man/sd_booted.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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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 &lt;systemd/sd-daemon.h&gt;</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/systemd/plain/src/sd-daemon.c"/>
  97                 resp. <ulink
  98                 url="http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-daemon.h"/></para>
  99
 100                 <para><function>sd_booted()</function> is implemented
 101                 in the reference implementation's
 102                 <filename>sd-daemon.c</filename> and
 103                 <filename>sd-daemon.h</filename> files. These
 104                 interfaces are available as shared library, which can
 105                 be compiled and linked to with the
 106                 <literal>libsystemd-daemon</literal>
 107                 <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 108                 file. Alternatively, applications consuming these APIs
 109                 may copy the implementation into their source
 110                 tree. For more details about the reference
 111                 implementation see
 112                 <citerefentry><refentrytitle>sd_daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
 113
 114                 <para>If the reference implementation is used as
 115                 drop-in files and -DDISABLE_SYSTEMD is set during
 116                 compilation this function will always return 0 and
 117                 otherwise become a NOP.</para>
 118         </refsect1>
 119
 120         <refsect1>
 121                 <title>See Also</title>
 122                 <para>
 123                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 124                         <citerefentry><refentrytitle>sd_daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 125                 </para>
 126         </refsect1>
 127
 128 </refentry>