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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT STATUS | EXAMPLE | SEE ALSO | COLOPHON |
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SYSTEMD-NOTIFY(1) systemd-notify SYSTEMD-NOTIFY(1)
systemd-notify - Notify service manager about start-up completion
and other daemon status changes
systemd-notify [OPTIONS...] [VARIABLE=VALUE...]
systemd-notify --exec [OPTIONS...] [VARIABLE=VALUE...] ;
[CMDLINE...]
systemd-notify may be called by service scripts to notify the
invoking service manager 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 appropriately set for the
service unit this command is called from. See systemd.service(5)
for details.
Note that sd_notify() notifications may be attributed to units
correctly only if either the sending process is still around at
the time the service manager 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. To address this
systemd-notify will wait until the notification message has been
processed by the service manager. When --no-block is used, this
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.
systemd-notify will first attempt to invoke sd_notify()
pretending to have the PID of the parent process of
systemd-notify (i.e. 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.
The following options are understood:
--ready
Inform the invoking service manager about service start-up or
configuration reload completion. This is equivalent to
systemd-notify READY=1. For details about the semantics of
this option see sd_notify(3).
--reloading
Inform the invoking service manager about the beginning of a
configuration reload cycle. This is equivalent to
systemd-notify RELOADING=1 (but implicitly also sets a
MONOTONIC_USEC= field as required for Type=notify-reload
services, see systemd.service(5) for details). For details
about the semantics of this option see sd_notify(3).
--stopping
Inform the invoking service manager about the beginning of
the shutdown phase of the service. This is equivalent to
systemd-notify STOPPING=1. For details about the semantics of
this option see sd_notify(3).
--pid=
Inform the service manager about the main PID of the service.
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. The latter is equivalent to
systemd-notify MAINPID=$PID. For details about the semantics
of this option see sd_notify(3).
If this switch is used in an systemd-notify invocation from a
process that shall become the new main process of a service —
and which is not the process forked off by the service
manager (or the current main process) —, then it is essential
to set NotifyAccess=all in the service unit file, or
otherwise the notification will be ignored for security
reasons. See systemd.service(5) for details.
--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 human readable status string for the daemon
to the service manager. 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). This information is shown in systemctl(1)'s
status output, among other places.
--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.
--exec
If specified systemd-notify will execute another command line
after it completed its operation, replacing its own process.
If used, the list of assignments to include in the message
sent must be followed by a ";" character (as separate
argument), followed by the command line to execute. This
permits "chaining" of commands, i.e. issuing one operation,
followed immediately by another, without changing PIDs.
Note that many shells interpret ";" as their own separator
for command lines, hence when systemd-notify is invoked from
a shell the semicolon must usually be escaped as "\;".
--fd=
Send a file descriptor along with the notification message.
This is useful when invoked in services that have the
FileDescriptorStoreMax= setting enabled, see
systemd.service(5) for details. The specified file descriptor
must be passed to systemd-notify when invoked. This option
may be used multiple times to pass multiple file descriptors
in a single notification message.
To use this functionality from a bash shell, use an
expression like the following:
systemd-notify --fd=4 --fd=5 4</some/file 5</some/other/file
--fdname=
Set a name to assign to the file descriptors passed via --fd=
(see above). This controls the "FDNAME=" field. This setting
may only be specified once, and applies to all file
descriptors passed. Invoke this tool multiple times in case
multiple file descriptors with different file descriptor
names shall be submitted.
-h, --help
Print a short help text and exit.
--version
Print a short version string and exit.
On success, 0 is returned, a non-zero failure code otherwise.
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/sh
mkfifo /tmp/waldo
systemd-notify --ready --status="Waiting for data..."
while : ; do
read -r a < /tmp/waldo
systemd-notify --status="Processing $a"
# Do something with $a ...
systemd-notify --status="Waiting for data..."
done
systemd(1), systemctl(1), systemd.unit(5), systemd.service(5),
sd_notify(3), sd_booted(3)
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 2023-06-23. (At that
time, the date of the most recent commit that was found in the
repository was 2023-06-23.) 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 253 SYSTEMD-NOTIFY(1)
Pages that refer to this page: systemd(1), systemd.directives(7), systemd.index(7)
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HTML rendering created 2023-06-24 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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