man/systemd-notify.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   This file is part of systemd.
   9
  10   Copyright 2010 Lennart Poettering
  11 -->
  12
  13 <refentry id="systemd-notify"
  14     xmlns:xi="http://www.w3.org/2001/XInclude">
  15
  16   <refentryinfo>
  17     <title>systemd-notify</title>
  18     <productname>systemd</productname>
  19
  20     <authorgroup>
  21       <author>
  22         <contrib>Developer</contrib>
  23         <firstname>Lennart</firstname>
  24         <surname>Poettering</surname>
  25         <email>lennart@poettering.net</email>
  26       </author>
  27     </authorgroup>
  28   </refentryinfo>
  29
  30   <refmeta>
  31     <refentrytitle>systemd-notify</refentrytitle>
  32     <manvolnum>1</manvolnum>
  33   </refmeta>
  34
  35   <refnamediv>
  36     <refname>systemd-notify</refname>
  37     <refpurpose>Notify service manager about start-up completion and other daemon status changes</refpurpose>
  38   </refnamediv>
  39
  40   <refsynopsisdiv>
  41     <cmdsynopsis>
  42       <command>systemd-notify <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="opt" rep="repeat">VARIABLE=VALUE</arg></command>
  43     </cmdsynopsis>
  44   </refsynopsisdiv>
  45
  46   <refsect1>
  47     <title>Description</title>
  48
  49     <para><command>systemd-notify</command> may be called by daemon
  50     scripts to notify the init system about status changes. It can be
  51     used to send arbitrary information, encoded in an
  52     environment-block-like list of strings. Most importantly, it can be
  53     used for start-up completion notification.</para>
  54
  55     <para>This is mostly just a wrapper around
  56     <function>sd_notify()</function> and makes this functionality
  57     available to shell scripts. For details see
  58     <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  59     </para>
  60
  61     <para>The command line may carry a list of environment variables
  62     to send as part of the status update.</para>
  63
  64     <para>Note that systemd will refuse reception of status updates from this command unless
  65     <varname>NotifyAccess=</varname> is set for the service unit this command is called from.</para>
  66
  67     <para>Note that <function>sd_notify()</function> notifications may be attributed to units correctly only if either
  68     the sending process is still around at the time PID 1 processes the message, or if the sending process is
  69     explicitly runtime-tracked by the service manager. The latter is the case if the service manager originally forked
  70     off the process, i.e. on all processes that match <varname>NotifyAccess=</varname><option>main</option> or
  71     <varname>NotifyAccess=</varname><option>exec</option>. Conversely, if an auxiliary process of the unit sends an
  72     <function>sd_notify()</function> message and immediately exits, the service manager might not be able to properly
  73     attribute the message to the unit, and thus will ignore it, even if
  74     <varname>NotifyAccess=</varname><option>all</option> is set for it.</para>
  75
  76     <para><command>systemd-notify</command> will first attempt to invoke <function>sd_notify()</function> pretending to
  77     have the PID of the invoking process. This will only succeed when invoked with sufficient privileges. On failure,
  78     it will then fall back to invoking it under its own PID. This behaviour is useful in order that when the tool is
  79     invoked from a shell script the shell process — and not the <command>systemd-notify</command> process — appears as
  80     sender of the message, which in turn is helpful if the shell process is the main process of a service, due to the
  81     limitations of <varname>NotifyAccess=</varname><option>all</option> described above.</para>
  82   </refsect1>
  83
  84   <refsect1>
  85     <title>Options</title>
  86
  87     <para>The following options are understood:</para>
  88
  89     <variablelist>
  90       <varlistentry>
  91         <term><option>--ready</option></term>
  92
  93         <listitem><para>Inform the init system about service start-up
  94         completion. This is equivalent to <command>systemd-notify
  95         READY=1</command>. For details about the semantics of this
  96         option see
  97         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
  98       </varlistentry>
  99
 100       <varlistentry>
 101         <term><option>--pid=</option></term>
 102
 103         <listitem><para>Inform the init system about the main PID of
 104         the daemon. Takes a PID as argument. If the argument is
 105         omitted, the PID of the process that invoked
 106         <command>systemd-notify</command> is used. This is equivalent
 107         to <command>systemd-notify MAINPID=$PID</command>. For details
 108         about the semantics of this option see
 109         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
 110       </varlistentry>
 111
 112       <varlistentry>
 113         <term><option>--uid=</option><replaceable>USER</replaceable></term>
 114
 115         <listitem><para>Set the user ID to send the notification from. Takes a UNIX user name or numeric UID. When
 116         specified the notification message will be sent with the specified UID as sender, in place of the user the
 117         command was invoked as. This option requires sufficient privileges in order to be able manipulate the user
 118         identity of the process.</para></listitem>
 119       </varlistentry>
 120
 121       <varlistentry>
 122         <term><option>--status=</option></term>
 123
 124         <listitem><para>Send a free-form status string for the daemon
 125         to the init systemd. This option takes the status string as
 126         argument. This is equivalent to <command>systemd-notify
 127         STATUS=…</command>. For details about the semantics of this
 128         option see
 129         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
 130       </varlistentry>
 131
 132       <varlistentry>
 133         <term><option>--booted</option></term>
 134
 135         <listitem><para>Returns 0 if the system was booted up with
 136         systemd, non-zero otherwise. If this option is passed, no
 137         message is sent. This option is hence unrelated to the other
 138         options. For details about the semantics of this option, see
 139         <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>. An
 140         alternate way to check for this state is to call
 141         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 142         with the <command>is-system-running</command> command. It will
 143         return <literal>offline</literal> if the system was not booted
 144         with systemd.  </para></listitem>
 145       </varlistentry>
 146
 147       <xi:include href="standard-options.xml" xpointer="help" />
 148       <xi:include href="standard-options.xml" xpointer="version" />
 149     </variablelist>
 150
 151   </refsect1>
 152
 153   <refsect1>
 154     <title>Exit status</title>
 155
 156     <para>On success, 0 is returned, a non-zero failure code
 157     otherwise.</para>
 158   </refsect1>
 159
 160   <refsect1>
 161     <title>Example</title>
 162
 163     <example>
 164       <title>Start-up Notification and Status Updates</title>
 165
 166       <para>A simple shell daemon that sends start-up notifications
 167       after having set up its communication channel. During runtime it
 168       sends further status updates to the init system:</para>
 169
 170       <programlisting>#!/bin/bash
 171
 172 mkfifo /tmp/waldo
 173 systemd-notify --ready --status="Waiting for data…"
 174
 175 while : ; do
 176         read a &lt; /tmp/waldo
 177         systemd-notify --status="Processing $a"
 178
 179         # Do something with $a …
 180
 181         systemd-notify --status="Waiting for data…"
 182 done</programlisting>
 183     </example>
 184   </refsect1>
 185
 186   <refsect1>
 187     <title>See Also</title>
 188     <para>
 189       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 190       <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 191       <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 192       <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 193       <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 194     </para>
 195   </refsect1>
 196
 197 </refentry>