Kill

From Sysadmin

The Unix kill command will send a signal to a process. The default signal is sigterm but many other signals can be sent.

SIGTERM

This is the default signal for kill. All processes sent the signal are requested to close. They may ignore this signal.

SIGSTOP

This signal will set a stop flag on each process receiving the signal. The process will remain in memory but will not be scheduled to run on the CPU until the stop flag is removed. In top the stop flag is represented by a T in the list of flags.

SIGKILL

This will cause each process receiving the signal to be shutdown by the kernel. The process will not be given an opportunity to save any data. Many new Unix users, on learning of kill -9, start using it routinely. It is strongly advised to only use SIGKILL if SIGTERM is not closing the processes or if it is known with certainty that it will not close the processes.