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<title>s6: the s6-envuidgid program</title>
<meta name="Description" content="s6: the s6-envuidgid program" />
<meta name="Keywords" content="s6 command s6-envuidgid uid gid environment modification" />
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<p>
<a href="index.html">s6</a><br />
<a href="http://skarnet.org/software/">Software</a><br />
<a href="http://skarnet.org/">skarnet.org</a>
</p>
<h1> The s6-envuidgid program </h1>
<p>
s6-envuidgid sets the UID, GID and GIDLIST environment variables,
then executes into another program.
</p>
<h2> Interface </h2>
<pre>
s6-envuidgid <em>account</em> <em>prog...</em>
</pre>
<ul>
<li> s6-envuidgid looks <em>account</em> up by name in the account database. </li>
<li> If <em>account</em> is unknown, it exits 1. </li>
<li> It sets the UID environment variable to <em>account</em>'s uid, and the GID
environment variable to <em>account</em>'s gid. </li>
<li> It also sets the GIDLIST environment variable to a comma-separated list of
supplementary group ids <em>account</em> is a member of according to the
group database. (If <em>account</em> doesn't belong to any other group than its
primary group, GIDLIST is still set, but empty.) </li>
<li> Then it executes into <em>prog...</em>. </li>
</ul>
<h2> Notes </h2>
<p>
s6-envuidgid behaves like
<a href="http://cr.yp.to/daemontools/envuidgid.html">envuidgid</a>, except that:
</p>
<ul>
<li> it also handles supplementary groups </li>
<li> It exits 1 if <em>account</em> does not exist. </li>
</ul>
<p>
s6-envuidgid is useful when running a program that must start as root but can
drop its privileges later. Such a program can read its new uid/gid/groups info
from the UID, GID and GIDLIST environment variables. Superservers such as
<a href="http://skarnet.org/software/s6-networking/s6-tcpserver4.html">s6-tcpserver4</a>
make use of this.
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