systemd-notify(1) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | EXAMPLE | SEE ALSO | COLOPHON

SYSTEMD-NOTIFY(1)              systemd-notify              SYSTEMD-NOTIFY(1)

NAME         top

       systemd-notify - Notify service manager about start-up completion and
       other daemon status changes

SYNOPSIS         top

       systemd-notify [OPTIONS...] [VARIABLE=VALUE...]

DESCRIPTION         top

       systemd-notify may be called by daemon scripts to notify the init
       system about status changes. It can be used to send arbitrary
       information, encoded in an environment-block-like list of strings.
       Most importantly, it can be used for start-up completion
       notification.

       This is mostly just a wrapper around sd_notify() and makes this
       functionality available to shell scripts. For details see
       sd_notify(3).

       The command line may carry a list of environment variables to send as
       part of the status update.

       Note that systemd will refuse reception of status updates from this
       command unless NotifyAccess= is set for the service unit this command
       is called from.

       Note that sd_notify() 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 NotifyAccess=main or NotifyAccess=exec.
       Conversely, if an auxiliary process of the unit sends an sd_notify()
       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 NotifyAccess=all is set for it. When --no-block is used,
       all synchronization for reception of notifications is disabled, and
       hence the aforementioned race may occur if the invoking process is
       not the service manager or spawned by the service manager.

       Hence, systemd-notify will first attempt to invoke sd_notify()
       pretending to have the PID of the invoking process. This will only
       succeed when invoked with sufficient privileges. On failure, it will
       then fall back to invoking it under its own PID. This behaviour is
       useful in order that when the tool is invoked from a shell script the
       shell process — and not the systemd-notify process — appears as
       sender of the message, which in turn is helpful if the shell process
       is the main process of a service, due to the limitations of
       NotifyAccess=all. Use the --pid= switch to tweak this behaviour.

OPTIONS         top

       The following options are understood:

       --ready
           Inform the init system about service start-up completion. This is
           equivalent to systemd-notify READY=1. For details about the
           semantics of this option see sd_notify(3).

       --pid=
           Inform the service manager about the main PID of the daemon.
           Takes a PID as argument. If the argument is specified as "auto"
           or omitted, the PID of the process that invoked systemd-notify is
           used, except if that's the service manager. If the argument is
           specified as "self", the PID of the systemd-notify command itself
           is used, and if "parent" is specified the calling process' PID is
           used — even if it is the service manager. This is equivalent to
           systemd-notify MAINPID=$PID. For details about the semantics of
           this option see sd_notify(3).

       --uid=USER
           Set the user ID to send the notification from. Takes a UNIX user
           name or numeric UID. When specified the notification message will
           be sent with the specified UID as sender, in place of the user
           the command was invoked as. This option requires sufficient
           privileges in order to be able manipulate the user identity of
           the process.

       --status=
           Send a free-form status string for the daemon to the init
           systemd. This option takes the status string as argument. This is
           equivalent to systemd-notify STATUS=.... For details about the
           semantics of this option see sd_notify(3).

       --booted
           Returns 0 if the system was booted up with systemd, non-zero
           otherwise. If this option is passed, no message is sent. This
           option is hence unrelated to the other options. For details about
           the semantics of this option, see sd_booted(3). An alternate way
           to check for this state is to call systemctl(1) with the
           is-system-running command. It will return "offline" if the system
           was not booted with systemd.

       --no-block
           Do not synchronously wait for the requested operation to finish.
           Use of this option is only recommended when systemd-notify is
           spawned by the service manager, or when the invoking process is
           directly spawned by the service manager and has enough privileges
           to allow systemd-notify to send the notification on its behalf.
           Sending notifications with this option set is prone to race
           conditions in all other cases.

       -h, --help
           Print a short help text and exit.

       --version
           Print a short version string and exit.

EXIT STATUS         top

       On success, 0 is returned, a non-zero failure code otherwise.

EXAMPLE         top

       Example 1. Start-up Notification and Status Updates

       A simple shell daemon that sends start-up notifications after having
       set up its communication channel. During runtime it sends further
       status updates to the init system:

           #!/bin/bash

           mkfifo /tmp/waldo
           systemd-notify --ready --status="Waiting for data..."

           while : ; do
                   read a < /tmp/waldo
                   systemd-notify --status="Processing $a"

                   # Do something with $a ...

                   systemd-notify --status="Waiting for data..."
           done

SEE ALSO         top

       systemd(1), systemctl(1), systemd.unit(5), sd_notify(3), sd_booted(3)

COLOPHON         top

       This page is part of the systemd (systemd system and service manager)
       project.  Information about the project can be found at 
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have a bug
       report for this manual page, see
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.  This
       page was obtained from the project's upstream Git repository
       ⟨https://github.com/systemd/systemd.git⟩ on 2020-07-14.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2020-07-14.)  If you discover any rendering problems in
       this HTML version of the page, or you believe there is a better or
       more up-to-date source for the page, or you have corrections or
       improvements to the information in this COLOPHON (which is not part
       of the original manual page), send a mail to man-pages@man7.org

systemd 246                                                SYSTEMD-NOTIFY(1)

Pages that refer to this page: init(1)systemd(1)30-systemd-environment-d-generator(7)systemd.directives(7)systemd.index(7)