summaryrefslogtreecommitdiff
path: root/doc/s6-fdholder-getdump.html
blob: a339b71c6b04b7eec23f9bb68ab6b51601b39ec5 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <meta http-equiv="Content-Language" content="en" />
    <title>s6: the s6-fdholder-getdump program</title>
    <meta name="Description" content="s6: the s6-fdholder-getdump program" />
    <meta name="Keywords" content="s6 s6-fdholder fd-holding fd-holder fd dump retrieval unix socket activation" />
    <!-- <link rel="stylesheet" type="text/css" href="http://skarnet.org/default.css" /> -->
  </head>
<body>

<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 <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&nbsp;<em>timeout</em></tt>&nbsp;: 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="http://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>

</body>
</html>