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<title>s6: the s6-fdholder-getdump 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 <tt>s6-fdholder-getdump</tt> program </h1>
<p>
<tt>s6-fdholder-getdump</tt> connects to a
<a href="s6-fdholderd.html">fd-holding daemon</a> listening on a
Unix domain socket, and retrieves its entire state: file descriptors with
their identifiers and expiration dates. It then executes a program with
those file descriptors still open, and the state stored in the
environment.
</p>
<h2> Interface </h2>
<pre>
s6-fdholder-getdump [ -t <em>timeout</em> ] <em>path</em> <em>prog...</em>
</pre>
<ul>
<li> s6-fdholder-getdump executes into <tt><a href="s6-ipcclient.html">s6-ipcclient</a> <em>path</em>
<a href="s6-fdholder-getdumpc.html">s6-fdholder-getdumpc</a> <em>prog...</em></tt>.
It does nothing else: it is just a convenience program.
The <a href="s6-ipcclient.html">s6-ipcclient</a> program connects
to a Unix socket at <em>path</em>, and the
<a href="s6-fdholder-getdumpc.html">s6-fdholder-getdumpc</a> program
gets the server's state over the socket. </li>
<li> It executes into <em>prog...</em> with as many more open
file descriptors as there were in the daemon, and information about those
file descriptors in the environment. </li>
</ul>
<h2> Options </h2>
<ul>
<li> <tt>-t <em>timeout</em></tt> : if the operation cannot be
processed in <em>timeout</em> milliseconds, then fail with an error message.
Communications with the server should be near-instant, so this option is
only here to protect users against programming errors (connecting to the
wrong socket, for instance). </li>
</ul>
<h2> Usage example </h2>
<pre>
s6-fdholder-getdump /service/fdholderd/s s6-fdholder-setdump /service/fdholderd-2/s
</pre>
<p>
will get the state of the s6-fdholderd daemon listening on the <tt>/service/fdholderd/s</tt>
socket, and transmit it to the other s6-fdholderd daemon listening on the
<tt>/service/fdholderd-2/s</tt> socket. Note that in this precise case,
the <a href="s6-fdholder-transferdump.html">s6-fdholder-transferdump</a>
program does the same thing more efficiently.
</p>
<h2> Notes </h2>
<ul>
<li> s6-fdholder-getdump really executes into <tt>s6-ipcclient
s6-fdholder-getdumpc
<a href="//skarnet.org/software/execline/fdclose.html">fdclose</a>
6 fdclose 7 <em>prog...</em></tt>, so that <em>prog...</em> does not
have a connection with the fd-holding daemon anymore. If you want to
keep the server connection open for <em>prog...</em>, use
<tt>s6-ipcclient s6-fdholder-getdumpc</tt> manually. </li>
<li> The exact format of the environment given to <em>prog...</em>
is described in the
<a href="s6-fdholder-getdumpc.html">s6-fdholder-getdumpc</a> page. </li>
<li> Getting the whole state of a s6-fdholderd daemon requires specific
privileges. Make sure you properly
<a href="s6-fdholderd.html#configuration">configure the s6-fdholderd
access rights</a> so your client can perform that operation. </li>
</ul>
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