sd_booted.xml 5.39 KB
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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
        "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<!--
  This file is part of systemd.

  Copyright 2010 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
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  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
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  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
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  Lesser General Public License for more details.
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  You should have received a copy of the GNU Lesser General Public License
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  along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->

<refentry id="sd_booted">

        <refentryinfo>
                <title>sd_booted</title>
                <productname>systemd</productname>

                <authorgroup>
                        <author>
                                <contrib>Developer</contrib>
                                <firstname>Lennart</firstname>
                                <surname>Poettering</surname>
                                <email>lennart@poettering.net</email>
                        </author>
                </authorgroup>
        </refentryinfo>

        <refmeta>
                <refentrytitle>sd_booted</refentrytitle>
                <manvolnum>3</manvolnum>
        </refmeta>

        <refnamediv>
                <refname>sd_booted</refname>
                <refpurpose>Test whether the system is running the systemd init system.</refpurpose>
        </refnamediv>

        <refsynopsisdiv>
                <funcsynopsis>
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                        <funcsynopsisinfo>#include &lt;systemd/sd-daemon.h&gt;</funcsynopsisinfo>
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                        <funcprototype>
                                <funcdef>int <function>sd_booted</function></funcdef>
                                <paramdef>void</paramdef>
                        </funcprototype>
                </funcsynopsis>
        </refsynopsisdiv>

        <refsect1>
                <title>Description</title>
                <para><function>sd_booted()</function> checks whether
                the system was booted up using the systemd init system.</para>
        </refsect1>

        <refsect1>
                <title>Return Value</title>

                <para>On failure, this call returns a negative
                errno-style error code. If the system was booted up
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                with systemd as init system, this call returns a
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                positive return value, zero otherwise.</para>
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        </refsect1>

        <refsect1>
                <title>Notes</title>

                <para>This function is provided by the reference
                implementation of APIs for new-style daemons and
                distributed with the systemd package. The algorithm it
                implements is simple, and can easily be reimplemented
                in daemons if it is important to support this
                interface without using the reference
                implementation.</para>

                <para>Internally, this function checks whether the
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                <filename>/sys/fs/cgroup/systemd</filename> virtual file
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                system is mounted, by comparing the st_dev value of
                the <function>stat()</function> data of
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                <filename>/sys/fs/cgroup</filename> and
                <filename>/sys/fs/cgroup/systemd</filename>.</para>
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                <para>For details about the algorithm check the
                liberally licensed reference implementation sources:
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                <ulink url="http://cgit.freedesktop.org/systemd/systemd/plain/src/sd-daemon.c"/>
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                resp. <ulink
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                url="http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-daemon.h"/></para>
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                <para><function>sd_booted()</function> is implemented
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                in the reference implementation's
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                <filename>sd-daemon.c</filename> and
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                <filename>sd-daemon.h</filename> files. These
                interfaces are available as shared library, which can
                be compiled and linked to with the
                <literal>libsystemd-daemon</literal>
                <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
                file. Alternatively, applications consuming these APIs
                may copy the implementation into their source
                tree. For more details about the reference
                implementation see
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                <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
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                <para>If the reference implementation is used as
                drop-in files and -DDISABLE_SYSTEMD is set during
                compilation this function will always return 0 and
                otherwise become a NOP.</para>
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        </refsect1>

        <refsect1>
                <title>See Also</title>
                <para>
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                        <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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                        <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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                </para>
        </refsect1>

</refentry>