mirror of
https://github.com/systemd/systemd.git
synced 2024-11-05 15:21:37 +03:00
bb31a4ac19
https://bugs.freedesktop.org/show_bug.cgi?id=55890
Fixed typos, serial comma, and removed "either" as there were more
than two options. Also did an extra rename of "system-shutdown"
to "systemd-shutdown" that was forgotten in commit
8bd3b8620c
320 lines
15 KiB
XML
320 lines
15 KiB
XML
<?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">
|
|
|
|
<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 daemon 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> shall be called
|
|
by a daemon to notify the init system about status
|
|
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
|
|
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 init system
|
|
that daemon startup is finished. This
|
|
is only used by systemd if the service
|
|
definition file has Type=notify
|
|
set. The passed argument is a boolean
|
|
"1" or "0". Since there is little
|
|
value in signaling non-readiness, the
|
|
only value daemons should send is
|
|
"READY=1".</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>STATUS=...</term>
|
|
|
|
<listitem><para>Passes a single-line
|
|
status string back to the init system
|
|
that describes the daemon 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:
|
|
"STATUS=Completed 66% of file system
|
|
check..."</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>ERRNO=...</term>
|
|
|
|
<listitem><para>If a daemon fails, the
|
|
errno-style error code, formatted as
|
|
string. Example: "ERRNO=2" for
|
|
ENOENT.</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>BUSERROR=...</term>
|
|
|
|
<listitem><para>If a daemon fails, the
|
|
D-Bus error-style error code. Example:
|
|
"BUSERROR=org.freedesktop.DBus.Error.TimedOut"</para></listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>MAINPID=...</term>
|
|
|
|
<listitem><para>The main pid of the
|
|
daemon, in case the init system did
|
|
not fork off the process
|
|
itself. Example:
|
|
"MAINPID=4711"</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_USEC=</varname>
|
|
environment variable has been set for
|
|
the service process, in every half the
|
|
time interval that is specified in the
|
|
variable.</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 daemon 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
|
|
don't, it is generally recommended to ignore the return
|
|
value of this call.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Notes</title>
|
|
|
|
<para>These functions are provided by the reference
|
|
implementation of APIs for new-style daemons and
|
|
distributed with the systemd package. The algorithms
|
|
they implement are simple, and can easily be
|
|
reimplemented in daemons if it is important to support
|
|
this interface without using the reference
|
|
implementation.</para>
|
|
|
|
<para>Internally, these functions send a single
|
|
datagram with the state string as payload to the
|
|
AF_UNIX socket referenced in the
|
|
<varname>$NOTIFY_SOCKET</varname> environment
|
|
variable. If the first character of
|
|
<varname>$NOTIFY_SOCKET</varname> is @ the string is
|
|
understood as Linux abstract namespace socket. The
|
|
datagram is accompanied by the process credentials of
|
|
the sending daemon, using SCM_CREDENTIALS.</para>
|
|
|
|
<para>For details about the algorithms check the
|
|
liberally licensed reference implementation sources:
|
|
<ulink url="http://cgit.freedesktop.org/systemd/systemd/plain/src/libsystemd-daemon/sd-daemon.c"/>
|
|
and <ulink
|
|
url="http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-daemon.h"/></para>
|
|
|
|
<para><function>sd_notify()</function> and
|
|
<function>sd_notifyf()</function> are implemented in
|
|
the reference implementation's
|
|
<filename>sd-daemon.c</filename> and
|
|
<filename>sd-daemon.h</filename> files. These
|
|
interfaces are available as shared library, which can
|
|
be compiled and linked to with the
|
|
<literal>libsystemd-daemon</literal>
|
|
<citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
|
|
file. Alternatively, applications consuming these APIs
|
|
may copy the implementation into their source tree. For
|
|
more details about the reference implementation see
|
|
<citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
|
|
|
|
<para>If the reference implementation is used as
|
|
drop-in files and -DDISABLE_SYSTEMD is set during
|
|
compilation these functions will always return 0 and
|
|
otherwise become a NOP.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Environment</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><varname>$NOTIFY_SOCKET</varname></term>
|
|
|
|
<listitem><para>Set by the init system
|
|
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 daemon finished starting up, it
|
|
might issue the following call to notify
|
|
the init system:</para>
|
|
|
|
<programlisting>sd_notify(0, "READY=1");</programlisting>
|
|
</example>
|
|
|
|
<example>
|
|
<title>Extended Start-up Notification</title>
|
|
|
|
<para>A daemon 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 daemon 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>
|
|
</para>
|
|
</refsect1>
|
|
|
|
</refentry>
|