Friday, July 2, 2010

bash: fork: Resource temporarily unavailable

The error is generated because of recursive defunct processes going on in the memory and is unable to allocate specific amount of memory for the newly created process. Basically the general structure of process generation is as followed.

This is the normal life of a program.

The program is started by a parent process, an action called fork()
The fork makes a copy(the child) of the calling process(the parent).
exec() The child then issues an exec() system call which replaces the new
process with the intended executable file.

SRUN/URUN (system/user run space) the new child program now runs. Now the parent is either waiting(in a SLEEP) for the child to finish or checks for the childs completion or the system notifys the parent on exit
of the child process.

The child exits and returns the resources(memory) to the system.
ZOMBIE At this point the child has terminated and is in ZOMBIE. THIS IS NORMAL!! It will stay in this state until the parent process acknowledges receipt of the appropriate signal or terminates.

If the parent process has died unexpectedly or something else has prevented acknowledgment from the parent then process ID #1 (init) takes over and becomes the childs parent until reboot.

A zombie does not tie up memory but it still has a slot in the process table. I/O devices can get locked out.

You can't kill a ZOMBIE process because......IT'S ALREADY DEAD!!!

So finally try to check these defunct processes going on server You can do this by giving the ps -dfa command and killing manually. If this work you can start by simply relogin into the shell and if not you will need a reboot to the server in order to refresh the memory states.

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