hdr[x86XloadflagsOffset]&1 != 0 {
+			return "amd64"
+		} else {
+			return "386"
+		}
+	}
+	return ""
+}
+
+// validateTargetArchMatchesKernel validates that the packer.TargetArch
+// corresponds to the kernel's architecture.
+//
+// See https://github.com/gokrazy/gokrazy/issues/191 for background. Maybe the
+// TargetArch will become automatic in the future but for now this is a safety
+// net to prevent people from bricking their appliances with the wrong userspace
+// architecture.
+func (pack *Pack) validateTargetArchMatchesKernel() error {
+	cfg := pack.Cfg
+	kernelDir, err := packer.PackageDir(cfg.KernelPackageOrDefault())
+	if err != nil {
+		return err
+	}
+	kernelPath := filepath.Join(kernelDir, "vmlinuz")
+	k, err := os.Open(kernelPath)
+	if err != nil {
+		return err
+	}
+	defer k.Close()
+	hdr := make([]byte, 1<<10) // plenty
+	if _, err := io.ReadFull(k, hdr); err != nil {
+		return err
+	}
+	kernelArch := kernelGoarch(hdr)
+	if kernelArch == "" {
+		return fmt.Errorf("kernel %v architecture in %s not detected", cfg.KernelPackageOrDefault(), kernelPath)
+	}
+	targetArch := packer.TargetArch()
+	if kernelArch != targetArch {
+		return fmt.Errorf("target architecture %q (GOARCH) doesn't match the %s kernel type %q",
+			targetArch,
+			cfg.KernelPackageOrDefault(),
+			kernelArch)
+	}
+	return nil
+}

internal/packer/write.go

@@ -48,7 +48,7 @@ func copyFile(fw *fat.Writer, dest string, src fs.File, srcName string) error {
 	return src.Close()
 }
 
-func copyFileSquash(d *squashfs.Directory, dest, src string) error {
+func copyFileSquash(d *squashfs.Directory, dest, src string, xattrs map[string][]byte) error {
 	f, err := os.Open(src)
 	if err != nil {
 		return err
@@ -58,7 +58,7 @@ func copyFileSquash(d *squashfs.Directory, dest, src string) error {
 	if err != nil {
 		return err
 	}
-	w, err := d.File(filepath.Base(dest), st.ModTime(), st.Mode()&os.ModePerm)
+	w, err := d.File(filepath.Base(dest), st.ModTime(), st.Mode()&os.ModePerm, xattrs)
 	if err != nil {
 		return err
 	}
@@ -202,6 +202,18 @@ func (p *Pack) copyGlobsToBoot(fw *fat.Writer, srcDir string, globs []string) er
 	return nil
 }
 
+func (p *Pack) writeBootFile(bootfilename, mbrfilename string) error {
+	f, err := os.Create(bootfilename)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	if err := p.writeBoot(f, mbrfilename); err != nil {
+		return err
+	}
+	return f.Close()
+}
+
 func (p *Pack) writeBoot(f io.Writer, mbrfilename string) error {
 	log := p.Env.Logger()
 	log.Printf("")
@@ -254,39 +266,25 @@ func (p *Pack) writeBoot(f io.Writer, mbrfilename string) error {
 		}
 	}
 
-	// EEPROM update procedure. See also:
-	// https://news.ycombinator.com/item?id=21674550
-	writeEepromUpdateFile := func(globPattern, target string) (sig string, _ error) {
-		matches, err := filepath.Glob(globPattern)
-		if err != nil {
-			return "", err
-		}
-		if len(matches) == 0 {
-			return "", fmt.Errorf("invalid -eeprom_package: no files matching %s", filepath.Base(globPattern))
-		}
-
+	// matches must be non-empty
+	bestMatch := func(matches []string) string {
 		// Select the EEPROM file that sorts last.
 		// This corresponds to most recent for the pieeprom-*.bin files,
 		// which contain the date in yyyy-mm-dd format.
 		sort.Sort(sort.Reverse(sort.StringSlice(matches)))
-
-		f, err := os.Open(matches[0])
-		if err != nil {
-			return "", err
-		}
-		defer f.Close()
-		st, err := f.Stat()
-		if err != nil {
-			return "", err
-		}
+		return matches[0]
+	}
+	// EEPROM update procedure. See also:
+	// https://news.ycombinator.com/item?id=21674550
+	writeEepromUpdate := func(target string, modTime time.Time, r io.Reader) (sig string, _ error) {
 		// Copy the EEPROM file into the image and calculate its SHA256 hash
 		// while doing so:
-		w, err := fw.File(target, st.ModTime())
+		w, err := fw.File(target, modTime)
 		if err != nil {
 			return "", err
 		}
 		h := sha256.New()
-		if _, err := io.Copy(w, io.TeeReader(f, h)); err != nil {
+		if _, err := io.Copy(w, io.TeeReader(r, h)); err != nil {
 			return "", err
 		}
 
@@ -301,33 +299,81 @@ func (p *Pack) writeBoot(f io.Writer, mbrfilename string) error {
 		sigFn := target
 		ext := filepath.Ext(sigFn)
 		if ext == "" {
-			return "", fmt.Errorf("BUG: cannot derive signature file name from matches[0]=%q", matches[0])
+			return "", fmt.Errorf("BUG: cannot derive signature file name from target=%q", target)
 		}
 		sigFn = strings.TrimSuffix(sigFn, ext) + ".sig"
-		w, err = fw.File(sigFn, st.ModTime())
+		w, err = fw.File(sigFn, modTime)
 		if err != nil {
 			return "", err
 		}
 		_, err = fmt.Fprintf(w, "%x\n", h.Sum(nil))
+		if err != nil {
+			return "", err
+		}
+		_, err = fmt.Fprintf(w, "ts: %d\n", modTime.Unix())
 		return fmt.Sprintf("%x", h.Sum(nil)), err
 	}
+	writeEepromUpdateFile := func(matches []string, target string) (sig string, _ error) {
+		f, err := os.Open(bestMatch(matches))
+		if err != nil {
+			return "", err
+		}
+		defer f.Close()
+		st, err := f.Stat()
+		if err != nil {
+			return "", err
+		}
+		return writeEepromUpdate(target, st.ModTime(), f)
+	}
+
+	var pieSig string
 	if eepromDir != "" {
+		log.Printf("EEPROM directory: %s", eepromDir)
+		log.Printf("(gokrazy config mtime: %v)", p.Cfg.Meta.LastModified)
 		log.Printf("EEPROM update summary:")
-		pieSig, err := writeEepromUpdateFile(filepath.Join(eepromDir, "pieeprom-*.bin"), "/pieeprom.upd")
+		eepromGlob := filepath.Join(eepromDir, "pieeprom-*.bin")
+		eepromMatches, err := filepath.Glob(eepromGlob)
 		if err != nil {
 			return err
 		}
-		vlSig, err := writeEepromUpdateFile(filepath.Join(eepromDir, "vl805-*.bin"), "/vl805.bin")
+		if len(eepromMatches) == 0 {
+			return fmt.Errorf("invalid -eeprom_package: no files matching %s", filepath.Base(eepromGlob))
+		}
+		if ee := p.Cfg.BootloaderExtraEEPROM; len(ee) > 0 {
+			updated, err := applyExtraEEPROM(bestMatch(eepromMatches), ee)
+			if err != nil {
+				return err
+			}
+			pieSig, err = writeEepromUpdate("/pieeprom.upd", p.Cfg.Meta.LastModified, bytes.NewReader(updated))
+			if err != nil {
+				return err
+			}
+		} else {
+			pieSig, err = writeEepromUpdateFile(eepromMatches, "/pieeprom.upd")
+			if err != nil {
+				return err
+			}
+		}
+
+		vl805Glob := filepath.Join(eepromDir, "vl805-*.bin")
+		vl805Matches, err := filepath.Glob(vl805Glob)
 		if err != nil {
 			return err
 		}
+		var vlSig string
+		if len(vl805Matches) > 0 {
+			vlSig, err = writeEepromUpdateFile(vl805Matches, "/vl805.bin")
+			if err != nil {
+				return err
+			}
+		}
 		targetFilename := "/recovery.bin"
 		if pieSig == p.ExistingEEPROM.PieepromSHA256 &&
 			vlSig == p.ExistingEEPROM.VL805SHA256 {
 			log.Printf("  installing recovery.bin as RECOVERY.000 (EEPROM already up-to-date)")
 			targetFilename = "/RECOVERY.000"
 		}
-		if _, err := writeEepromUpdateFile(filepath.Join(eepromDir, "recovery.bin"), targetFilename); err != nil {
+		if _, err := writeEepromUpdateFile([]string{filepath.Join(eepromDir, "recovery.bin")}, targetFilename); err != nil {
 			return err
 		}
 	}
@@ -397,6 +443,7 @@ type FileInfo struct {
 	FromHost    string
 	FromLiteral string
 	SymlinkDest string
+	Xattrs      map[string][]byte
 
 	Dirents []*FileInfo
 }
@@ -459,12 +506,79 @@ func (fi *FileInfo) mustFindDirent(path string) *FileInfo {
 	return nil
 }
 
+func addToFileInfo(parent *FileInfo, path string) (time.Time, error) {
+	entries, err := os.ReadDir(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return time.Time{}, nil
+		}
+		return time.Time{}, err
+	}
+
+	var latestTime time.Time
+	for _, entry := range entries {
+		filename := entry.Name()
+		// get existing file info
+		var fi *FileInfo
+		for _, ent := range parent.Dirents {
+			if ent.Filename == filename {
+				fi = ent
+				break
+			}
+		}
+
+		info, err := entry.Info()
+		if err != nil {
+			return time.Time{}, err
+		}
+		if info.Mode()&os.ModeSymlink != 0 {
+			info, err = os.Stat(filepath.Join(path, filename))
+			if err != nil {
+				return time.Time{}, err
+			}
+		}
+
+		if latestTime.Before(info.ModTime()) {
+			latestTime = info.ModTime()
+		}
+
+		// or create if not exist
+		if fi == nil {
+			fi = &FileInfo{
+				Filename: filename,
+				Mode:     info.Mode(),
+			}
+			parent.Dirents = append(parent.Dirents, fi)
+		} else {
+			// file overwrite is not supported -> return error
+			if !info.IsDir() || fi.FromHost != "" || fi.FromLiteral != "" {
+				return time.Time{}, fmt.Errorf("file already exists in filesystem: %s", filepath.Join(path, filename))
+			}
+		}
+
+		// add content
+		if info.IsDir() {
+			modTime, err := addToFileInfo(fi, filepath.Join(path, filename))
+			if err != nil {
+				return time.Time{}, err
+			}
+			if latestTime.Before(modTime) {
+				latestTime = modTime
+			}
+		} else {
+			fi.FromHost = filepath.Join(path, filename)
+		}
+	}
+
+	return latestTime, nil
+}
+
 type foundBin struct {
 	gokrazyPath string
 	hostPath    string
 }
 
-func findBins(cfg *config.Struct, buildEnv *packer.BuildEnv, bindir string, basenames map[string]string) (*FileInfo, []foundBin, error) {
+func findBins(cfg *config.Struct, buildEnv *packer.BuildEnv, bindir string, basenames map[string]string, xattrs map[string]map[string][]byte) (*FileInfo, []foundBin, error) {
 	var found []foundBin
 	result := FileInfo{Filename: ""}
 
@@ -519,15 +633,20 @@ func findBins(cfg *config.Struct, buildEnv *packer.BuildEnv, bindir string, base
 	}
 	user := FileInfo{Filename: "user"}
 	for _, pkg := range mainPkgs {
+		xattr := make(map[string][]byte)
 		basename := pkg.Basename()
 		if basenameOverride, ok := basenames[pkg.ImportPath]; ok {
 			basename = basenameOverride
 		}
+		if xattrsOverride, ok := xattrs[pkg.ImportPath]; ok {
+			xattr = xattrsOverride
+		}
 		binPath := filepath.Join(bindir, basename)
 		fileIsELFOrFatal(binPath)
 		user.Dirents = append(user.Dirents, &FileInfo{
 			Filename: basename,
 			FromHost: binPath,
+			Xattrs:   xattr,
 		})
 		found = append(found, foundBin{
 			gokrazyPath: "/user/" + basename,
@@ -540,14 +659,14 @@ func findBins(cfg *config.Struct, buildEnv *packer.BuildEnv, bindir string, base
 
 func writeFileInfo(dir *squashfs.Directory, fi *FileInfo) error {
 	if fi.FromHost != "" { // copy a regular file
-		return copyFileSquash(dir, fi.Filename, fi.FromHost)
+		return copyFileSquash(dir, fi.Filename, fi.FromHost, fi.Xattrs)
 	}
 	if fi.FromLiteral != "" { // write a regular file
 		mode := fi.Mode
 		if mode == 0 {
 			mode = 0444
 		}
-		w, err := dir.File(fi.Filename, time.Now(), mode)
+		w, err := dir.File(fi.Filename, time.Now(), mode, fi.Xattrs)
 		if err != nil {
 			return err
 		}
@@ -578,6 +697,18 @@ func writeFileInfo(dir *squashfs.Directory, fi *FileInfo) error {
 	return d.Flush()
 }
 
+func (p *Pack) writeRootFile(filename string, root *FileInfo) error {
+	f, err := os.Create(filename)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	if err := p.writeRoot(f, root); err != nil {
+		return err
+	}
+	return f.Close()
+}
+
 func (p *Pack) writeRoot(f io.WriteSeeker, root *FileInfo) error {
 	log := p.Env.Logger()