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<title>s6: the s6-svperms 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/">skarnet.org</a>
</p>
<h1> The <tt>s6-svperms</tt> program </h1>
<p>
<tt>s6-svperms</tt> allows the user to see, or modify, for a given
list of services: who can read their states, who can send them
control commands, and who can subscribe to up/down events for those
services.
</p>
<h2> Interface </h2>
<pre>
s6-svperms [ -v ] [ -u | -g <em>group</em> | -G <em>group</em> | -o | -O <em>group</em> ] [ -e | -E <em>group</em> ] <em>servicedirs...</em>
</pre>
<p>
Without options, or with only the <tt>-v</tt> option,
<tt>s6-svperms</tt> prints 3 lines to stdout for every service directory
listed in <em>servicedirs</em>. Every line contains the name
of the service directory, then the following information:
</p>
<ul>
<li> <tt>status:</tt> - indicates who is allowed to read status
information on the service, with commands such as
<a href="s6-svstat.html">s6-svstat</a> or
<a href="s6-svdt.html">s6-svdt</a>. The values can be <tt>owner</tt>,
for only the owner of the service; <tt>group: <em>name</em></tt>, for
the owner and members of group <em>name</em>; or <tt>public</tt>,
for all users. </li>
<li> <tt>control:</tt> - indicates who is allowed to send control
commands to the service, with commands such as
<a href="s6-svc.html">s6-svc</a>. The values can be <tt>owner</tt>,
for only the owner of the service; or <tt>group: <em>name</em></tt>,
for the owner and members of group <em>name</em>. </li>
<li> <tt>events:</tt> - indicates who is allowed to subscribed to
events sent by <a href="s6-supervise.html">s6-supervise</a> for this
service, with commands such as <a href="s6-svwait.html">s6-svwait</a>
or <a href="s6-svlisten1.html">s6-svlisten1</a>. The values can be
<tt>group: <em>name</em></tt>, for the owner and members of group
<em>name</em>, or <tt>public</tt>, for all users.
</ul>
<p>
If something goes wrong while reading a part of the configuration of
a service directory, <tt>s6-svperms</tt> does not print the corresponding
line to stdout; instead, it prints a warning message to stderr.
</p>
<p>
When invoked with other options, <tt>s6-svperms</tt> modifies the
permissions of the service directories listed in <em>servicedirs...</em> as
specified by the options. The same permissions will be applied to all
the services listed in <em>servicedirs...</em>.
</p>
<h2> Options </h2>
<ul>
<li> <tt>-v</tt> : re-read the permissions after writing them, and
print them to stdout.
<li> <tt>-u</tt> : restrict the <tt>status:</tt> and <tt>control:</tt>
permissions to <tt>owner</tt>: only the owner of a service directory will
be able to read its state or control the service. This is the default when
<a href="s6-supervise.html">s6-supervise</a> starts a service for the first
time. </li>
<li> <tt>-g <em>group</em></tt> : allow members of group
<em>group</em> to read the status of the service, but not to control it -
control will be restricted to the owner. </li>
<li> <tt>-G <em>group</em></tt> : allow members of group
<em>group</em> to read <em>and</em> control the service. </li>
<li> <tt>-o</tt> : allow everyone to read the status of the service,
but restrict <tt>control:</tt> to the owner. </li>
<li> <tt>-O <em>group</em></tt> : allow everyone to read the
status, and allow members of group <em>group</em> to control the
service. </li>
<li> <tt>-e</tt> : allow everyone to subscribe to events. </li>
<li> <tt>-E <em>group</em></tt> : only allow members of group
<em>group</em> to subscribe to events. This is the default when
<a href="s6-supervise.html">s6-supervise</a> starts a service for the first
time, with <em>group</em> being the primary group of the s6-supervise
process (most likely <tt>root</tt>). </li>
</ul>
<p>
<em>group</em> is normally a group name that will be searched in the group
database. But if it starts with a colon (<tt>:</tt>), the rest of <em>group</em>
will be interpreted as a numerical gid, and the group database will not be read.
</p>
<h2> Exit codes </h2>
<ul>
<li> 0: success </li>
<li> 1: something went wrong when reading permissions in one of the service directories </li>
<li> 100: wrong usage </li>
<li> 111: system call failed </li>
</ul>
<h2> Notes </h2>
<ul>
<li> The default (restrictive) permissions are safe. </li>
<li> Unless operation of a service is restricted information, it is also
safe to make <tt>status:</tt> more permissive. </li>
<li> Opening <tt>control:</tt> to a group can be useful for instance in a
shared administration situation when individual administrators are not given
full root powers. </li>
<li> Making <tt>events:</tt> public bears a small risk of a local DoS attack
preventing more subscriptions to events, so it is not recommended for
supervision trees where such subscriptions are critical to operations - such
as a set of root services managed by
<a href="//skarnet.org/software/s6-rc/">s6-rc</a>. </li>
</ul>
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