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<title>s6: the s6-svscanboot program</title>
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<p>
<a href="index.html">s6</a><br />
<a href="//skarnet.org/software/">Software</a><br />
<a href="//skarnet.org/">www.skarnet.org</a>
</p>
<h1> The s6-svscanboot program </h1>
<p>
<tt>s6-svscanboot</tt> starts a supervision tree, spearheaded by
<a href="s6-svscan.html">s6-svscan</a>, while logging its own output,
as well as the output of the tree's <a href="s6-supervise.html">s6-supervise</a>
processes, into a catch-all logger that it itself supervises.
</p>
<p>
In other words, it starts a self-sufficient, self-contained supervision tree,
that does not leak logs &emdash; apart from exceptionally rare error messages
from the catch-all logger itself.
</p>
<p>
<tt>s6-svscanboot</tt> is meant to be used when an external service manager
needs to start an s6 supervision tree. It prevents the supervision tree's logs
from either flooding the upper service manager or being lost entirely.
</p>
<h2> Interface </h2>
<pre>
s6-svscanboot [ -c <em>devconsole</em> ] [ -D <em>catchalldir</em> ] [ -m <em>catchallmode</em> ] [ -l <em>catchalluser</em> ] [ -o <em>catchalloptions</em> ] [ -d <em>notif</em> ] [ -X <em>consoleholder</em> ] [ -C <em>services_max</em> ] [ -L <em>name_max</em> ] [ -t <em>rescan</em> ] <em>scandir</em>
</pre>
<ul>
<li> <tt>s6-svscanboot</tt> creates the <tt>/run/uncaught-logs</tt> directory
if it does not already exist, and changes its mode to 02750. </li>
<li> It creates the <em>scandir</em> directory if it does not exist yet.
<li> It deletes any pre-existing <tt><em>scandir</em>/s6-svscan-log</tt>
directory, then recreates it as a suitable
<a href="servicedir.html">service directory</a> running
<a href="s6-log.html">s6-log</a> to log to <tt>/run/uncaught-logs</tt>. This
is the service that will serve as the catch-all logger. </li>
<li> It redirects its standard input to <tt>/dev/null</tt>, and its standard
output and error to a named pipe that will be read by the catch-all logger.
It performs the necessary magic so that the redirection happens even though
that named pipe has no reader yet. </li>
<li> It execs into <a href="s6-svscan.html">s6-svscan</a>, running on
<em>scandir</em>. </li>
</ul>
<h2> Exit codes </h2>
<dl>
<dt> 100 </dt> <dd> Wrong usage </dd>
<dt> 111 </dt> <dd> System call failure </dd>
</dl>
<p>
On success, <tt>s6-svscanboot</tt> does not exit, but execs into
<a href="s6-svscan.html">s6-svscan</a> instead, which is supposed to remain
running until the administrator decides to stop it or the machine shuts down.
</p>
<h2> Options </h2>
<dl>
<dt> <tt>-c <em>console</em></tt>, <tt>--console=<em>console</em></tt> </dt>
<dd> Send the catch-all logger's error messages to device <em>console</em>. These
will be the only error messages from the supervision tree that will not go into
the catch-all logger. By default, this device is whatever <tt>s6-svscanboot</tt>
stderr points to at invocation time. </dd>
<dt> <tt>-D <em>dir</em></tt>, <tt>--catchall-directory=<em>dir</em></tt> </dt>
<dd> The directory where the <a href="s6-log.html">s6-log</a> catch-all will write
and rotate the supervision tree's logs. Default is <strong><tt>/run/uncaught-logs</tt></strong>. </dd>
<dt> <tt>-m <em>mode</em></tt>, <tt>--catchall-mode=<em>mode</em></tt> <dt>
<dd> What permissions the catch-all directory shall have. Default is <strong>02750</strong>. </dd>
<dt> <tt>-l <em>user</em></tt>, <tt>--catchall-user=<em>user</em></tt> <dt>
<dd> What user the catch-all logger shall run as. Default is the same user as
the supervision tree, i.e. the user that launched <tt>s6-svscanboot</tt>. This
option should only be used by root. </dd>
<dt> <tt>-o <em>options</em></tt>, <tt>--catchall-options=<em>options</em></tt> <dt>
<dd> What control and selection directives the <a href="s6-log.html">s6-log</a> program
shall use for logging its input. Directives should be separated by spaces. The
<em>options</em> string will appear verbatim in the <tt><em>scandir</em>/s6-svscan-log/run</tt>
script, so caution should be used when using this option. Default is <strong><tt>t</tt></strong>. </dd>
<dt> <tt>-d <em>notif</em></tt>, <tt>--notification-fd=<em>notif</em></tt> </dt>
<dd> Notify file descriptor <em>notif</em> when <a href="s6-svscan.html">s6-svscan</a> is ready.
This option is passed directly to <a href="s6-svscan.html">s6-svscan</a>. </dd>
<dt> <tt>-C <em>services_max</em></tt>, <tt>--services-max=<em>services_max</em></tt> </dt>
<dd> Maintain services for up to <em>services_max</em> service directories, including loggers.
This option is passed directly to <a href="s6-svscan.html">s6-svscan</a>. </dd>
<dt> <tt>-L <em>name_max</em></tt>, <tt>--name-max=<em>name_max</em></tt> </dt>
<dd> The maximum length of a name in the scan directory.
This option is passed directly to <a href="s6-svscan.html">s6-svscan</a>. </dd>
<dt> <tt>-t <em>rescan</em></tt>, <tt>--timeout=<em>rescan</em></tt> </dt>
<dd> Perform a scan every <em>rescan</em> milliseconds.
This option is passed directly to <a href="s6-svscan.html">s6-svscan</a>. </dd>
</dl>
<h2> Notes </h2>
<ul>
<li> <tt>s6-svscanboot</tt> is only useful in situations where it is
beneficial for a supervision tree to log its own output. In other situations,
it is better to launch <a href="s6-svscan.html">s6-svscan</a> directly. </li>
</ul>
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