man/systemd-notify.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="systemd-notify"
   7     xmlns:xi="http://www.w3.org/2001/XInclude">
   8
   9   <refentryinfo>
  10     <title>systemd-notify</title>
  11     <productname>systemd</productname>
  12   </refentryinfo>
  13
  14   <refmeta>
  15     <refentrytitle>systemd-notify</refentrytitle>
  16     <manvolnum>1</manvolnum>
  17   </refmeta>
  18
  19   <refnamediv>
  20     <refname>systemd-notify</refname>
  21     <refpurpose>Notify service manager about start-up completion and other daemon status changes</refpurpose>
  22   </refnamediv>
  23
  24   <refsynopsisdiv>
  25     <cmdsynopsis>
  26       <command>systemd-notify <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="opt" rep="repeat">VARIABLE=VALUE</arg></command>
  27     </cmdsynopsis>
  28   </refsynopsisdiv>
  29
  30   <refsect1>
  31     <title>Description</title>
  32
  33     <para><command>systemd-notify</command> may be called by daemon
  34     scripts to notify the init system about status changes. It can be
  35     used to send arbitrary information, encoded in an
  36     environment-block-like list of strings. Most importantly, it can be
  37     used for start-up completion notification.</para>
  38
  39     <para>This is mostly just a wrapper around
  40     <function>sd_notify()</function> and makes this functionality
  41     available to shell scripts. For details see
  42     <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  43     </para>
  44
  45     <para>The command line may carry a list of environment variables
  46     to send as part of the status update.</para>
  47
  48     <para>Note that systemd will refuse reception of status updates from this command unless
  49     <varname>NotifyAccess=</varname> is set for the service unit this command is called from.</para>
  50
  51     <para>Note that <function>sd_notify()</function> notifications may be attributed to units correctly only if either
  52     the sending process is still around at the time PID 1 processes the message, or if the sending process is
  53     explicitly runtime-tracked by the service manager. The latter is the case if the service manager originally forked
  54     off the process, i.e. on all processes that match <varname>NotifyAccess=</varname><option>main</option> or
  55     <varname>NotifyAccess=</varname><option>exec</option>. Conversely, if an auxiliary process of the unit sends an
  56     <function>sd_notify()</function> message and immediately exits, the service manager might not be able to properly
  57     attribute the message to the unit, and thus will ignore it, even if
  58     <varname>NotifyAccess=</varname><option>all</option> is set for it.</para>
  59
  60     <para><command>systemd-notify</command> will first attempt to invoke <function>sd_notify()</function> pretending to
  61     have the PID of the invoking process. This will only succeed when invoked with sufficient privileges. On failure,
  62     it will then fall back to invoking it under its own PID. This behaviour is useful in order that when the tool is
  63     invoked from a shell script the shell process — and not the <command>systemd-notify</command> process — appears as
  64     sender of the message, which in turn is helpful if the shell process is the main process of a service, due to the
  65     limitations of <varname>NotifyAccess=</varname><option>all</option> described above.</para>
  66   </refsect1>
  67
  68   <refsect1>
  69     <title>Options</title>
  70
  71     <para>The following options are understood:</para>
  72
  73     <variablelist>
  74       <varlistentry>
  75         <term><option>--ready</option></term>
  76
  77         <listitem><para>Inform the init system about service start-up
  78         completion. This is equivalent to <command>systemd-notify
  79         READY=1</command>. For details about the semantics of this
  80         option see
  81         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
  82       </varlistentry>
  83
  84       <varlistentry>
  85         <term><option>--pid=</option></term>
  86
  87         <listitem><para>Inform the init system about the main PID of
  88         the daemon. Takes a PID as argument. If the argument is
  89         omitted, the PID of the process that invoked
  90         <command>systemd-notify</command> is used. This is equivalent
  91         to <command>systemd-notify MAINPID=$PID</command>. For details
  92         about the semantics of this option see
  93         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
  94       </varlistentry>
  95
  96       <varlistentry>
  97         <term><option>--uid=</option><replaceable>USER</replaceable></term>
  98
  99         <listitem><para>Set the user ID to send the notification from. Takes a UNIX user name or numeric UID. When
 100         specified the notification message will be sent with the specified UID as sender, in place of the user the
 101         command was invoked as. This option requires sufficient privileges in order to be able manipulate the user
 102         identity of the process.</para></listitem>
 103       </varlistentry>
 104
 105       <varlistentry>
 106         <term><option>--status=</option></term>
 107
 108         <listitem><para>Send a free-form status string for the daemon
 109         to the init systemd. This option takes the status string as
 110         argument. This is equivalent to <command>systemd-notify
 111         STATUS=…</command>. For details about the semantics of this
 112         option see
 113         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
 114       </varlistentry>
 115
 116       <varlistentry>
 117         <term><option>--booted</option></term>
 118
 119         <listitem><para>Returns 0 if the system was booted up with
 120         systemd, non-zero otherwise. If this option is passed, no
 121         message is sent. This option is hence unrelated to the other
 122         options. For details about the semantics of this option, see
 123         <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>. An
 124         alternate way to check for this state is to call
 125         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 126         with the <command>is-system-running</command> command. It will
 127         return <literal>offline</literal> if the system was not booted
 128         with systemd.  </para></listitem>
 129       </varlistentry>
 130
 131       <xi:include href="standard-options.xml" xpointer="help" />
 132       <xi:include href="standard-options.xml" xpointer="version" />
 133     </variablelist>
 134
 135   </refsect1>
 136
 137   <refsect1>
 138     <title>Exit status</title>
 139
 140     <para>On success, 0 is returned, a non-zero failure code
 141     otherwise.</para>
 142   </refsect1>
 143
 144   <refsect1>
 145     <title>Example</title>
 146
 147     <example>
 148       <title>Start-up Notification and Status Updates</title>
 149
 150       <para>A simple shell daemon that sends start-up notifications
 151       after having set up its communication channel. During runtime it
 152       sends further status updates to the init system:</para>
 153
 154       <programlisting>#!/bin/bash
 155
 156 mkfifo /tmp/waldo
 157 systemd-notify --ready --status="Waiting for data…"
 158
 159 while : ; do
 160         read a &lt; /tmp/waldo
 161         systemd-notify --status="Processing $a"
 162
 163         # Do something with $a …
 164
 165         systemd-notify --status="Waiting for data…"
 166 done</programlisting>
 167     </example>
 168   </refsect1>
 169
 170   <refsect1>
 171     <title>See Also</title>
 172     <para>
 173       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 174       <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 175       <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 176       <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 177       <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 178     </para>
 179   </refsect1>
 180
 181 </refentry>