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<meta name="description" content="Process supervision Tip You can find the corresponding code in func gokrazy.supervise.
gokrazy’s init process (pid 1) supervises all the binaries the user specified via gokr-packer flags.
More specifically, gokrazy:
Starts your binary using Go’s os/exec.Command API. The stdout and stderr file descriptors are hooked up to a ring buffer and can be viewed via gokrazy’s web interface. Extra command-line flags or environment variables can be specified using per-package configuration. When your binary’s process exits, gokrazy restarts it! If the process exits with status code 0 (or 125), gokrazy will stop supervision. Exiting immediately with status code 0 when the GOKRAZY_FIRST_START=1 environment variable is set means “don’t start the program on boot” Environment variables gokrazy sets the HOME environment variable to HOME=/perm/home/&lt;cmd&gt;, where &lt;cmd&gt; is the name of your binary. For example, tailscale.com/cmd/tailscaled is started with HOME=/perm/home/tailscaled.">
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<meta name="twitter:description" content="Process supervision Tip You can find the corresponding code in func gokrazy.supervise.
gokrazy’s init process (pid 1) supervises all the binaries the user specified via gokr-packer flags.
More specifically, gokrazy:
Starts your binary using Go’s os/exec.Command API. The stdout and stderr file descriptors are hooked up to a ring buffer and can be viewed via gokrazy’s web interface. Extra command-line flags or environment variables can be specified using per-package configuration. When your binary’s process exits, gokrazy restarts it! If the process exits with status code 0 (or 125), gokrazy will stop supervision. Exiting immediately with status code 0 when the GOKRAZY_FIRST_START=1 environment variable is set means “don’t start the program on boot” Environment variables gokrazy sets the HOME environment variable to HOME=/perm/home/&lt;cmd&gt;, where &lt;cmd&gt; is the name of your binary. For example, tailscale.com/cmd/tailscaled is started with HOME=/perm/home/tailscaled.">
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<meta property="og:description" content="Process supervision Tip You can find the corresponding code in func gokrazy.supervise.
gokrazy’s init process (pid 1) supervises all the binaries the user specified via gokr-packer flags.
More specifically, gokrazy:
Starts your binary using Go’s os/exec.Command API. The stdout and stderr file descriptors are hooked up to a ring buffer and can be viewed via gokrazy’s web interface. Extra command-line flags or environment variables can be specified using per-package configuration. When your binary’s process exits, gokrazy restarts it! If the process exits with status code 0 (or 125), gokrazy will stop supervision. Exiting immediately with status code 0 when the GOKRAZY_FIRST_START=1 environment variable is set means “don’t start the program on boot” Environment variables gokrazy sets the HOME environment variable to HOME=/perm/home/&lt;cmd&gt;, where &lt;cmd&gt; is the name of your binary. For example, tailscale.com/cmd/tailscaled is started with HOME=/perm/home/tailscaled.">
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<meta itemprop="description" content="Process supervision Tip You can find the corresponding code in func gokrazy.supervise.
gokrazy’s init process (pid 1) supervises all the binaries the user specified via gokr-packer flags.
More specifically, gokrazy:
Starts your binary using Go’s os/exec.Command API. The stdout and stderr file descriptors are hooked up to a ring buffer and can be viewed via gokrazy’s web interface. Extra command-line flags or environment variables can be specified using per-package configuration. When your binary’s process exits, gokrazy restarts it! If the process exits with status code 0 (or 125), gokrazy will stop supervision. Exiting immediately with status code 0 when the GOKRAZY_FIRST_START=1 environment variable is set means “don’t start the program on boot” Environment variables gokrazy sets the HOME environment variable to HOME=/perm/home/&lt;cmd&gt;, where &lt;cmd&gt; is the name of your binary. For example, tailscale.com/cmd/tailscaled is started with HOME=/perm/home/tailscaled.">
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<li><a href="#process-supervision">Process supervision</a></li>
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<h1 id="process-interface--requirements">Process interface / requirements</h1>
<h2 id="process-supervision">Process supervision<span class="btn cstyle anchor copyanchor scrollanchor link noborder notitle interactive"><button type="button" title="Copy link to clipboard"><i class="fa-fw fas fa-link fa-lg"></i></button></span></h2>
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Tip
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<p>You can find the corresponding code in
<a href="https://sourcegraph.com/search?q=context:global+repo:%5Egithub%5C.com/gokrazy/gokrazy%24+type:symbol+%5Esupervise%24&patternType=regexp&case=yes" rel="external">func gokrazy.supervise</a>.</p>
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</details>
<p>gokrazy’s init process (pid 1) supervises all the binaries the user specified via <code>gokr-packer</code> flags.</p>
<p>More specifically, gokrazy:</p>
<ol>
<li>Starts your binary using Go’s <code>os/exec.Command</code> API.
<ul>
<li>The <code>stdout</code> and <code>stderr</code> file descriptors are hooked up to a ring buffer and can be viewed via gokrazy’s web interface.</li>
<li>Extra command-line flags or environment variables can be specified using
<a href="/userguide/package-config/index.html">per-package configuration</a>.</li>
</ul>
</li>
<li>When your binary’s process exits, gokrazy restarts it!
<ul>
<li>If the process exits with status code <code>0</code> (or <code>125</code>), gokrazy will stop
supervision. Exiting immediately with status code <code>0</code> when the
<code>GOKRAZY_FIRST_START=1</code> environment variable is set means “don’t start the
program on boot”</li>
</ul>
</li>
</ol>
<h2 id="environment-variables">Environment variables<span class="btn cstyle anchor copyanchor scrollanchor link noborder notitle interactive"><button type="button" title="Copy link to clipboard"><i class="fa-fw fas fa-link fa-lg"></i></button></span></h2>
<p>gokrazy sets the <code>HOME</code> environment variable to <code>HOME=/perm/home/&lt;cmd&gt;</code>, where
<code>&lt;cmd&gt;</code> is the name of your binary. For example, <code>tailscale.com/cmd/tailscaled</code>
is started with <code>HOME=/perm/home/tailscaled</code>.</p>
<p>When your binary is first started, gokrazy sets the <code>GOKRAZY_FIRST_START=1</code>
environment variable.</p>
<p>The <code>PATH</code> environment variable is set to <code>/user:/gokrazy</code> so that all binaries
on the system can be discovered.</p>
<h2 id="privilege-dropping--security">Privilege dropping / security<span class="btn cstyle anchor copyanchor scrollanchor link noborder notitle interactive"><button type="button" title="Copy link to clipboard"><i class="fa-fw fas fa-link fa-lg"></i></button></span></h2>
<p>An easy way to implement privilege dropping in Go is to re-execute the process
with <a href="https://pkg.go.dev/syscall#SysProcAttr" rel="external">syscall.SysProcAttr</a> fields
set. For example, this is how you would drop privileges to user <code>nobody</code>
(uid/gid 65534):</p>
<div class="highlight actionbar-wrapper wrap-code" dir="auto"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-go" data-lang="go"><span style="display:flex;"><span><span style="color:#75715e">// mustDropPrivileges re-executes the program in a child process,</span>
</span></span><span style="display:flex;"><span><span style="color:#75715e">// dropping root privileges to user nobody.</span>
</span></span><span style="display:flex;"><span><span style="color:#66d9ef">func</span> <span style="color:#a6e22e">mustDropPrivileges</span>() {
</span></span><span style="display:flex;"><span> <span style="color:#66d9ef">if</span> <span style="color:#a6e22e">os</span>.<span style="color:#a6e22e">Getenv</span>(<span style="color:#e6db74">&#34;NTP_PRIVILEGES_DROPPED&#34;</span>) <span style="color:#f92672">==</span> <span style="color:#e6db74">&#34;1&#34;</span> {
</span></span><span style="display:flex;"><span> <span style="color:#66d9ef">return</span>
</span></span><span style="display:flex;"><span> }
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span> <span style="color:#a6e22e">cmd</span> <span style="color:#f92672">:=</span> <span style="color:#a6e22e">exec</span>.<span style="color:#a6e22e">Command</span>(<span style="color:#a6e22e">os</span>.<span style="color:#a6e22e">Args</span>[<span style="color:#ae81ff">0</span>])
</span></span><span style="display:flex;"><span> <span style="color:#a6e22e">cmd</span>.<span style="color:#a6e22e">Env</span> = append(<span style="color:#a6e22e">os</span>.<span style="color:#a6e22e">Environ</span>(), <span style="color:#e6db74">&#34;NTP_PRIVILEGES_DROPPED=1&#34;</span>)
</span></span><span style="display:flex;"><span> <span style="color:#a6e22e">cmd</span>.<span style="color:#a6e22e">Stdout</span> = <span style="color:#a6e22e">os</span>.<span style="color:#a6e22e">Stdout</span>
</span></span><span style="display:flex;"><span> <span style="color:#a6e22e">cmd</span>.<span style="color:#a6e22e">Stderr</span> = <span style="color:#a6e22e">os</span>.<span style="color:#a6e22e">Stderr</span>
</span></span><span style="display:flex;"><span> <span style="color:#a6e22e">cmd</span>.<span style="color:#a6e22e">SysProcAttr</span> = <span style="color:#f92672">&amp;</span><span style="color:#a6e22e">syscall</span>.<span style="color:#a6e22e">SysProcAttr</span>{
</span></span><span style="display:flex;"><span> <span style="color:#a6e22e">Credential</span>: <span style="color:#f92672">&amp;</span><span style="color:#a6e22e">syscall</span>.<span style="color:#a6e22e">Credential</span>{
</span></span><span style="display:flex;"><span> <span style="color:#a6e22e">Uid</span>: <span style="color:#ae81ff">65534</span>,
</span></span><span style="display:flex;"><span> <span style="color:#a6e22e">Gid</span>: <span style="color:#ae81ff">65534</span>,
</span></span><span style="display:flex;"><span> },
</span></span><span style="display:flex;"><span> }
</span></span><span style="display:flex;"><span> <span style="color:#a6e22e">log</span>.<span style="color:#a6e22e">Fatal</span>(<span style="color:#a6e22e">cmd</span>.<span style="color:#a6e22e">Run</span>())
</span></span><span style="display:flex;"><span>}</span></span></code></pre></div>
<p>Examples:</p>
<ul>
<li><a href="https://sourcegraph.com/github.com/gokrazy/gokrazy/-/blob/cmd/ntp/privdrop.go" rel="external"><code>github.com/gokrazy/gokrazy/cmd/ntp</code></a>
is a rather involved example which retains the CAP_SYS_TIME capability in the
child process</li>
<li><a href="https://sourcegraph.com/github.com/gokrazy/rsync/-/blob/internal/maincmd/namespacing_linux.go" rel="external"><code>github.com/gokrazy/rsync</code></a> uses Linux
mount namespaces and constructs a file system with read-only bind mounts of
the configured rsync modules</li>
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