Provided by: watchdog_5.11-1_amd64 bug

NAME

       watchdog - a software watchdog daemon

SYNOPSIS

       watchdog    [-F|--foreground]    [-f|--force]    [-c    filename|--config-file   filename]
       [-v|--verbose] [-s|--sync] [-b|--softboot] [-q|--no-action]

DESCRIPTION

       The Linux kernel can reset the system if serious  problems  are  detected.   This  can  be
       implemented  via  special watchdog hardware, or via a slightly less reliable software-only
       watchdog inside the kernel. Either way, there needs to be a daemon that tells  the  kernel
       the system is working fine. If the daemon stops doing that, the system is reset.

       watchdog is such a daemon. It opens /dev/watchdog, and keeps writing to it often enough to
       keep the kernel from resetting, at least once per minute. Each  write  delays  the  reboot
       time  another  minute.  After  a minute of inactivity the watchdog hardware will cause the
       reset. In the case of the software watchdog the ability to reboot will depend on the state
       of the machines and interrupts.

       The watchdog daemon can be stopped without causing a reboot if the device /dev/watchdog is
       closed correctly, unless your kernel is compiled with the CONFIG_WATCHDOG_NOWAYOUT  option
       enabled.

TESTS

       The watchdog daemon does several tests to check the system status:

       ·  Is the process table full?

       ·  Is there enough free memory?

       ·  Are some files accessible?

       ·  Have some files changed within a given interval?

       ·  Is the average work load too high?

       ·  Has a file table overflow occurred?

       ·  Is a process still running? The process is specified by a pid file.

       ·  Do some IP addresses answer to ping?

       ·  Do network interfaces receive traffic?

       ·  Is the temperature too high? (Temperature data not always available.)

       ·  Execute a user defined command to do arbitrary tests.

       ·  Execute  one or more test/repair commands found in /etc/watchdog.d.  These commands are
          called with the argument test or repair.

       If any of these checks fail watchdog will cause a shutdown.  Should  any  of  these  tests
       except  the  user defined binary last longer than one minute the machine will be rebooted,
       too.

OPTIONS

       Available command line options are the following:

       -v, --verbose
              Set verbose mode. Only implemented if compiled with SYSLOG feature. This mode  will
              log each several infos in LOG_DAEMON with priority LOG_INFO.  This is useful if you
              want to see exactly what happened until the watchdog rebooted the system. Currently
              it  logs  the  temperature (if available), the load average, the change date of the
              files it checks and how often it went to sleep.

       -s, --sync
              Try to synchronize the filesystem every time the process is awake.  Note  that  the
              system is rebooted if for any reason the synchronizing lasts longer than a minute.

       -b, --softboot
              Soft-boot  the system if an error occurs during the main loop, e.g. if a given file
              is not accessible via the stat(2) call. Note  that  this  does  not  apply  to  the
              opening  of  /dev/watchdog and /proc/loadavg, which are opened before the main loop
              starts.

       -F, --foreground
              Run in foreground mode, useful for running under systemd (for example).

       -f, --force
              Force the usage of the interval given or the maximal  load  average  given  in  the
              config file.

       -c config-file, --config-file config-file
              Use    config-file   as   the   configuration   file   instead   of   the   default
              /etc/watchdog.conf.

       -q, --no-action
              Do not reboot or halt the machine. This is for testing  purposes.  All  checks  are
              executed  and  the  results are logged as usual, but no action is taken.  Also your
              hardware card or the kernel software watchdog driver is  not  enabled.  Temperature
              checking is also disabled since this triggers the hardware watchdog on some cards.

FUNCTION

       After  watchdog  starts,  it  puts  itself  into  the background and then tries all checks
       specified in its configuration file in turn. Between each two tests it will write  to  the
       kernel  device  to  prevent a reset.  After finishing all tests watchdog goes to sleep for
       some time. The kernel drivers expects  a  write  to  the  watchdog  device  every  minute.
       Otherwise  the system will be reset. As a default watchdog will sleep for only 1 second so
       it triggers the device early enough.

       Under high system load watchdog might be swapped out of memory and may  fail  to  make  it
       back  in  in  time.  Under these circumstances the Linux kernel will reset the machine. To
       make sure you won't get unnecessary reboots make sure you have the variable  realtime  set
       to  yes in the configuration file watchdog.conf.  This adds real time support to watchdog:
       it will lock itself into memory and there should  be no problem even under the highest  of
       loads.

       On  system  running  out  of  memory  the kernel will try to free enough memory by killing
       process. The watchdog daemon itself is exempted from this so-called out-of-memory killer.

       Also you can specify a maximal allowed load average. Once this load average is reached the
       system  is  rebooted.  You may specify maximal load averages for 1 minute, 5 minutes or 15
       minutes. The default values is to disable this test. Be careful not to set this  parameter
       too  low.  To set a value less then the predefined minimal value of 2, you have to use the
       -f option.

       You can also specify a minimal amount of virtual memory you  want  to  have  available  as
       free.  As soon as more virtual memory is used action is taken by watchdog.  Note, however,
       that watchdog does not distinguish between different types of memory usage. It just checks
       for free virtual memory.

       If  you  have  a watchdog card with temperature sensor you can specify the maximal allowed
       temperature. Once this temperature is reached the system is halted. The default  value  is
       120.  There  is  no  unit  conversion so make sure you use the same unit as your hardware.
       watchdog will issue warnings once the temperature increases  90%,  95%  and  98%  of  this
       temperature.

       When using file mode watchdog will try to stat(2) the given files. Errors returned by stat
       will not cause a reboot. For a reboot the stat call has to last at least one minute.  This
       may  happen  if the file is located on an NFS mounted filesystem. If your system relies on
       an NFS mounted filesystem you might try this option.  However, in such  a  case  the  sync
       option may not work if the NFS server is not answering.

       watchdog  can  read  the  pid from a pid file and see whether the process still exists. If
       not, action is taken by watchdog.  So you can for instance restart the  server  from  your
       repair-binary.

       watchdog  will  try  periodically to fork itself to see whether the process table is full.
       This process will leave a zombie process until watchdog wakes up  again  and  catches  it;
       this is harmless, don't worry about it.

       In ping mode watchdog tries to ping the given IP addresses. These addresses do not have to
       be a single machine. It is possible to ping to a broadcast address instead to  see  if  at
       least one machine in a subnet is still living.

       Do  not  use this broadcast ping unless your MIS person a) knows about it and b) has given
       you explicit permission to use it!

       watchdog will send out three ping packages and wait up to <interval> seconds for the reply
       with  <interval> being the time it goes to sleep between two times triggering the watchdog
       device. Thus a unreachable network will not cause a hard reset but a soft reboot.

       You can also test passively  for  an  unreachable  network  by  just  monitoring  a  given
       interface for traffic. If no traffic arrives the network is considered unreachable causing
       a soft reboot or action from the repair binary.

       watchdog can run an external command for user-defined tests. A return  code  not  equal  0
       means  an error occured and watchdog should react. If the external command is killed by an
       uncaught signal this is considered an error by watchdog too.  The command may take  longer
       than  the  time  slice  defined  for  the  kernel device without a problem. However, error
       messages are generated into the syslog facility. If you have enabled softboot on error the
       machine  will  be  rebooted  if  the  binary doesn't exit in half the time watchdog sleeps
       between two tries triggering the kernel device.

       If you specify a repair binary it will be started instead of shutting down the system.  If
       this binary is not able to fix the problem watchdog will still cause a reboot afterwards.

       If  the  machine  is  halted  an email is sent to notify a human that the machine is going
       down. Starting with version 4.4 watchdog will also notify  the  human  in  charge  if  the
       machine is rebooted.

SOFT REBOOT

       A  soft  reboot (i.e. controlled shutdown and reboot) is initiated for every error that is
       found. Since there might be no more processes available, watchdog does it all by  himself.
       That means:

       1.  Kill all processes with SIGTERM.

       2.  After a short pause kill all remaining processes with SIGKILL.

       3.  Record a shutdown entry in wtmp.

       4.  Save  the random seed from /dev/urandom.  If the device is non-existant or there is no
           filename for saving this step is skipped.

       5.  Turn off accounting.

       6.  Turn off quota and swap.

       7.  Unmount all partitions except the root partition.

       8.  Remount the root partition read-only.

       9.  Shut down all network interfaces.

       10. Finally reboot.

CHECK BINARY

       If the return code of the check binary is not zero  watchdog  will  assume  an  error  and
       reboot  the  system.  Be  careful  with  this if you are using the real-time properties of
       watchdog since watchdog will wait for the return of  this  binary  before  proceeding.  An
       positive  exit  code  is  interpreted  as  an system error code (see errno.h for details).
       Negative values are special to watchdog:

       -1     Reboot the system. This is not exactly an error message but a command to  watchdog.
              If the return code is -1 watchdog will not try to run a shutdown script instead.

       -2     Reset  the  system. This is not exactly an error message but a command to watchdog.
              If the return code is -2 watchdog will simply refuse to  write  the  kernel  device
              again.

       -3     Maximum load average exceeded.

       -4     The temperature inside is too high.

       -5     /proc/loadavg contains no (or not enough) data.

       -6     The given file was not changed in the given interval.

       -7     /proc/meminfo contains invalid data.

       -8     Child process was killed by a signal.

       -9     Child process did not return in time.

       -10    Free for personal use.

REPAIR BINARY

       The  repair binary is started with one parameter: the error number that caused watchdog to
       initiate the boot process. After trying to repair the system the binary should exit with 0
       if  the  system  was  successfully  repaired  and thus there is no need to boot anymore. A
       return value not equal 0 tells watchdog to reboot. The return code of  the  repair  binary
       should  be  the error number of the error causing watchdog to reboot. Be careful with this
       if you are using the real-time properties since watchdog will wait for the return of  this
       binary before proceeding.

TEST DIRECTORY

       Executables  placed  in  the  test directory are discovered by watchdog on startup and are
       automatically executed.  They are bounded  time-wise  by  the  test-timeout  directive  in
       watchdog.conf.

       These  executables are called with either "test" as the first argument (if a test is being
       performed) or "repair" as the first argument (if a repair for a  previously-failed  "test"
       operation on is being performed).

       The  as  with test binaries and repair binaries, expected exit codes for a successful test
       or repair operation is always zero.

       If an executable's test operation fails, the same executable is automatically called  with
       the "repair" argument as well as the return code of the previously-failed test operation.

       For example, if the following execution returns 42:

           /etc/watchdog.d/my-test test

       The watchdog daemon will attempt to repair the problem by calling:

           /etc/watchdog.d/my-test repair 42

       This  enables  administrators  and  application developers to make intelligent test/repair
       commands.  If the "repair" operation is not required (or is not likely to succeed), it  is
       important that the author of the command return a non-zero value so the machine will still
       reboot as expected.

       Note that the watchdog daemon may interpret and act upon any of the reserved return  codes
       noted in the Check Binary section prior to calling a given command in "repair" mode.

BUGS

       None known so far.

AUTHORS

       The original code is an example written by Alan Cox <alan@lxorguk.ukuu.org.uk>, the author
       of the kernel driver. All additions were written by  Michael  Meskes  <meskes@debian.org>.
       Johnie  Ingram  <johnie@netgod.net> had the idea of testing the load average. He also took
       over the Debian  specific  work.  Dave  Cinege  <dcinege@psychosis.com>  brought  up  some
       hardware watchdog issues and helped testing this stuff.

FILES

       /dev/watchdog
              The watchdog device.

       /var/run/watchdog.pid
              The pid file of the running watchdog.

SEE ALSO

       watchdog.conf(5)