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. --pid=auto is equivalent to systemd-notify
--pid=$PID. For details about the semantics of this option see
sd_notify(3).
systemd-notify will first attempt to invoke sd_notify()
pretending to have the PID specified with --pid=. This will only succeed when
invoked with sufficient privileges. On failure, it will then fall back to invoking it under its own
PID. Effectively, this means that a privileged invocation of systemd-notify --pid=
may circumvent NotifyAccess=main or NotifyAccess=exec
restrictions enforced for a service.
If this switch is used in an unprivileged 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(1) 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¶--version¶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