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 2021-04-01.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2021-04-01.)  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 248                                            SYSTEMD-NOTIFY(1)

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