man/systemd-notify.xml

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  10   Copyright 2010 Lennart Poettering
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  25
  26 <refentry id="systemd-notify"
  27     xmlns:xi="http://www.w3.org/2001/XInclude">
  28
  29   <refentryinfo>
  30     <title>systemd-notify</title>
  31     <productname>systemd</productname>
  32
  33     <authorgroup>
  34       <author>
  35         <contrib>Developer</contrib>
  36         <firstname>Lennart</firstname>
  37         <surname>Poettering</surname>
  38         <email>lennart@poettering.net</email>
  39       </author>
  40     </authorgroup>
  41   </refentryinfo>
  42
  43   <refmeta>
  44     <refentrytitle>systemd-notify</refentrytitle>
  45     <manvolnum>1</manvolnum>
  46   </refmeta>
  47
  48   <refnamediv>
  49     <refname>systemd-notify</refname>
  50     <refpurpose>Notify service manager about start-up completion and other daemon status changes</refpurpose>
  51   </refnamediv>
  52
  53   <refsynopsisdiv>
  54     <cmdsynopsis>
  55       <command>systemd-notify <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="opt" rep="repeat">VARIABLE=VALUE</arg></command>
  56     </cmdsynopsis>
  57   </refsynopsisdiv>
  58
  59   <refsect1>
  60     <title>Description</title>
  61
  62     <para><command>systemd-notify</command> may be called by daemon
  63     scripts to notify the init system about status changes. It can be
  64     used to send arbitrary information, encoded in an
  65     environment-block-like list of strings. Most importantly, it can be
  66     used for start-up completion notification.</para>
  67
  68     <para>This is mostly just a wrapper around
  69     <function>sd_notify()</function> and makes this functionality
  70     available to shell scripts. For details see
  71     <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  72     </para>
  73
  74     <para>The command line may carry a list of environment variables
  75     to send as part of the status update.</para>
  76
  77     <para>Note that systemd will refuse reception of status updates from this command unless
  78     <varname>NotifyAccess=</varname> is set for the service unit this command is called from.</para>
  79
  80     <para>Note that <function>sd_notify()</function> notifications may be attributed to units correctly only if either
  81     the sending process is still around at the time PID 1 processes the message, or if the sending process is
  82     explicitly runtime-tracked by the service manager. The latter is the case if the service manager originally forked
  83     off the process, i.e. on all processes that match <varname>NotifyAccess=</varname><option>main</option> or
  84     <varname>NotifyAccess=</varname><option>exec</option>. Conversely, if an auxiliary process of the unit sends an
  85     <function>sd_notify()</function> message and immediately exits, the service manager might not be able to properly
  86     attribute the message to the unit, and thus will ignore it, even if
  87     <varname>NotifyAccess=</varname><option>all</option> is set for it.</para>
  88
  89     <para><command>systemd-notify</command> will first attempt to invoke <function>sd_notify()</function> pretending to
  90     have the PID of the invoking process. This will only succeed when invoked with sufficient privileges. On failure,
  91     it will then fall back to invoking it under its own PID. This behaviour is useful in order that when the tool is
  92     invoked from a shell script the shell process — and not the <command>systemd-notify</command> process — appears as
  93     sender of the message, which in turn is helpful if the shell process is the main process of a service, due to the
  94     limitations of <varname>NotifyAccess=</varname><option>all</option> described above.</para>
  95   </refsect1>
  96
  97   <refsect1>
  98     <title>Options</title>
  99
 100     <para>The following options are understood:</para>
 101
 102     <variablelist>
 103       <varlistentry>
 104         <term><option>--ready</option></term>
 105
 106         <listitem><para>Inform the init system about service start-up
 107         completion. This is equivalent to <command>systemd-notify
 108         READY=1</command>. For details about the semantics of this
 109         option see
 110         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
 111       </varlistentry>
 112
 113       <varlistentry>
 114         <term><option>--pid=</option></term>
 115
 116         <listitem><para>Inform the init system about the main PID of
 117         the daemon. Takes a PID as argument. If the argument is
 118         omitted, the PID of the process that invoked
 119         <command>systemd-notify</command> is used. This is equivalent
 120         to <command>systemd-notify MAINPID=$PID</command>. For details
 121         about the semantics of this option see
 122         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
 123       </varlistentry>
 124
 125       <varlistentry>
 126         <term><option>--status=</option></term>
 127
 128         <listitem><para>Send a free-form status string for the daemon
 129         to the init systemd. This option takes the status string as
 130         argument. This is equivalent to <command>systemd-notify
 131         STATUS=…</command>. For details about the semantics of this
 132         option see
 133         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
 134       </varlistentry>
 135
 136       <varlistentry>
 137         <term><option>--booted</option></term>
 138
 139         <listitem><para>Returns 0 if the system was booted up with
 140         systemd, non-zero otherwise. If this option is passed, no
 141         message is sent. This option is hence unrelated to the other
 142         options. For details about the semantics of this option, see
 143         <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>. An
 144         alternate way to check for this state is to call
 145         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 146         with the <command>is-system-running</command> command. It will
 147         return <literal>offline</literal> if the system was not booted
 148         with systemd.  </para></listitem>
 149       </varlistentry>
 150
 151       <xi:include href="standard-options.xml" xpointer="help" />
 152       <xi:include href="standard-options.xml" xpointer="version" />
 153     </variablelist>
 154
 155   </refsect1>
 156
 157   <refsect1>
 158     <title>Exit status</title>
 159
 160     <para>On success, 0 is returned, a non-zero failure code
 161     otherwise.</para>
 162   </refsect1>
 163
 164   <refsect1>
 165     <title>Example</title>
 166
 167     <example>
 168       <title>Start-up Notification and Status Updates</title>
 169
 170       <para>A simple shell daemon that sends start-up notifications
 171       after having set up its communication channel. During runtime it
 172       sends further status updates to the init system:</para>
 173
 174       <programlisting>#!/bin/bash
 175
 176 mkfifo /tmp/waldo
 177 systemd-notify --ready --status="Waiting for data…"
 178
 179 while : ; do
 180         read a &lt; /tmp/waldo
 181         systemd-notify --status="Processing $a"
 182
 183         # Do something with $a …
 184
 185         systemd-notify --status="Waiting for data…"
 186 done</programlisting>
 187     </example>
 188   </refsect1>
 189
 190   <refsect1>
 191     <title>See Also</title>
 192     <para>
 193       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 194       <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 195       <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 196       <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 197       <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 198     </para>
 199   </refsect1>
 200
 201 </refentry>