<?xml version='1.0'?> <!--*-nxml-*--> <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> <!-- This file is part of systemd. Copyright 2010 Lennart Poettering systemd is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. systemd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with systemd; If not, see <http://www.gnu.org/licenses/>. --> <refentry id="sd_notify" xmlns:xi="http://www.w3.org/2001/XInclude"> <refentryinfo> <title>sd_notify</title> <productname>systemd</productname> <authorgroup> <author> <contrib>Developer</contrib> <firstname>Lennart</firstname> <surname>Poettering</surname> <email>lennart@poettering.net</email> </author> </authorgroup> </refentryinfo> <refmeta> <refentrytitle>sd_notify</refentrytitle> <manvolnum>3</manvolnum> </refmeta> <refnamediv> <refname>sd_notify</refname> <refname>sd_notifyf</refname> <refpurpose>Notify service manager about start-up completion and other service status changes</refpurpose> </refnamediv> <refsynopsisdiv> <funcsynopsis> <funcsynopsisinfo>#include <systemd/sd-daemon.h></funcsynopsisinfo> <funcprototype> <funcdef>int <function>sd_notify</function></funcdef> <paramdef>int <parameter>unset_environment</parameter></paramdef> <paramdef>const char *<parameter>state</parameter></paramdef> </funcprototype> <funcprototype> <funcdef>int <function>sd_notifyf</function></funcdef> <paramdef>int <parameter>unset_environment</parameter></paramdef> <paramdef>const char *<parameter>format</parameter></paramdef> <paramdef>...</paramdef> </funcprototype> </funcsynopsis> </refsynopsisdiv> <refsect1> <title>Description</title> <para><function>sd_notify()</function> may be called by a service to notify the service manager about state changes. It can be used to send arbitrary information, encoded in an environment-block-like string. Most importantly it can be used for start-up completion notification.</para> <para>If the <parameter>unset_environment</parameter> parameter is non-zero, <function>sd_notify()</function> will unset the <varname>$NOTIFY_SOCKET</varname> environment variable before returning (regardless of whether the function call itself succeeded or not). Further calls to <function>sd_notify()</function> will then fail, but the variable is no longer inherited by child processes.</para> <para>The <parameter>state</parameter> parameter should contain a newline-separated list of variable assignments, similar in style to an environment block. A trailing newline is implied if none is specified. The string may contain any kind of variable assignments, but the following shall be considered well-known:</para> <variablelist> <varlistentry> <term>READY=1</term> <listitem><para>Tells the service manager that service startup is finished. This is only used by systemd if the service definition file has Type=notify set. Since there is little value in signaling non-readiness, the only value services should send is <literal>READY=1</literal> (i.e. <literal>READY=0</literal> is not defined).</para></listitem> </varlistentry> <varlistentry> <term>RELOADING=1</term> <listitem><para>Tells the service manager that the service is reloading its configuration. This is useful to allow the service manager to track the service's internal state, and present it to the user. Note that a service that sends this notification must also send a <literal>READY=1</literal> notification when it completed reloading its configuration.</para></listitem> </varlistentry> <varlistentry> <term>STOPPING=1</term> <listitem><para>Tells the service manager that the service is beginning its shutdown. This is useful to allow the service manager to track the service's internal state, and present it to the user.</para></listitem> </varlistentry> <varlistentry> <term>STATUS=...</term> <listitem><para>Passes a single-line UTF-8 status string back to the service manager that describes the service state. This is free-form and can be used for various purposes: general state feedback, fsck-like programs could pass completion percentages and failing programs could pass a human readable error message. Example: <literal>STATUS=Completed 66% of file system check...</literal></para></listitem> </varlistentry> <varlistentry> <term>ERRNO=...</term> <listitem><para>If a service fails, the errno-style error code, formatted as string. Example: <literal>ERRNO=2</literal> for ENOENT.</para></listitem> </varlistentry> <varlistentry> <term>BUSERROR=...</term> <listitem><para>If a service fails, the D-Bus error-style error code. Example: <literal>BUSERROR=org.freedesktop.DBus.Error.TimedOut</literal></para></listitem> </varlistentry> <varlistentry> <term>MAINPID=...</term> <listitem><para>The main pid of the service, in case the service manager did not fork off the process itself. Example: <literal>MAINPID=4711</literal></para></listitem> </varlistentry> <varlistentry> <term>WATCHDOG=1</term> <listitem><para>Tells systemd to update the watchdog timestamp. This is the keep-alive ping that services need to issue in regular intervals if <varname>WatchdogSec=</varname> is enabled for it. See <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> for details. It is recommended to send this message if the <varname>$WATCHDOG_PID</varname> environment variable has been set to the PID of the service process, in every half the time interval that is specified in the <varname>$WATCHDOG_USEC</varname> environment variable. See <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry> for details.</para></listitem> </varlistentry> </variablelist> <para>It is recommended to prefix variable names that are not shown in the list above with <varname>X_</varname> to avoid namespace clashes.</para> <para>Note that systemd will accept status data sent from a service only if the <varname>NotifyAccess=</varname> option is correctly set in the service definition file. See <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry> for details.</para> <para><function>sd_notifyf()</function> is similar to <function>sd_notify()</function> but takes a <function>printf()</function>-like format string plus arguments.</para> </refsect1> <refsect1> <title>Return Value</title> <para>On failure, these calls return a negative errno-style error code. If <varname>$NOTIFY_SOCKET</varname> was not set and hence no status data could be sent, 0 is returned. If the status was sent, these functions return with a positive return value. In order to support both, init systems that implement this scheme and those which do not, it is generally recommended to ignore the return value of this call.</para> </refsect1> <refsect1> <title>Notes</title> <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/> <para>Internally, these functions send a single datagram with the state string as payload to the <constant>AF_UNIX</constant> socket referenced in the <varname>$NOTIFY_SOCKET</varname> environment variable. If the first character of <varname>$NOTIFY_SOCKET</varname> is <literal>@</literal>, the string is understood as Linux abstract namespace socket. The datagram is accompanied by the process credentials of the sending service, using SCM_CREDENTIALS.</para> </refsect1> <refsect1> <title>Environment</title> <variablelist class='environment-variables'> <varlistentry> <term><varname>$NOTIFY_SOCKET</varname></term> <listitem><para>Set by the service manager for supervised processes for status and start-up completion notification. This environment variable specifies the socket <function>sd_notify()</function> talks to. See above for details.</para></listitem> </varlistentry> </variablelist> </refsect1> <refsect1> <title>Examples</title> <example> <title>Start-up Notification</title> <para>When a service finished starting up, it might issue the following call to notify the service manager:</para> <programlisting>sd_notify(0, "READY=1");</programlisting> </example> <example> <title>Extended Start-up Notification</title> <para>A service could send the following after completing initialization:</para> <programlisting>sd_notifyf(0, "READY=1\n" "STATUS=Processing requests...\n" "MAINPID=%lu", (unsigned long) getpid());</programlisting> </example> <example> <title>Error Cause Notification</title> <para>A service could send the following shortly before exiting, on failure</para> <programlisting>sd_notifyf(0, "STATUS=Failed to start up: %s\n" "ERRNO=%i", strerror(errno), errno);</programlisting> </example> </refsect1> <refsect1> <title>See Also</title> <para> <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>, <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>, <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry> </para> </refsect1> </refentry>