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<title>s6: the s6-svunlink program</title>
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<h1> The s6-svunlink program </h1>
<p>
<tt>s6-svunlink</tt> unlinks a <a href="servicedir.html">service
directory</a> from a <a href="scandir.html">scan directory</a>, then
notifies <a href="s6-svscan.html">s6-svscan</a> that a service has
been unregistered. It waits until the <a href="s6-supervise.html">s6-supervise</a>
supervisor process managing the service has disappeared, then exits.
</p>
<p>
The point of <tt>s6-svunlink</tt> is to help integrate
service directories into an existing service manager sequence and
eliminate race conditions.
</p>
<h2> Interface </h2>
<pre>
s6-svunlink [ -X ] [ -t <em>timeout</em> ] <em>scandir</em> <em>name</em>
</pre>
<ul>
<li> <tt>s6-svunlink</tt> expects a running <a href="s6-svscan.html">s6-svscan</a>
process on <em>scandir</em> and a fully functional supervised service on
<a href="servicedir.html">service directory</a> in <em>scandir</em><tt>/</tt><em>name</em>,
which must be a symbolic link to a real directory located somewhere else. </li>
<li> It deletes the <em>scandir</em><tt>/</tt><em>name</em> symlink. </li>
<li> It sends a command to <a href="s6-svscan.html">s6-svscan</a> to signal it
that a service has disappeared. </li>
<li> It waits for the <a href="s6-supervise.html">s6-supervise</a> process
managing the service directory to exit. </li>
<li> It exits 0. </li>
</ul>
<h2> Exit codes </h2>
<ul>
<li> 0: success </li>
<li> 100: wrong usage </li>
<li> 111: system call failed </li>
</ul>
<h2> Options </h2>
<ul>
<li> <tt>-X</tt> : don't wait. <tt>s6-svunlink</tt> will exit right
away, without waiting for the supervisor to exit first. </li>
<li> <tt>-t <em>timeout</em></tt> : if the supervisor has not exited
after <em>timeout</em> milliseconds, <tt>s6-svunlink</tt> will still exit.
The default is 0, meaning no time limit. </li>
</ul>
<h2> Notes </h2>
<ul>
<li> Using <tt>s6-svunlink</tt> to stop services is a suboptimal pattern:
starting and stopping supervisors is a heavier operation than just stopping
services. The simpler, more efficient pattern is to simply perform
<a href="s6-svc.html">s6-svc -dwD <em>scandir</em><tt>/</tt><em>name</em></a>,
which only commands, and waits for, the death of the service, without
impacting the supervisor. Nevertheless, for symmetry with
<a href="s6-svlink.html">s6-svlink</a>, this program is provided. </li>
<li> <tt>s6-svunlink</tt> is a destructor; as is, it returns 0 even in
situations that are nominal failures. For instance, it returns 0 even
if its timeout expires; the rationale is that there is no sensible action
for the user to do if this error is reported. <tt>s6-svunlink</tt> only
reports errors when they uncover a deeper problem in the system. </li>
<li> <tt>s6-svunlink</tt> sends an <a href="s6-svscanctl.html">s6-svscanctl -an</a>
command to <em>scandir</em>, which means that the system's view of services
will be refreshed and inactive services will be killed and unsupervised.
Depending on what links exist in <em>scandir</em>, new
services may appear, and other services than <em>name</em> may disappear. </li>
</ul>
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