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<title>s6-rc: the s6-rc-init program</title>
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<p>
<a href="index.html">s6-rc</a><br />
<a href="//skarnet.org/software/">Software</a><br />
<a href="//skarnet.org/">skarnet.org</a>
</p>
<h1> The s6-rc-init program </h1>
<p>
s6-rc-init is an initialization tool for the s6-rc
system. It must be run as root, at boot time, prior to any
invocation of the
<a href="s6-rc.html">s6-rc</a> binary.
</p>
<h2> Interface </h2>
<pre>
s6-rc-init [ -c <em>compiled</em> ] [ -l <em>live</em> ] [ -t <em>timeout</em> ] [ -b ] <em>scandir</em>
</pre>
<ul>
<li> <em>compiled</em> (if the <tt>-d</tt> option hasn't been given),
<em>live</em> and <em>scandir</em> must be absolute paths. </li>
<li> s6-rc-init expects to find a <em>compiled service database</em>
in <em>compiled</em>. It expects to be able to create a directory
named <em>live</em>. It also expects that an instance of
<a href="//skarnet.org/software/s6/s6-svscan.html">s6-svscan</a>
is running on <em>scandir</em>. </li>
<li> s6-rc-init initializes the live state in <em>live</em>. It
declares <em>compiled</em> as the current service database and
sets the state as "all services down". </li>
<li> It then copies verbatim all
the service directories declared by <em>compiled</em> into a
subdirectory of <em>live</em>, adds <tt>./down</tt> files to the live copies
and links those live copies into <em>scandir</em>. It then triggers
<a href="//skarnet.org/software/s6/s6-svscan.html">s6-svscan</a>,
which will pick up the new service directories and start
<a href="//skarnet.org/software/s6/s6-supervise.html">s6-supervise</a>
processes on them - but the service themselves will not be started
right away, because of the <tt>./down</tt> files. </li>
<li> s6-rc-init waits for all s6-supervise processes to be
operational, then exits 0. </li>
</ul>
<h2> Options </h2>
<ul>
<li> <tt>-t <em>timeout</em></tt> : if all
s6-supervise processes are not up and running after <em>timeout</em>
milliseconds, s6-rc-init will complain and exit 111. This is a
safety feature so s6-rc-init doesn't hang indefinitely on a
nonworking installation; normally this initialization should not take
more than a few milliseconds. </li>
<li> <tt>-c <em>compiled</em></tt> : declare <em>compiled</em>
as the current compiled service database for the upcoming live state.
Default is <tt>/etc/s6-rc/compiled</tt>. </li>
<li> <tt>-l <em>live</em></tt> : Store the live state into
the <em>live</em> directory, which should not exist prior to running
s6-rc-init, but should be under a writable filesystem - likely a RAM
filesystem. Default is
<tt>/run/s6-rc</tt>. The default can be changed at compile time by
giving the <tt>--livedir=<em>live</em></tt> option to
<tt>./configure</tt>. </li>
<li> <tt>-b</tt> : blocking lock. If the database is currently
being used by another program, s6-rc-init will wait until that
other program has released its lock on the database, then proceed.
By default, s6-rc-init fails with an error message if the database
is currently in use. </li>
<li><tt>-d</tt> : dereference <em>compiled</em>. Fully resolve
the <em>compiled</em> path before declaring it as the current
compiled service database for the upcoming live state. This allows
<em>compiled</em> to be a symlink that can be updated later without
impacting the current live state. Using this flag in your init scripts'
<tt>s6-rc-init</tt> invocation means that it's possible to boot on a
compiled service database whose validity has not previously been
guaranteed by a successful <a href="s6-rc-update.html">s6-rc-update</a>
invocation: you should know what you are doing. </li>
</ul>
<h2> Typical usage </h2>
<p>
Administrators should invoke <tt>s6-rc-init</tt> once, in their
early boot scripts, after s6-svscan is functional and ready to
supervise longrun services (and after its catch-all logger, if
any, has started), but before any
other initialization. (The rest of the initialization can be
written as a set of s6-rc services, and performed by just one
invocation of the <a href="s6-rc.html">s6-rc change</a> command.)
</p>
<p>
For instance, when using an init created by
<a href="//skarnet.org/software/s6-linux-init/">s6-linux-init</a>,
<tt>s6-rc-init</tt> should be the first command in the
<em>stage2</em> (by default <tt>/etc/rc.init</tt>) script.
</p>
<h2> Notes </h2>
<ul>
<li> The directory created by s6-rc-init will actually be called
<em>live</em><tt>:initial</tt>, and <em>live</em> will be a symbolic
link to that directory. Users should ignore this, and always refer
to the live directory as <em>live</em> in their future
<a href="s6-rc.html">s6-rc</a> or <a href="s6-rc-update.html">s6-rc-update</a>
invocations. The reason for this behaviour is that
<a href="s6-rc-update.html">s6-rc-update</a> creates another,
similarly named, directory (<em>live</em><tt>:<em>suffix</em></tt>)
and updates the live state by atomically changing the target of the
<em>live</em> symlink - so <em>live</em> will not change names, whereas
the real directory may.) </li>
<li> Similarly, it is recommended that administrators store their
compiled service databases into some versioned directory, and that
<em>compiled</em> be a symbolic link to the database currently in
use. This will make it easier to create new compiled databases and
switch them with <a href="s6-rc-update.html">s6-rc-update</a>
without having to change the s6-rc-init invocation in boot scripts. </li>
<li> After s6-rc-init runs, <em>compiled</em> has become the
"live compiled database", and must not be tampered with or deleted.
The only way to free it for deletion is to replace it with another
database, via a call to <a href="s6-rc-update.html">s6-rc-update</a>. </li>
</ul>
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