SYSTEMD-NOTIFY(1) systemd-notify SYSTEMD-NOTIFY(1)
NAME
systemd-notify - Notify service manager about start-up completion and
other daemon status changes
SYNOPSIS
systemd-notify [OPTIONS...] [VARIABLE=VALUE...]
systemd-notify [--exec] [OPTIONS...] [VARIABLE=VALUE...] [;]
[CMDLINE...]
DESCRIPTION
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.
OPTIONS
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).
Added in version 253.
--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).
Added in version 253.
--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.
Added in version 237.
--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.
Added in version 246.
--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 "\;".
Added in version 254.
--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
Added in version 254.
--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.
Added in version 254.
-h, --help
Print a short help text and exit.
--version
Print a short version string and exit.
EXIT STATUS
On success, 0 is returned, a non-zero failure code otherwise.
EXAMPLE
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
SEE ALSO
systemd(1), systemctl(1), systemd.unit(5), systemd.service(5),
sd_notify(3), sd_booted(3)
systemd 257.9 SYSTEMD-NOTIFY(1)
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