LPI Linux Certification in a Nutshell, 2nd Edition

Objective 5: Create, Monitor, and Kill Processes

This Objective looks at the management of processes. Just as file management is a fundamental system administrator's function, the management and control of processes is also essential for smooth system operation. In most cases, processes will live, execute, and die without intervention from the user because they are automatically managed by the kernel. However, there are times that a process will die for some unknown reason and need to be restarted. Or, some process may "run wild" and consume system resources, requiring that it be terminated. You will also need to instruct running processes to perform operations, such as rereading a configuration file.

Processes

Every program, whether it's a command, application, or script, that runs on your system is a process. Your shell is a process, and every command you execute from the shell starts one or more processes of its own (referred to as child processes). Attributes and concepts associated with these processes include:

Lifetime

A process lifetime is defined by the length of time it takes to execute (it's "life"). Commands with a short lifetime such as ls will execute for a very short time, generate results, and terminate when complete. User programs such as web browsers have a longer lifetime, running for unlimited periods of time until terminated manually. Long lifetime processes include server daemons that run continuously from system boot to shutdown. When a process terminates, ...