sd_watchdog_enabled — Check whether the service manager expects watchdog keep-alive notifications from a service
sd_watchdog_enabled() may be called by
a service to detect whether the service manager expects regular
keep-alive watchdog notification events from it, and the timeout
after which the manager will act on the service if it did not get
such a notification.
variable is set, and the
is unset or set to the PID of the current process, the service
manager expects notifications from this process. The manager will
usually terminate a service when it does not get a notification
message within the specified time after startup and after each
previous message. It is recommended that a daemon sends a
keep-alive notification message to the service manager every half
of the time returned here. Notification messages may be sent with
with a message string of "
unset_environment parameter is
sd_watchdog_enabled() will unset
$WATCHDOG_PID environment variables before
returning (regardless of whether the function call itself
succeeded or not). Those variables are no longer inherited by
child processes. Further calls to
sd_watchdog_enabled() will also return with
usec parameter is non-NULL,
sd_watchdog_enabled() will write the timeout
in µs for the watchdog logic to it.
To enable service supervision with the watchdog logic, use
WatchdogSec= in service files. See
On failure, this call returns a negative errno-style error
code. If the service manager expects watchdog keep-alive
notification messages to be sent, > 0 is returned, otherwise 0
is returned. Only if the return value is > 0, the
usec parameter is valid after the
These APIs are implemented as a shared
library, which can be compiled and linked to with the
Internally, this functions parses the
$WATCHDOG_USEC environment variable. The call
will ignore these variables if
does not contain the PID of the current process, under the
assumption that in that case, the variables were set for a
different process further up the process tree.
Set by the system manager for supervised process for which watchdog support is enabled, and contains the PID of that process. See above for details.
Set by the system manager for supervised process for which watchdog support is enabled, and contains the watchdog timeout in µs See above for details.
The watchdog functionality and the
$WATCHDOG_USEC variable were added in
sd_watchdog_enabled() function was
added in systemd-209. Since that version, the
$WATCHDOG_PID variable is also set.