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fsck: skip checking / if it is writable
[elogind.git] / man / sd_booted.xml
1 <?xml version='1.0'?> <!--*-nxml-*-->
2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
4
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8   Copyright 2010 Lennart Poettering
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23
24 <refentry id="sd_booted">
25
26         <refentryinfo>
27                 <title>sd_booted</title>
28                 <productname>systemd</productname>
29
30                 <authorgroup>
31                         <author>
32                                 <contrib>Developer</contrib>
33                                 <firstname>Lennart</firstname>
34                                 <surname>Poettering</surname>
35                                 <email>lennart@poettering.net</email>
36                         </author>
37                 </authorgroup>
38         </refentryinfo>
39
40         <refmeta>
41                 <refentrytitle>sd_booted</refentrytitle>
42                 <manvolnum>3</manvolnum>
43         </refmeta>
44
45         <refnamediv>
46                 <refname>sd_booted</refname>
47                 <refpurpose>Test whether the system is running the systemd init system.</refpurpose>
48         </refnamediv>
49
50         <refsynopsisdiv>
51                 <funcsynopsis>
52                         <funcsynopsisinfo>#include "sd-daemon.h"</funcsynopsisinfo>
53
54                         <funcprototype>
55                                 <funcdef>int <function>sd_booted</function></funcdef>
56                                 <paramdef>void</paramdef>
57                         </funcprototype>
58                 </funcsynopsis>
59         </refsynopsisdiv>
60
61         <refsect1>
62                 <title>Description</title>
63                 <para><function>sd_booted()</function> checks whether
64                 the system was booted up using the systemd init system.</para>
65         </refsect1>
66
67         <refsect1>
68                 <title>Return Value</title>
69
70                 <para>On failure, this call returns a negative
71                 errno-style error code. If the system was booted up
72                 with systemd as init system, this call returns a
73                 positive return value, zero otherwise.</para>
74         </refsect1>
75
76         <refsect1>
77                 <title>Notes</title>
78
79                 <para>This function is provided by the reference
80                 implementation of APIs for new-style daemons and
81                 distributed with the systemd package. The algorithm it
82                 implements is simple, and can easily be reimplemented
83                 in daemons if it is important to support this
84                 interface without using the reference
85                 implementation.</para>
86
87                 <para>Internally, this function checks whether the
88                 <filename>/sys/fs/cgroup/systemd</filename> virtual file
89                 system is mounted, by comparing the st_dev value of
90                 the <function>stat()</function> data of
91                 <filename>/sys/fs/cgroup</filename> and
92                 <filename>/sys/fs/cgroup/systemd</filename>.</para>
93
94                 <para>For details about the algorithm check the
95                 liberally licensed reference implementation sources:
96                 <ulink url="http://cgit.freedesktop.org/systemd/tree/src/sd-daemon.c"/>
97                 resp. <ulink
98                 url="http://cgit.freedesktop.org/systemd/tree/src/sd-daemon.h"/></para>
99
100                 <para><function>sd_booted()</function> is implemented
101                 in the reference implementation's drop-in
102                 <filename>sd-daemon.c</filename> and
103                 <filename>sd-daemon.h</filename> files. It is
104                 recommended that applications consuming these APIs
105                 copy the implementation into their source tree. For
106                 more details about the reference implementation see
107                 <citerefentry><refentrytitle>sd_daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry></para>
108
109                 <para>If -DDISABLE_SYSTEMD is set during compilation
110                 this function will always return 0 and otherwise
111                 become a NOP.</para>
112         </refsect1>
113
114         <refsect1>
115                 <title>See Also</title>
116                 <para>
117                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
118                         <citerefentry><refentrytitle>sd_daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>
119                 </para>
120         </refsect1>
121
122 </refentry>