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.
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:
.RS 4
#!/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
.RE
systemd(1), systemctl(1), systemd.unit(5), systemd.service(5), sd_notify(3), sd_booted(3)