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<title>nsss: the nsssd-unix program</title>
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<p>
<a href="index.html">nsss</a><br />
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</p>
<h1> The nsssd-unix program </h1>
<p>
nsssd-unix is a daemon providing a backend for clients using the
<a href="libnsss/">nsss library</a> - more precisely, clients using
the <a href="libnsss/nsss-all.html">nsss-all</a> or
the <a href="libnsss/nsss-switch.html">nsss-switch</a> functions.
</p>
<p>
The nsssd-unix backend is a simple one. It simply fetches user/group/shadow
information from the <tt>/etc/passwd</tt>, <tt>/etc/group</tt> and
<tt>/etc/shadow</tt> files. The same information can be directly obtained
by a client if it uses the <a href="libnsss/nsss-unix.html">nsss-unix</a>
functions, without the overhead of going through an independent process.
However, setting up a nsssd-unix service can still be useful:
</p>
<ul>
<li> For testing purposes </li>
<li> As a placeholder service that will be replaced later with a more
complex backend </li>
<li> ... </li>
</ul>
<p>
nsssd-unix is not meant to be called directly; instead, it is expected to be run from
a script as a part of a "nsssd"
<a href="//skarnet.org/software/s6/localservice.html">local service</a>.
</p>
<p>
The <tt>examples/</tt> subdirectory of the nsss package provides examples
on how to run such a service.
The simplest way to do so, for testing purposes, is a command line such as:
</p>
<pre>s6-ipcserver -l0 /run/service/nsss/s nsssd-unix</pre>
<p>
<tt>/run/service/nsss/s</tt> is the default place where nsss's
implementation of the <tt>pwd.h</tt>, <tt>grp.h</tt> and <tt>shadow.h</tt>
functions expects the nsssd
service to be. It can be changed at nsss build time by giving the
<tt>--with-nsssd-socket=PATH</tt> option to configure.
</p>
<p>
nsssd-unix does not listen to the socket itself: it reads from its
standard input and writes to its standard output. It relies
on a superserver such as
<a href="//skarnet.org/software/s6/s6-ipcserver.html">s6-ipcserver</a>
to manage connections to the socket. An instance of nsssd-unix is run
for every client connection.
</p>
<p>
If fine-grained authorizations are required (only allowing
certain users and groups to connect to the service), the superserver
can be configured to enforce them.
</p>
<p>
nsssd-unix does not need to run as root, provided it can read the files
database.
It is recommended to create a <em>nsss</em> user and group, dedicated to
the nsssd service, and run the superserver as this user and group.
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