man/systemd-notify.xml

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  23
  24 <refentry id="systemd-notify"
  25     xmlns:xi="http://www.w3.org/2001/XInclude">
  26
  27   <refentryinfo>
  28     <title>systemd-notify</title>
  29     <productname>systemd</productname>
  30
  31     <authorgroup>
  32       <author>
  33         <contrib>Developer</contrib>
  34         <firstname>Lennart</firstname>
  35         <surname>Poettering</surname>
  36         <email>lennart@poettering.net</email>
  37       </author>
  38     </authorgroup>
  39   </refentryinfo>
  40
  41   <refmeta>
  42     <refentrytitle>systemd-notify</refentrytitle>
  43     <manvolnum>1</manvolnum>
  44   </refmeta>
  45
  46   <refnamediv>
  47     <refname>systemd-notify</refname>
  48     <refpurpose>Notify service manager about start-up completion and other daemon status changes</refpurpose>
  49   </refnamediv>
  50
  51   <refsynopsisdiv>
  52     <cmdsynopsis>
  53       <command>systemd-notify <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="opt" rep="repeat">VARIABLE=VALUE</arg></command>
  54     </cmdsynopsis>
  55   </refsynopsisdiv>
  56
  57   <refsect1>
  58     <title>Description</title>
  59
  60     <para><command>systemd-notify</command> may be called by daemon
  61     scripts to notify the init system about status changes. It can be
  62     used to send arbitrary information, encoded in an
  63     environment-block-like list of strings. Most importantly, it can be
  64     used for start-up completion notification.</para>
  65
  66     <para>This is mostly just a wrapper around
  67     <function>sd_notify()</function> and makes this functionality
  68     available to shell scripts. For details see
  69     <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  70     </para>
  71
  72     <para>The command line may carry a list of environment variables
  73     to send as part of the status update.</para>
  74
  75     <para>Note that systemd will refuse reception of status updates from this command unless
  76     <varname>NotifyAccess=</varname> is set for the service unit this command is called from.</para>
  77
  78     <para>Note that <function>sd_notify()</function> notifications may be attributed to units correctly only if either
  79     the sending process is still around at the time PID 1 processes the message, or if the sending process is
  80     explicitly runtime-tracked by the service manager. The latter is the case if the service manager originally forked
  81     off the process, i.e. on all processes that match <varname>NotifyAccess=</varname><option>main</option> or
  82     <varname>NotifyAccess=</varname><option>exec</option>. Conversely, if an auxiliary process of the unit sends an
  83     <function>sd_notify()</function> message and immediately exits, the service manager might not be able to properly
  84     attribute the message to the unit, and thus will ignore it, even if
  85     <varname>NotifyAccess=</varname><option>all</option> is set for it.</para>
  86
  87     <para><command>systemd-notify</command> will first attempt to invoke <function>sd_notify()</function> pretending to
  88     have the PID of the invoking process. This will only succeed when invoked with sufficient privileges. On failure,
  89     it will then fall back to invoking it under its own PID. This behaviour is useful in order that when the tool is
  90     invoked from a shell script the shell process — and not the <command>systemd-notify</command> process — appears as
  91     sender of the message, which in turn is helpful if the shell process is the main process of a service, due to the
  92     limitations of <varname>NotifyAccess=</varname><option>all</option> described above.</para>
  93   </refsect1>
  94
  95   <refsect1>
  96     <title>Options</title>
  97
  98     <para>The following options are understood:</para>
  99
 100     <variablelist>
 101       <varlistentry>
 102         <term><option>--ready</option></term>
 103
 104         <listitem><para>Inform the init system about service start-up
 105         completion. This is equivalent to <command>systemd-notify
 106         READY=1</command>. For details about the semantics of this
 107         option see
 108         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
 109       </varlistentry>
 110
 111       <varlistentry>
 112         <term><option>--pid=</option></term>
 113
 114         <listitem><para>Inform the init system about the main PID of
 115         the daemon. Takes a PID as argument. If the argument is
 116         omitted, the PID of the process that invoked
 117         <command>systemd-notify</command> is used. This is equivalent
 118         to <command>systemd-notify MAINPID=$PID</command>. For details
 119         about the semantics of this option see
 120         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
 121       </varlistentry>
 122
 123       <varlistentry>
 124         <term><option>--status=</option></term>
 125
 126         <listitem><para>Send a free-form status string for the daemon
 127         to the init systemd. This option takes the status string as
 128         argument. This is equivalent to <command>systemd-notify
 129         STATUS=…</command>. For details about the semantics of this
 130         option see
 131         <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
 132       </varlistentry>
 133
 134       <varlistentry>
 135         <term><option>--booted</option></term>
 136
 137         <listitem><para>Returns 0 if the system was booted up with
 138         systemd, non-zero otherwise. If this option is passed, no
 139         message is sent. This option is hence unrelated to the other
 140         options. For details about the semantics of this option, see
 141         <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>. An
 142         alternate way to check for this state is to call
 143         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 144         with the <command>is-system-running</command> command. It will
 145         return <literal>offline</literal> if the system was not booted
 146         with systemd.  </para></listitem>
 147       </varlistentry>
 148
 149       <xi:include href="standard-options.xml" xpointer="help" />
 150       <xi:include href="standard-options.xml" xpointer="version" />
 151     </variablelist>
 152
 153   </refsect1>
 154
 155   <refsect1>
 156     <title>Exit status</title>
 157
 158     <para>On success, 0 is returned, a non-zero failure code
 159     otherwise.</para>
 160   </refsect1>
 161
 162   <refsect1>
 163     <title>Example</title>
 164
 165     <example>
 166       <title>Start-up Notification and Status Updates</title>
 167
 168       <para>A simple shell daemon that sends start-up notifications
 169       after having set up its communication channel. During runtime it
 170       sends further status updates to the init system:</para>
 171
 172       <programlisting>#!/bin/bash
 173
 174 mkfifo /tmp/waldo
 175 systemd-notify --ready --status="Waiting for data…"
 176
 177 while : ; do
 178         read a &lt; /tmp/waldo
 179         systemd-notify --status="Processing $a"
 180
 181         # Do something with $a …
 182
 183         systemd-notify --status="Waiting for data…"
 184 done</programlisting>
 185     </example>
 186   </refsect1>
 187
 188   <refsect1>
 189     <title>See Also</title>
 190     <para>
 191       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 192       <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 193       <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 194       <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 195       <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 196     </para>
 197   </refsect1>
 198
 199 </refentry>