man/systemd-notify.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7 -->
   8
   9 <refentry id="systemd-notify"
  10     xmlns:xi="http://www.w3.org/2001/XInclude">
  11
  12   <refentryinfo>
  13     <title>systemd-notify</title>
  14     <productname>systemd</productname>
  15   </refentryinfo>
  16
  17   <refmeta>
  18     <refentrytitle>systemd-notify</refentrytitle>
  19     <manvolnum>1</manvolnum>
  20   </refmeta>
  21
  22   <refnamediv>
  23     <refname>systemd-notify</refname>
  24     <refpurpose>Notify service manager about start-up completion and other daemon status changes</refpurpose>
  25   </refnamediv>
  26
  27   <refsynopsisdiv>
  28     <cmdsynopsis>
  29       <command>systemd-notify <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="opt" rep="repeat">VARIABLE=VALUE</arg></command>
  30     </cmdsynopsis>
  31   </refsynopsisdiv>
  32
  33   <refsect1>
  34     <title>Description</title>
  35
  36     <para><command>systemd-notify</command> may be called by daemon
  37     scripts to notify the init system about status changes. It can be
  38     used to send arbitrary information, encoded in an
  39     environment-block-like list of strings. Most importantly, it can be
  40     used for start-up completion notification.</para>
  41
  42     <para>This is mostly just a wrapper around
  43     <function>sd_notify()</function> and makes this functionality
  44     available to shell scripts. For details see
  45     <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  46     </para>
  47
  48     <para>The command line may carry a list of environment variables
  49     to send as part of the status update.</para>
  50
  51     <para>Note that systemd will refuse reception of status updates from this command unless
  52     <varname>NotifyAccess=</varname> is set for the service unit this command is called from.</para>
  53
  54     <para>Note that <function>sd_notify()</function> notifications may be attributed to units correctly only if either
  55     the sending process is still around at the time PID 1 processes the message, or if the sending process is
  56     explicitly runtime-tracked by the service manager. The latter is the case if the service manager originally forked
  57     off the process, i.e. on all processes that match <varname>NotifyAccess=</varname><option>main</option> or
  58     <varname>NotifyAccess=</varname><option>exec</option>. Conversely, if an auxiliary process of the unit sends an
  59     <function>sd_notify()</function> message and immediately exits, the service manager might not be able to properly
  60     attribute the message to the unit, and thus will ignore it, even if
  61     <varname>NotifyAccess=</varname><option>all</option> is set for it.</para>
  62
  63     <para><command>systemd-notify</command> will first attempt to invoke <function>sd_notify()</function> pretending to
  64     have the PID of the invoking process. This will only succeed when invoked with sufficient privileges. On failure,
  65     it will then fall back to invoking it under its own PID. This behaviour is useful in order that when the tool is
  66     invoked from a shell script the shell process — and not the <command>systemd-notify</command> process — appears as
  67     sender of the message, which in turn is helpful if the shell process is the main process of a service, due to the
  68     limitations of <varname>NotifyAccess=</varname><option>all</option> described above.</para>
  69   </refsect1>
  70
  71   <refsect1>
  72     <title>Options</title>
  73
  74     <para>The following options are understood:</para>
  75
  76     <variablelist>
  77       <varlistentry>
  78         <term><option>--ready</option></term>
  79
  80         <listitem><para>Inform the init system about service start-up
  81         completion. This is equivalent to <command>systemd-notify
  82         READY=1</command>. For details about the semantics of this
  83         option see
  84         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
  85       </varlistentry>
  86
  87       <varlistentry>
  88         <term><option>--pid=</option></term>
  89
  90         <listitem><para>Inform the init system about the main PID of
  91         the daemon. Takes a PID as argument. If the argument is
  92         omitted, the PID of the process that invoked
  93         <command>systemd-notify</command> is used. This is equivalent
  94         to <command>systemd-notify MAINPID=$PID</command>. For details
  95         about the semantics of this option see
  96         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
  97       </varlistentry>
  98
  99       <varlistentry>
 100         <term><option>--uid=</option><replaceable>USER</replaceable></term>
 101
 102         <listitem><para>Set the user ID to send the notification from. Takes a UNIX user name or numeric UID. When
 103         specified the notification message will be sent with the specified UID as sender, in place of the user the
 104         command was invoked as. This option requires sufficient privileges in order to be able manipulate the user
 105         identity of the process.</para></listitem>
 106       </varlistentry>
 107
 108       <varlistentry>
 109         <term><option>--status=</option></term>
 110
 111         <listitem><para>Send a free-form status string for the daemon
 112         to the init systemd. This option takes the status string as
 113         argument. This is equivalent to <command>systemd-notify
 114         STATUS=…</command>. For details about the semantics of this
 115         option see
 116         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
 117       </varlistentry>
 118
 119       <varlistentry>
 120         <term><option>--booted</option></term>
 121
 122         <listitem><para>Returns 0 if the system was booted up with
 123         systemd, non-zero otherwise. If this option is passed, no
 124         message is sent. This option is hence unrelated to the other
 125         options. For details about the semantics of this option, see
 126         <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>. An
 127         alternate way to check for this state is to call
 128         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 129         with the <command>is-system-running</command> command. It will
 130         return <literal>offline</literal> if the system was not booted
 131         with systemd.  </para></listitem>
 132       </varlistentry>
 133
 134       <xi:include href="standard-options.xml" xpointer="help" />
 135       <xi:include href="standard-options.xml" xpointer="version" />
 136     </variablelist>
 137
 138   </refsect1>
 139
 140   <refsect1>
 141     <title>Exit status</title>
 142
 143     <para>On success, 0 is returned, a non-zero failure code
 144     otherwise.</para>
 145   </refsect1>
 146
 147   <refsect1>
 148     <title>Example</title>
 149
 150     <example>
 151       <title>Start-up Notification and Status Updates</title>
 152
 153       <para>A simple shell daemon that sends start-up notifications
 154       after having set up its communication channel. During runtime it
 155       sends further status updates to the init system:</para>
 156
 157       <programlisting>#!/bin/bash
 158
 159 mkfifo /tmp/waldo
 160 systemd-notify --ready --status="Waiting for data…"
 161
 162 while : ; do
 163         read a &lt; /tmp/waldo
 164         systemd-notify --status="Processing $a"
 165
 166         # Do something with $a …
 167
 168         systemd-notify --status="Waiting for data…"
 169 done</programlisting>
 170     </example>
 171   </refsect1>
 172
 173   <refsect1>
 174     <title>See Also</title>
 175     <para>
 176       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 177       <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 178       <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 179       <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 180       <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 181     </para>
 182   </refsect1>
 183
 184 </refentry>