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Seth Woolley's Man Viewer Manual for watchdog - man watchdog. If programs in 1 , 8 user space are not longer executed it will hard reset 1 , 7 , 1 tput the system. Each write 1 , 2 delays the reboot time 1 , 2 , n another minute.
After a minute the watchdog 5 , 8 hardware will cause the reset. In the case of the software watchdog 5 , 8 the ability to reboot will depend on the state of the machines and interrupts. Check whether the process table is full. Check whether there is enough free memory available. Check whether some given files are accessible.
Check whether some given files change in 1 , 8 a given interval. Check whether the average work load 7 , n exceeds a predefined maximal value. Check whether the a file 1 , n table overflow occurred. Check whether a given process specified by a pid file 1 , n is still run- ning. Check whether some given IP addresses answer to a ping message.
Check whether some given network interfaces received some traffic. Check the temperature if 3 , n available. Execute a user defined binary to do arbitrary tests. If any of these checks fail watchdog 5 , 8 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. This is useful if 3 , n you want to see exactly what happened until watchdog 5 , 8 rebooted the system.
Currently it logs the temperature if 3 , n available , the load 7 , n average, the change date of the files it checks and how often it went to sleep. Be aware that the system is rebooted if 3 , n for any reason syncing lasts longer than a minute.
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 resp. Note that temperature checking is also disabled since this triggers the hardware watchdog 5 , 8 on some cards. Between each two tests it will trigger the kernel device. After finishing all tests watchdog 5 , 8 goes to sleep 1 , 3 for some time. The kernel drivers expects a write 1 , 2 to the watchdog 5 , 8 device every minute. Otherwise the system will be rebooted.
As a default watchdog 5 , 8 will sleep 1 , 3 for only 10 seconds so it triggers the device early enough. Under high system load 7 , n watchdog 5 , 8 might be swapped out of memory and may fail to make it back in 1 , 8 in 1 , 8 time.
Under these circumstances the Linux kernel will hard reset 1 , 7 , 1 tput the machine. To make sure you won't get unnecas- sary reboots make sure you have the variable 'realtime' set 7 , n , 1 builtins to yes in 1 , 8 the config 1 , 5 file 1 , n watchdog. It adds real time 1 , 2 , n support to watchdog. Thus it will lock itself into memeory and there should be no problem even under the highest of loads.
Also you can specify a maximal allowed load 7 , n average. Once this load 7 , n average is reached the system is rebooted. You may specify maximal load 7 , n averages for 1 minute, 5 minutes or 15 minutes. The default values is to disable this test. Be careful not to set 7 , n , 1 builtins this parameter too low. To set 7 , n , 1 builtins a value less 1 , 3 then the predefined minimal value of 2, you have to use the -f option.
You can also specify a minimal amount of virtual 5 , 8 memory you want to have available as free. As soon as more virtual 5 , 8 memory is used action is taken by watchdog. Note, however, that watchdog 5 , 8 does not distinguish between different types of memory usage. It just checks for free vir - tual 5 , 8 memory. If you have a watchdog 5 , 8 card with temperature sensor you can specify the maximal allowed temperature. Once this temperature is reached the sys - tem is halted.
Default value is There is no unit conversion. So make sure you use the same unit as your hardware. When using file 1 , n mode watchdog 5 , 8 will try stat 1 , 2 the given files. Errors returned by stat 1 , 2 will not cause a reboot. For a reboot the stat 1 , 2 call has to last at least one minute. This may happen if 3 , n the file 1 , n is located on an NFS mounted filesystem.
If your system relies on an NFS mounted filesystem you might try this option. However, in 1 , 8 such a case the sync 1 , 2 , 8 option may not work if 3 , n the NFS server is not answering. If you give watchdog 5 , 8 a pidfile it will read 2 , n , 1 builtins the pid from this file 1 , n and call kill 1 , 2 , 1 builtins pid ,0 to 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 5 , 8 wakes up again and cathes it. In ping mode watchdog 5 , 8 tries to ping the given addresses. These addresses do not have to be a single machine. It is possible to ping to a broadcast address instead to see if 3 , n at least one machine in 1 , 8 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! Thus a unreachable network will not cause a hard reset 1 , 7 , 1 tput but a soft reboot. You can also test passively for an unreavhable network by just monitor- ing a given interface for traffic. If no traffic arrives the network is considered unreachable causing a soft reboot resp.
With using an external check binary watchdog 5 , 8 can run user defined tests. This may last longer than the time 1 , 2 , n slice defined for the kernel device without a problem. However, note that in 1 , 8 this case error 8 , n mes- sages are generated into the syslog 2 , 3 , 5 , 3 Sys:: If you have enabled soft- boot on error 8 , n the machine will be rebooted if 3 , n the binary doesn't exit 3 , n , 1 builtins in 1 , 8 half the time 1 , 2 , n watchdog 5 , 8 sleeps between two tries triggering the ker- nel 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 5 , 8 will still cause a reboot afterwards. If eventually the machine is halted an email is send 2 , n to notify a human that the machine is going down.
Starting with version 1 , 3 , 5 4. Since there might be no more processes available, watchdog 5 , 8 does it all by himself. If the device is non-exis- tant or the filename to save to is empty this step is skipped. Be careful with this if 3 , n you are using the real-time properties of watchdog 5 , 8 since watchdog 5 , 8 will wait for the return of this binary before proceeding.
An positive exit 3 , n , 1 builtins code is interpreted as an system error 8 , n code see errno. Negative values are special to watchdog: This is not exactly an error 8 , n message but a com - mand to watchdog. If the return code is -1 watchdog 5 , 8 will not try to run a shutdown 2 , 8 script instead.
This is not exactly an error 8 , n message but a command to watchdog. If the return code is -2 watchdog 5 , 8 will simply refuse to write 1 , 2 the kernel device again. After trying to repair the system the binary should exit 3 , n , 1 builtins with 0 if 3 , n the system was successfully repaired and thus there is no need to boot anymore. A return value not equal 0 tells watchdog 5 , 8 to reboot. The return code of the repair binary should be the error 8 , n number of the error 8 , n causing watchdog 5 , 8 to reboot.
Be careful with this if 3 , n you are using the real-time properties of watchdog 5 , 8 since watchdog 5 , 8 will wait for the return of this binary before proceed- ing. BUGS None known so far. He also took over the Debian specific work.
References for this manual incoming links.