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<title>s6: the s6-instance-create program</title>
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<p>
<a href="index.html">s6</a><br />
<a href="//skarnet.org/software/">Software</a><br />
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<h1> The s6-instance-create program </h1>
<p>
s6-instance-create creates a new instance of a currently supervised
<a href="instances.html">instanced service</a>.
</p>
<h2> Interface </h2>
<pre>
s6-instance-create [ -d | -D ] [ -P ] [ -f ] [ -t <em>timeout</em> ] <em>servicedir</em> <em>name</em>
</pre>
<ul>
<li> s6-instance-create expects a running, supervised
<a href="instances.html">instanced service</a> in <em>servicedir</em>.
This service typically has been created by linking the result of an
<a href="s6-instance-maker.html">s6-instance-maker</a> invocation into
an existing <a href="scandir.html">scan directory</a>. </li>
<li> s6-instance-create creates a new instance of that service, named
<em>name</em>. Depending on the given options, it may start it
immediately, or keep it down until a later
<a href="s6-instance-control.html">s6-instance-control</a> invocation. </li>
<li> It waits for the new instance to be ready to take commands from
<a href="s6-instance-control.html">s6-instance-control</a>. </li>
<li> It exits 0. </li>
</ul>
<h2> Exit codes </h2>
<ul>
<li> 0: success </li>
<li> 99: timeout while waiting for the instance supervisor to start </li>
<li> 100: wrong usage </li>
<li> 111: system call failed </li>
</ul>
<h2> Options </h2>
<ul>
<li> <tt>-d</tt> : down. The instance supervisor will be started, but the instance
itself will remain down. Any <tt>down</tt> file for the instance will be
deleted. By default, if neither the <tt>-d</tt> nor <tt>-D</tt> options have
been given, the supervisor auto-starts the instance as soon as it runs. </li>
<li> <tt>-D</tt> : down, and stay down. The instance supervisor will be started,
but the instance itself will remain down. A <tt>down</tt> file
will be created for the instance. By default, if neither the <tt>-d</tt> nor <tt>-D</tt> options have
been given, the supervisor auto-starts the instancece as soon as it runs. </li>
<li> <tt>-P</tt> : public. Everyone will be able to subscribe to the
instance supervisor's notification. By default, only processes running with the same gid
as the instanced service can subscribe to it. </li>
<li> <tt>-f</tt> : force permissions. You should never need to use this
option, it is only there for testing purposes. </li>
<li> <tt>-t <em>timeout</em></tt> : if the instance supervisor has not started
after <em>timeout</em> milliseconds, s6-instance-create will print a message
to stderr and exit 99. By default, <em>timeout</em> is 0, which means no time
limit. </li>
</ul>
<h2> Notes </h2>
<ul>
<li> s6-instance-create is similar to
<a href="s6-svlink.html">s6-svlink</a>, because it uses the same underlying
library functions. Under the hood, an instance is a regular service running
on a supervision tree that is specific to the instanced service, and
s6-instance-create adds a service directory to that tree and ensures it gets
supervised. </li>
<li> If the template for the service is logged, then s6-instance-create will
wait until supervisors have been spawned for both the instance and its logger. </li>
<li> s6-instance-create and <a href="s6-instance-delete.html">s6-instance-delete</a>
are relatively expensive operations, because they have to recursively copy or
delete directories and use the <a href="libs6/ftrigr.html">synchronization mechanism</a>
with the instance supervisor, compared to
<a href="s6-instance-control.html">s6-instance-control</a> which only has to send
commands to already existing supervisors. If you are going to turn instances on and
off on a regular basis, it is more efficient to keep the instance existing and control
it with <a href="s6-instance-control.html">s6-instance-control</a> than it is to
repeatedly create and delete it. </li>
</ul>
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