wdmd

WDMD(8)                     System Manager's Manual                    WDMD(8)



NAME
       wdmd - watchdog multiplexing daemon


SYNOPSIS
       wdmd [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
       single 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
       connection 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.


       --probe, -p
                Print path of functional watchdog device.  Exit code 0
              indicates a
                functional device was found.  Exit code 1 indicates a
              functional device
                was not found.


       -D
                Enable debugging to stderr and don't fork.


       -H 0|1
                Enable (1) or disable (0) high priority features such as
              realtime
                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.


       -w path
                The path to the watchdog device to try first.





                                  2011-08-01                           WDMD(8)