WDMD(8)WDMD(8)NAMEwdmd - watchdog multiplexing daemon
SYNOPSISwdmd [OPTIONS]
DESCRIPTION
This daemon opens /dev/watchdog and allows multiple independent sources
to detmermine whether each KEEPALIVE is done. Every test interval (10
seconds), the daemon tests each source. If any test fails, the
KEEPALIVE is not done. In a standard configuration, the watchdog timer
will reset the system if no KEEPALIVE is done for 60 seconds ("fire
timeout"). This means that if a single test fails 5-6 times in row,
the watchdog will fire and reset the system. With multiple test
sources, fewer separate failures back to back can also cause a reset,
e.g.
T seconds, P pass, F fail
T00: test1 P, test2 P, test3 P: KEEPALIVE done
T10: test1 F, test2 F, test3 P: KEEPALIVE skipped
T20: test1 F, test2 P, test3 P: KEEPALIVE skipped
T30: test1 P, test2 F, test3 P: KEEPALIVE skipped
T40: test1 P, test2 P, test3 F: KEEPALIVE skipped
T50: test1 F, test2 F, test3 P: KEEPALIVE skipped
T60: test1 P, test2 F, test3 P: KEEPALIVE skipped
T60: watchdog fires, system resets
(Depending on timings, the system may be reset sometime shortly before
T60, and the tests at T60 would not be run.)
A crucial aspect to the design and function of wdmd is that if any sin‐
gle source does not pass tests for the fire timeout, the watchdog is
guaranteed to fire, regardless of whether other sources on the system
have passed or failed. A spurious reset due to the combined effects of
multiple failing tests as shown above, is an accepted side effect.
The wdmd init script will load the softdog module if no other watchdog
module has been loaded.
wdmd cannot be used on the system with any other program that needs to
open /dev/watchdog, e.g. watchdog(8).
Test Source: clients
Using libwdmd, programs connect to wdmd via a unix socket, and send
regular messages to wdmd to update an expiry time for their connection.
Every test interval, wdmd will check if the expiry time for a connec‐
tion has been reached. If so, the test for that client fails.
Test Source: scripts
wdmd will run scripts from a designated directory every test interval.
If a script exits with 0, the test is considered a success, otherwise a
failure. If a script does not exit by the end of the test interval, it
is considered a failure.
OPTIONS--version, -V
Print version.
--help, -h
Print usage.
--dump, -d
Print debug information from the daemon.
-D
Enable debugging to stderr and don't fork.
-H 0|1
Enable (1) or disable (0) high priority features such as real‐
time
scheduling priority and mlockall.
-G name
Group ownership for the socket.
-S 0|1
Enable (1) or disable (0) script tests.
-s path
Path to scripts dir.
-k num
Kill unfinished scripts after num seconds.
2011-08-01 WDMD(8)
