About SIGKILL

[cyrus]

Is SIGKILL in UNIX operating system a forceful kill.Where can one find the reason when a SIGKILL occurs.

[sammy]

Two signal which can neither be ignored nor catched by invoking a signal handler are SIGKILL and SIGSTOP. It is necessary for the super user to have the powers to kill any process with SIGKILL or stop it with SIGSTOP. This is one of the main scenarios in which SIGKILL takes its presence.

[Sandhya.Kishannag]

SIGKILL causes it to terminate immediately this signal cannot be caught or ignored, and the receiving process cannot perform any clean-up upon receiving this signal.

SIGKILL gives the process no opportunity to do cleanup operations on terminating, in most system shutdown procedures an attempt is first made to terminate processes using SIGTERM, before resorting to SIGKILL if the process does not voluntarily exit in response to SIGTERM.
To speed the computer shutdown procedure, Mac OS X 10.6, aka Snow Leopard, will send SIGKILL to applications that have marked themselves "clean" resulting in faster shutdown times with, presumably, no ill effects.
An uninterruptibly sleeping process may not terminate even when sent SIGKILL. This is one of the few cases in which a UNIX system may have to be rebooted to solve a temporary software problem.