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 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.

       wdmd will exit if a watchdog driver is not 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.

       (Other  test  sources  such  as  scripts  executed  each test interval may be added in the
       future.)

OPTIONS

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

       -H num Enable (1) or disable (0)  high  priority  features  such  as  realtime  scheduling
              priority and mlockall.
              Default 1.

                                            2011-08-01                                    WDMD(8)