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<title>s6: the s6-svscanctl program</title>
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<a href="index.html">s6</a><br />
<a href="//skarnet.org/software/">Software</a><br />
<a href="//skarnet.org/">skarnet.org</a>
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<h1> The s6-svscanctl program </h1>
<p>
s6-svscanctl sends commands to a running <a href="s6-svscan.html">s6-svscan</a>
process.
</p>
<h2> Interface </h2>
<pre>
s6-svscanctl [ -phratszbnNiq0678 ] <em>svscandir</em>
</pre>
<p>
s6-svscanctl sends the given series of commands to the
<a href="s6-svscan.html">s6-svscan</a> process monitoring the
<em>svscandir</em> directory, then exits 0. It exits 111 if it cannot send
a command, or 100 if no s6-svscan process is running on <em>svscandir</em>.
</p>
<h2> Options </h2>
<ul>
<li> <tt>-p</tt> : poweroff mode. s6-svscan will exec into
<tt>./.s6-svscan/finish poweroff</tt> when it is told to terminate. </li>
<li> <tt>-h</tt> : Hangup. s6-svscan will send a SIGHUP to all the
maintained s6-supervise processes, then run its finish procedure. </li>
<li> <tt>-r</tt> : reboot mode. s6-svscan will exec into
<tt>./.s6-svscan/finish reboot</tt> when it is told to terminate. This
is s6-svscan's default mode.</li>
<li> <tt>-a</tt> : Alarm. s6-svscan will immediately perform a scan
of <em>svscandir</em> to check for services. </li>
<li> <tt>-t</tt> : Terminate. s6-svscan will send a
SIGTERM to all the s6-supervise processes supervising a service and a
SIGHUP to all the s6-supervise processes supervising a logger, then run its
finish procedure. </li>
<li> <tt>-s</tt> : halt mode. s6-svscan will exec into
<tt>./.s6-svscan/finish halt</tt> when it is told to terminate. </li>
<li> <tt>-z</tt> : destroy zombies. Immediately triggers s6-svscan's
reaper mechanism. </li>
<li> <tt>-b</tt> : abort. s6-svscan will exec into its finishing
procedure. It will not kill any of the maintained s6-supervise processes. </li>
<li> <tt>-n</tt> : nuke. s6-svscan will kill all the
s6-supervise processes it has launched but that did not match a service
directory last time <em>svscandir</em> was scanned, i.e. it prunes the
supervision tree so that it matches exactly what was in <em>svscandir</em>
at the time of the last scan. A SIGTERM is sent to the s6-supervise processes
supervising services and a SIGHUP is sent to the s6-supervise processes
supervising loggers. </li>
<li> <tt>-N</tt> : Really nuke. Does the same thing as <tt>-n</tt>,
except that SIGTERM is sent to all the relevant s6-supervise processes, even
if they are supervising loggers. That means that the logger processes will
be killed with a SIGTERM instead of being allowed to exit at their own pace. </li>
<li> <tt>-i</tt> : Interrupt. Equivalent to <tt>-rt</tt> : s6-svscan
will terminate in reboot mode. </li>
<li> <tt>-q</tt> : Quit. s6-svscan will send all its s6-supervise processes
a SIGTERM, then exec into its finish procedure. </li>
<li> <tt>-0</tt> : Halt. Equivalent to <tt>-st</tt> : s6-svscan will
terminate in halt mode. </li>
<li> <tt>-6</tt> : Reboot. Equivalent to <tt>-i</tt>. </li>
<li> <tt>-7</tt> : Poweroff. Equivalent to <tt>-pt</tt>: s6-svscan will
terminate in poweroff mode. </li>
<li> <tt>-8</tt> : Other. s6-svscan will terminate in "other" mode. </li>
</ul>
<h2> Usage examples </h2>
<pre> s6-svscanctl -an /service </pre>
<p>
Updates the process supervision tree
to exactly match the services listed in <tt>/service</tt>.
</p>
<pre> s6-svscanctl -6 /service </pre>
<p>
Orders the s6-svscan process monitoring <tt>/service</tt> to exit in
reboot mode: all the supervision tree at <tt>/service</tt> will be terminated,
and s6-svscan will execute into the <tt>/service/.s6-svscan/finish</tt>
script with the <tt>reboot</tt> argument.
</p>
<h2> Internals </h2>
<p>
s6-svscanctl writes control commands into the <tt><em>svscandir</em>/.s6-svscan/control</tt>
FIFO. A s6-svscan process running on <em>svscandir</em> will be listening to this FIFO,
and will read and interpret those commands.
</p>
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