2018-07-03 00:15:39 +03:00
<?xml version='1.0'?>
2019-03-14 16:40:58 +03:00
< !DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
2015-06-18 20:47:44 +03:00
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
2020-11-09 07:23:58 +03:00
<!-- SPDX - License - Identifier: LGPL - 2.1 - or - later -->
2010-06-23 02:31:54 +04:00
2014-02-21 07:39:26 +04:00
<refentry id= "sd_notify"
2015-02-04 05:14:13 +03:00
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo >
<title > sd_notify</title>
<productname > systemd</productname>
</refentryinfo>
<refmeta >
<refentrytitle > sd_notify</refentrytitle>
<manvolnum > 3</manvolnum>
</refmeta>
<refnamediv >
<refname > sd_notify</refname>
<refname > sd_notifyf</refname>
<refname > sd_pid_notify</refname>
<refname > sd_pid_notifyf</refname>
<refname > sd_pid_notify_with_fds</refname>
2023-04-14 18:48:47 +03:00
<refname > sd_pid_notifyf_with_fds</refname>
2020-04-28 17:09:27 +03:00
<refname > sd_notify_barrier</refname>
2023-05-03 15:13:58 +03:00
<refname > sd_pid_notify_barrier</refname>
2015-02-04 05:14:13 +03:00
<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>
2016-12-12 01:01:07 +03:00
<paramdef > …</paramdef>
2015-02-04 05:14:13 +03:00
</funcprototype>
<funcprototype >
<funcdef > int <function > sd_pid_notify</function> </funcdef>
<paramdef > pid_t <parameter > pid</parameter> </paramdef>
<paramdef > int <parameter > unset_environment</parameter> </paramdef>
<paramdef > const char *<parameter > state</parameter> </paramdef>
</funcprototype>
<funcprototype >
<funcdef > int <function > sd_pid_notifyf</function> </funcdef>
<paramdef > pid_t <parameter > pid</parameter> </paramdef>
<paramdef > int <parameter > unset_environment</parameter> </paramdef>
<paramdef > const char *<parameter > format</parameter> </paramdef>
2016-12-12 01:01:07 +03:00
<paramdef > …</paramdef>
2015-02-04 05:14:13 +03:00
</funcprototype>
<funcprototype >
<funcdef > int <function > sd_pid_notify_with_fds</function> </funcdef>
<paramdef > pid_t <parameter > pid</parameter> </paramdef>
<paramdef > int <parameter > unset_environment</parameter> </paramdef>
<paramdef > const char *<parameter > state</parameter> </paramdef>
<paramdef > const int *<parameter > fds</parameter> </paramdef>
<paramdef > unsigned <parameter > n_fds</parameter> </paramdef>
</funcprototype>
2020-04-28 17:09:27 +03:00
2023-04-14 18:48:47 +03:00
<funcprototype >
<funcdef > int <function > sd_pid_notifyf_with_fds</function> </funcdef>
<paramdef > pid_t <parameter > pid</parameter> </paramdef>
<paramdef > int <parameter > unset_environment</parameter> </paramdef>
<paramdef > const int *<parameter > fds</parameter> </paramdef>
<paramdef > size_t <parameter > n_fds</parameter> </paramdef>
<paramdef > const char *<parameter > format</parameter> </paramdef>
<paramdef > …</paramdef>
</funcprototype>
2020-04-28 17:09:27 +03:00
<funcprototype >
<funcdef > int <function > sd_notify_barrier</function> </funcdef>
<paramdef > int <parameter > unset_environment</parameter> </paramdef>
<paramdef > uint64_t <parameter > timeout</parameter> </paramdef>
</funcprototype>
2023-05-03 15:13:58 +03:00
<funcprototype >
<funcdef > int <function > sd_pid_notify_barrier</function> </funcdef>
<paramdef > pid_t <parameter > pid</parameter> </paramdef>
<paramdef > int <parameter > unset_environment</parameter> </paramdef>
<paramdef > uint64_t <parameter > timeout</parameter> </paramdef>
</funcprototype>
2015-02-04 05:14:13 +03:00
</funcsynopsis>
</refsynopsisdiv>
<refsect1 >
<title > Description</title>
2023-04-12 11:29:14 +03:00
<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
2015-02-04 05:14:13 +03:00
well-known:</para>
<variablelist >
<varlistentry >
<term > READY=1</term>
2023-01-02 20:13:27 +03:00
<listitem > <para > Tells the service manager that service startup is finished, or the service finished
re-loading its configuration. This is only used by systemd if the service definition file has
<varname > Type=notify</varname> or <varname > Type=notify-reload</varname> 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>
2015-02-04 05:14:13 +03:00
</varlistentry>
<varlistentry >
<term > RELOADING=1</term>
2023-01-02 20:13:27 +03:00
<listitem > <para > Tells the service manager that the service is beginning to reload 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. Reloads the
service manager is notified about with this mechanisms are propagated in the same way as they are
when originally initiated through the service manager. This message is particularly relevant for
<varname > Type=notify-reload</varname> services, to inform the service manager that the request to
2023-08-22 19:52:36 +03:00
reload the service has been received and is now being processed.</para>
<xi:include href= "version-info.xml" xpointer= "v217" /> </listitem>
2023-01-02 20:13:27 +03:00
</varlistentry>
<varlistentry >
<term > MONOTONIC_USEC=…</term>
<listitem > <para > A field carrying the monotonic timestamp (as per
2023-06-14 11:13:08 +03:00
<constant > CLOCK_MONOTONIC</constant> ) formatted in decimal in μs, when the notification message was
2023-01-02 20:13:27 +03:00
generated by the client. This is typically used in combination with <literal > RELOADING=1</literal> ,
to allow the service manager to properly synchronize reload cycles. See
<citerefentry > <refentrytitle > systemd.service</refentrytitle> <manvolnum > 5</manvolnum> </citerefentry>
2023-08-22 19:52:36 +03:00
for details, specifically <literal > Type=notify-reload</literal> .</para>
<xi:include href= "version-info.xml" xpointer= "v253" /> </listitem>
2015-02-04 05:14:13 +03:00
</varlistentry>
<varlistentry >
<term > STOPPING=1</term>
2023-04-12 11:29:14 +03:00
<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
2023-08-22 19:52:36 +03:00
user.</para>
<xi:include href= "version-info.xml" xpointer= "v217" /> </listitem>
2015-02-04 05:14:13 +03:00
</varlistentry>
<varlistentry >
2016-12-12 01:01:07 +03:00
<term > STATUS=…</term>
2015-02-04 05:14:13 +03:00
2023-04-12 11:29:14 +03:00
<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
2023-08-22 19:52:36 +03:00
check…</literal> </para>
<xi:include href= "version-info.xml" xpointer= "v233" /> </listitem>
2015-02-04 05:14:13 +03:00
</varlistentry>
2023-01-26 12:44:03 +03:00
<varlistentry >
<term > NOTIFYACCESS=…</term>
2023-04-12 11:29:14 +03:00
<listitem > <para > Reset the access to the service status notification socket during runtime, overriding
<varname > NotifyAccess=</varname> setting in the service unit file. See
<citerefentry > <refentrytitle > systemd.service</refentrytitle> <manvolnum > 5</manvolnum> </citerefentry>
for details, specifically <literal > NotifyAccess=</literal> for a list of accepted
2023-08-22 19:52:36 +03:00
values.</para>
<xi:include href= "version-info.xml" xpointer= "v254" /> </listitem>
2023-01-26 12:44:03 +03:00
</varlistentry>
2015-02-04 05:14:13 +03:00
<varlistentry >
2016-12-12 01:01:07 +03:00
<term > ERRNO=…</term>
2015-02-04 05:14:13 +03:00
2023-04-12 11:29:14 +03:00
<listitem > <para > If a service fails, the errno-style error code, formatted as string. Example:
2023-08-22 19:52:36 +03:00
<literal > ERRNO=2</literal> for ENOENT.</para>
<xi:include href= "version-info.xml" xpointer= "v233" /> </listitem>
2015-02-04 05:14:13 +03:00
</varlistentry>
<varlistentry >
2016-12-12 01:01:07 +03:00
<term > BUSERROR=…</term>
2015-02-04 05:14:13 +03:00
2023-04-12 11:29:14 +03:00
<listitem > <para > If a service fails, the D-Bus error-style error code. Example:
2023-08-22 19:52:36 +03:00
<literal > BUSERROR=org.freedesktop.DBus.Error.TimedOut</literal> </para>
<xi:include href= "version-info.xml" xpointer= "v233" /> </listitem>
2015-02-04 05:14:13 +03:00
</varlistentry>
2023-04-12 12:56:00 +03:00
<varlistentry >
<term > EXIT_STATUS=…</term>
<listitem > <para > If a service exits, the return value of its <function > main()</function> function.
2023-08-22 19:52:36 +03:00
</para>
<xi:include href= "version-info.xml" xpointer= "v254" /> </listitem>
2023-04-12 12:56:00 +03:00
</varlistentry>
2015-02-04 05:14:13 +03:00
<varlistentry >
2016-12-12 01:01:07 +03:00
<term > MAINPID=…</term>
2015-02-04 05:14:13 +03:00
2023-04-12 11:29:14 +03:00
<listitem > <para > The main process ID (PID) of the service, in case the service manager did not fork
2023-08-22 19:52:36 +03:00
off the process itself. Example: <literal > MAINPID=4711</literal> </para>
<xi:include href= "version-info.xml" xpointer= "v233" /> </listitem>
2015-02-04 05:14:13 +03:00
</varlistentry>
<varlistentry >
<term > WATCHDOG=1</term>
2023-04-12 11:29:14 +03:00
<listitem > <para > Tells the service manager 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
2015-02-04 05:14:13 +03:00
<citerefentry > <refentrytitle > systemd.service</refentrytitle> <manvolnum > 5</manvolnum> </citerefentry>
for information how to enable this functionality and
<citerefentry > <refentrytitle > sd_watchdog_enabled</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry>
2023-04-12 11:29:14 +03:00
for the details of how the service can check whether the watchdog is enabled. </para> </listitem>
2015-02-04 05:14:13 +03:00
</varlistentry>
2018-03-07 16:16:49 +03:00
<varlistentry >
<term > WATCHDOG=trigger</term>
2023-04-12 11:29:14 +03:00
<listitem > <para > Tells the service manager that the service detected an internal error that should be
handled by the configured watchdog options. This will trigger the same behaviour as if
<varname > WatchdogSec=</varname> is enabled and the service did not send <literal > WATCHDOG=1</literal>
in time. Note that <varname > WatchdogSec=</varname> does not need to be enabled for
<literal > WATCHDOG=trigger</literal> to trigger the watchdog action. See
<citerefentry > <refentrytitle > systemd.service</refentrytitle> <manvolnum > 5</manvolnum> </citerefentry>
2023-08-22 19:52:36 +03:00
for information about the watchdog behavior. </para>
<xi:include href= "version-info.xml" xpointer= "v243" /> </listitem>
2018-03-07 16:16:49 +03:00
</varlistentry>
2017-11-13 20:06:09 +03:00
<varlistentry >
<term > WATCHDOG_USEC=…</term>
2023-04-12 11:29:14 +03:00
<listitem > <para > Reset <varname > watchdog_usec</varname> value during runtime. Notice that this is not
available when using <function > sd_event_set_watchdog()</function> or
<function > sd_watchdog_enabled()</function> . Example :
2023-08-22 19:52:36 +03:00
<literal > WATCHDOG_USEC=20000000</literal> </para>
<xi:include href= "version-info.xml" xpointer= "v233" /> </listitem>
2017-11-13 20:06:09 +03:00
</varlistentry>
2015-02-04 05:14:13 +03:00
2017-12-14 14:17:43 +03:00
<varlistentry >
<term > EXTEND_TIMEOUT_USEC=…</term>
<listitem > <para > Tells the service manager to extend the startup, runtime or shutdown service timeout
2023-04-12 11:29:14 +03:00
corresponding the current state. The value specified is a time in microseconds during which the
service must send a new message. A service timeout will occur if the message isn't received, but only
if the runtime of the current state is beyond the original maximum times of
<varname > TimeoutStartSec=</varname> , <varname > RuntimeMaxSec=</varname> , and
<varname > TimeoutStopSec=</varname> . See
<citerefentry > <refentrytitle > systemd.service</refentrytitle> <manvolnum > 5</manvolnum> </citerefentry>
2023-08-22 19:52:36 +03:00
for effects on the service timeouts.</para>
<xi:include href= "version-info.xml" xpointer= "v236" /> </listitem>
2017-12-14 14:17:43 +03:00
</varlistentry>
2015-02-04 05:14:13 +03:00
<varlistentry >
<term > FDSTORE=1</term>
2023-04-05 16:48:31 +03:00
<listitem > <para > Stores additional file descriptors in the service manager. File descriptors sent this
way will be maintained per-service by the service manager and will later be handed back using the
usual file descriptor passing logic at the next invocation of the service (e.g. when it is
restarted), see
<citerefentry > <refentrytitle > sd_listen_fds</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> .
This is useful for implementing services that can restart after an explicit request or a crash
without losing state. Any open sockets and other file descriptors which should not be closed during
the restart may be stored this way. Application state can either be serialized to a file in
<filename > /run/</filename> , or better, stored in a
<citerefentry > <refentrytitle > memfd_create</refentrytitle> <manvolnum > 2</manvolnum> </citerefentry>
memory file descriptor. Note that the service manager will accept messages for a service only if its
2017-06-21 00:30:30 +03:00
<varname > FileDescriptorStoreMax=</varname> setting is non-zero (defaults to zero, see
2020-04-08 21:19:30 +03:00
<citerefentry > <refentrytitle > systemd.service</refentrytitle> <manvolnum > 5</manvolnum> </citerefentry> ). If
<varname > FDPOLL=0</varname> is not set and the file descriptors sent are pollable (see
2023-04-05 16:48:31 +03:00
<citerefentry > <refentrytitle > epoll_ctl</refentrytitle> <manvolnum > 2</manvolnum> </citerefentry> ), then
any <constant > EPOLLHUP</constant> or <constant > EPOLLERR</constant> event seen on them will result in
their automatic removal from the store. Multiple arrays of file descriptors may be sent in separate
messages, in which case the arrays are combined. Note that the service manager removes duplicate
(pointing to the same object) file descriptors before passing them to the service. When a service is
stopped, its file descriptor store is discarded and all file descriptors in it are closed. Use
<function > sd_pid_notify_with_fds()</function> to send messages with <literal > FDSTORE=1</literal> , see
below. The service manager will set the <varname > $FDSTORE</varname> environment variable for services
2023-08-22 19:52:36 +03:00
that have the file descriptor store enabled.</para>
<xi:include href= "version-info.xml" xpointer= "v219" /> </listitem>
2015-02-04 05:14:13 +03:00
</varlistentry>
2017-11-13 20:26:04 +03:00
<varlistentry >
<term > FDSTOREREMOVE=1</term>
2023-04-12 11:29:14 +03:00
<listitem > <para > Removes file descriptors from the file descriptor store. This field needs to be
combined with <varname > FDNAME=</varname> to specify the name of the file descriptors to
2023-08-22 19:52:36 +03:00
remove.</para>
<xi:include href= "version-info.xml" xpointer= "v236" /> </listitem>
2017-11-13 20:26:04 +03:00
</varlistentry>
2015-10-04 18:36:19 +03:00
<varlistentry >
2016-12-12 01:01:07 +03:00
<term > FDNAME=…</term>
2015-10-04 18:36:19 +03:00
2023-04-12 11:29:14 +03:00
<listitem > <para > When used in combination with <varname > FDSTORE=1</varname> , specifies a name for the
submitted file descriptors. When used with <varname > FDSTOREREMOVE=1</varname> , specifies the name for
the file descriptors to remove. This name is passed to the service during activation, and may be
queried using
2015-10-04 18:36:19 +03:00
<citerefentry > <refentrytitle > sd_listen_fds_with_names</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> . File
2017-11-13 20:26:04 +03:00
descriptors submitted without this field set, will implicitly get the name <literal > stored</literal>
2023-04-12 11:29:14 +03:00
assigned. Note that, if multiple file descriptors are submitted at once, the specified name will be
assigned to all of them. In order to assign different names to submitted file descriptors, submit
them in separate invocations of <function > sd_pid_notify_with_fds()</function> . The name may consist
of arbitrary ASCII characters except control characters or <literal > :</literal> . It may not be longer
than 255 characters. If a submitted name does not follow these restrictions, it is
2023-08-22 19:52:36 +03:00
ignored.</para>
<xi:include href= "version-info.xml" xpointer= "v233" /> </listitem>
2015-10-04 18:36:19 +03:00
</varlistentry>
2020-04-08 21:19:30 +03:00
<varlistentry >
<term > FDPOLL=0</term>
2023-04-12 11:29:14 +03:00
<listitem > <para > When used in combination with <varname > FDSTORE=1</varname> , disables polling of the
stored file descriptors regardless of whether or not they are pollable. As this option disables
automatic cleanup of the stored file descriptors on EPOLLERR and EPOLLHUP, care must be taken to
ensure proper manual cleanup. Use of this option is not generally recommended except for when
automatic cleanup has unwanted behavior such as prematurely discarding file descriptors from the
2023-08-22 19:52:36 +03:00
store.</para>
<xi:include href= "version-info.xml" xpointer= "v246" /> </listitem>
2020-04-08 21:19:30 +03:00
</varlistentry>
2020-04-28 17:09:27 +03:00
<varlistentry >
<term > BARRIER=1</term>
2022-07-13 16:02:39 +03:00
<listitem > <para > Tells the service manager that the client is explicitly requesting synchronization by
means of closing the file descriptor sent with this command. The service manager guarantees that the
processing of a <varname > BARRIER=1</varname> command will only happen after all previous notification
messages sent before this command have been processed. Hence, this command accompanied with a single
file descriptor can be used to synchronize against reception of all previous status messages. Note
that this command cannot be mixed with other notifications, and has to be sent in a separate message
to the service manager, otherwise all assignments will be ignored. Note that sending 0 or more than 1
2023-08-22 19:52:36 +03:00
file descriptor with this command is a violation of the protocol.</para>
<xi:include href= "version-info.xml" xpointer= "v246" /> </listitem>
2020-04-28 17:09:27 +03:00
</varlistentry>
2015-02-04 05:14:13 +03:00
</variablelist>
2023-04-12 11:29:14 +03:00
<para > It is recommended to prefix variable names that are not listed 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 > Note that <function > sd_notify()</function> notifications may be attributed to units correctly only
if either the sending process is still around at the time PID 1 processes the message, or if the sending
process is explicitly runtime-tracked by the service manager. The latter is the case if the service
manager originally forked off the process, i.e. on all processes that match
<varname > NotifyAccess=</varname> <option > main</option> or
<varname > NotifyAccess=</varname> <option > exec</option> . Conversely, if an auxiliary process of the unit
sends an <function > sd_notify()</function> message and immediately exits, the service manager might not be
able to properly attribute the message to the unit, and thus will ignore it, even if
2017-02-06 15:49:44 +03:00
<varname > NotifyAccess=</varname> <option > all</option> is set for it.</para>
2023-04-14 18:48:47 +03:00
<para > Hence, to eliminate all race conditions involving lookup of the client's unit and attribution of
notifications to units correctly, <function > sd_notify_barrier()</function> may be used. This call acts as
a synchronization point and ensures all notifications sent before this call have been picked up by the
service manager when it returns successfully. Use of <function > sd_notify_barrier()</function> is needed
for clients which are not invoked by the service manager, otherwise this synchronization mechanism is
unnecessary for attribution of notifications to the unit.</para>
2020-04-28 17:09:27 +03:00
2023-04-12 11:29:14 +03:00
<para > <function > sd_notifyf()</function> is similar to <function > sd_notify()</function> but takes a
<function > printf()</function> -like format string plus arguments.</para>
<para > <function > sd_pid_notify()</function> and <function > sd_pid_notifyf()</function> are similar to
<function > sd_notify()</function> and <function > sd_notifyf()</function> but take a process ID (PID) to use
as originating PID for the message as first argument. This is useful to send notification messages on
behalf of other processes, provided the appropriate privileges are available. If the PID argument is
specified as 0, the process ID of the calling process is used, in which case the calls are fully
equivalent to <function > sd_notify()</function> and <function > sd_notifyf()</function> .</para>
2015-02-04 05:14:13 +03:00
2023-04-05 16:48:31 +03:00
<para > <function > sd_pid_notify_with_fds()</function> is similar to <function > sd_pid_notify()</function>
but takes an additional array of file descriptors. These file descriptors are sent along the notification
message to the service manager. This is particularly useful for sending <literal > FDSTORE=1</literal>
messages, as described above. The additional arguments are a pointer to the file descriptor array plus
the number of file descriptors in the array. If the number of file descriptors is passed as 0, the call
is fully equivalent to <function > sd_pid_notify()</function> , i.e. no file descriptors are passed. Note
that file descriptors sent to the service manager on a message without <literal > FDSTORE=1</literal> are
immediately closed on reception.</para>
2020-04-28 17:09:27 +03:00
2023-04-14 18:48:47 +03:00
<para > <function > sd_pid_notifyf_with_fds()</function> is a combination of
<function > sd_pid_notify_with_fds()</function> and <function > sd_notifyf()</function> , i.e. it accepts both
a PID and a set of file descriptors as input, and processes a format string to generate the state
string.</para>
2023-04-12 11:29:14 +03:00
<para > <function > sd_notify_barrier()</function> allows the caller to synchronize against reception of
previously sent notification messages and uses the <varname > BARRIER=1</varname> command. It takes a
relative <varname > timeout</varname> value in microseconds which is passed to
2020-04-28 17:09:27 +03:00
<citerefentry > <refentrytitle > ppoll</refentrytitle> <manvolnum > 2</manvolnum>
2023-05-03 15:13:58 +03:00
</citerefentry> . A value of UINT64_MAX is interpreted as infinite timeout.</para>
<para > <function > sd_pid_notify_barrier()</function> is just like <function > sd_notify_barrier()</function> ,
but allows specifying the originating PID for the notification message.</para>
2015-02-04 05:14:13 +03:00
</refsect1>
<refsect1 >
<title > Return Value</title>
2023-04-12 11:29:14 +03:00
<para > On failure, these calls return a negative errno-style error code. If
<varname > $NOTIFY_SOCKET</varname> was not set and hence no status message could be sent, 0 is
returned. If the status was sent, these functions return a positive value. In order to support both
service managers that implement this scheme and those which do not, it is generally recommended to ignore
the return value of this call. Note that the return value simply indicates whether the notification
message was enqueued properly, it does not reflect whether the message could be processed
2017-06-21 00:30:30 +03:00
successfully. Specifically, no error is returned when a file descriptor is attempted to be stored using
2023-04-12 11:29:14 +03:00
<varname > FDSTORE=1</varname> but the service is not actually configured to permit storing of file
descriptors (see above).</para>
2015-02-04 05:14:13 +03:00
</refsect1>
<refsect1 >
<title > Notes</title>
<xi:include href= "libsystemd-pkgconfig.xml" xpointer= "pkgconfig-text" />
2023-03-07 22:25:58 +03:00
<xi:include href= "threads-aware.xml" xpointer= "getenv" />
2015-02-04 05:14:13 +03:00
2023-04-12 11:29:14 +03:00
<para > These functions send a single datagram with the state string as payload to the socket referenced in
the <varname > $NOTIFY_SOCKET</varname> environment variable. If the first character of
<varname > $NOTIFY_SOCKET</varname> is <literal > /</literal> or <literal > @</literal> , the string is
understood as an <constant > AF_UNIX</constant> or Linux abstract namespace socket (respectively), and in
both cases the datagram is accompanied by the process credentials of the sending service, using
SCM_CREDENTIALS. If the string starts with <literal > vsock:</literal> then the string is understood as an
<constant > AF_VSOCK</constant> address, which is useful for hypervisors/VMMs or other processes on the
host to receive a notification when a virtual machine has finished booting. Note that in case the
hypervisor does not support <constant > SOCK_DGRAM</constant> over <constant > AF_VSOCK</constant> ,
<constant > SOCK_SEQPACKET</constant> will be used instead. The address should be in the form:
<literal > vsock:CID:PORT</literal> . Note that unlike other uses of vsock, the CID is mandatory and cannot
be <literal > VMADDR_CID_ANY</literal> . Note that PID1 will send the VSOCK packets from a privileged port
(i.e.: lower than 1024), as an attempt to address concerns that unprivileged processes in the guest might
try to send malicious notifications to the host, driving it to make destructive decisions based on
them.</para>
2015-02-04 05:14:13 +03:00
</refsect1>
<refsect1 >
<title > Environment</title>
<variablelist class= 'environment-variables' >
<varlistentry >
<term > <varname > $NOTIFY_SOCKET</varname> </term>
2023-04-12 11:29:14 +03:00
<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>
2015-02-04 05:14:13 +03:00
</varlistentry>
</variablelist>
</refsect1>
<refsect1 >
<title > Examples</title>
<example >
<title > Start-up Notification</title>
2023-04-12 11:29:14 +03:00
<para > When a service finished starting up, it might issue the following call to notify the service
manager:</para>
2015-02-04 05:14:13 +03:00
<programlisting > sd_notify(0, "READY=1");</programlisting>
</example>
<example >
<title > Extended Start-up Notification</title>
2023-04-12 11:29:14 +03:00
<para > A service could send the following after completing initialization:</para>
2015-02-04 05:14:13 +03:00
2023-01-22 19:51:30 +03:00
<programlisting >
sd_notifyf(0, "READY=1\n"
"STATUS=Processing requests…\n"
"MAINPID=%lu",
(unsigned long) getpid());</programlisting>
2015-02-04 05:14:13 +03:00
</example>
<example >
<title > Error Cause Notification</title>
<para > A service could send the following shortly before exiting, on failure:</para>
2023-01-22 19:51:30 +03:00
<programlisting >
sd_notifyf(0, "STATUS=Failed to start up: %s\n"
"ERRNO=%i",
strerror_r(errnum, (char[1024]){}, 1024),
errnum);</programlisting>
2015-02-04 05:14:13 +03:00
</example>
<example >
<title > Store a File Descriptor in the Service Manager</title>
2023-04-12 11:29:14 +03:00
<para > To store an open file descriptor in the service manager, in order to continue operation after a
service restart without losing state, use <literal > FDSTORE=1</literal> :</para>
2015-02-04 05:14:13 +03:00
2015-10-04 18:36:19 +03:00
<programlisting > sd_pid_notify_with_fds(0, 0, "FDSTORE=1\nFDNAME=foobar", & fd, 1);</programlisting>
2015-02-04 05:14:13 +03:00
</example>
2020-04-28 17:09:27 +03:00
<example >
<title > Eliminating race conditions</title>
2023-04-12 11:29:14 +03:00
<para > When the client sending the notifications is not spawned by the service manager, it may exit too
quickly and the service manager may fail to attribute them correctly to the unit. To prevent such
races, use <function > sd_notify_barrier()</function> to synchronize against reception of all
notifications sent before this call is made.</para>
2020-04-28 17:09:27 +03:00
2023-01-22 19:51:30 +03:00
<programlisting >
sd_notify(0, "READY=1");
/* set timeout to 5 seconds */
sd_notify_barrier(0, 5 * 1000000);
2020-04-28 17:09:27 +03:00
</programlisting>
</example>
2015-02-04 05:14:13 +03:00
</refsect1>
2023-09-04 15:46:35 +03:00
<refsect1 >
<title > History</title>
<para > <function > sd_pid_notify()</function> was added in version 219.</para>
<para > <function > sd_pid_notify_with_fds()</function> was added in version 219.</para>
<para > <function > sd_pid_notifyf()</function> was added in version 219.</para>
<para > <function > sd_notify_barrier()</function> was added in version 246.</para>
<para > <function > sd_pid_notify_barrier()</function> was added in version 254.</para>
<para > <function > sd_pid_notifyf_with_fds()</function> was added in version 254.</para>
</refsect1>
2015-02-04 05:14:13 +03:00
<refsect1 >
<title > See Also</title>
<para >
<citerefentry > <refentrytitle > systemd</refentrytitle> <manvolnum > 1</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd-daemon</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
2015-10-04 18:36:19 +03:00
<citerefentry > <refentrytitle > sd_listen_fds</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_listen_fds_with_names</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
<citerefentry > <refentrytitle > sd_watchdog_enabled</refentrytitle> <manvolnum > 3</manvolnum> </citerefentry> ,
2015-02-04 05:14:13 +03:00
<citerefentry > <refentrytitle > daemon</refentrytitle> <manvolnum > 7</manvolnum> </citerefentry> ,
2015-10-04 18:36:19 +03:00
<citerefentry > <refentrytitle > systemd.service</refentrytitle> <manvolnum > 5</manvolnum> </citerefentry>
2015-02-04 05:14:13 +03:00
</para>
</refsect1>
2010-06-23 02:31:54 +04:00
</refentry>