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)