Linux Chapter 9

process priority

A number assigned to a process, used to determine how many time slices on the processor that process will receive; the higher the number, the lower the priority.

user process

A process begun by a user and which runs on a terminal.

foreground process

A process for which the BASH shell that executed it must wait for its termination.

background process

A process that does not require the BASH shell to wait for its termination. Upon execution, the user receives the BASH shell prompt immediately.

rogue process

A process that has become faulty in some way and continues to consume far more system resources than it should.

zombie process

A process that has finished executing but whose parent has not yet released its PID; the zombie still retains a spot in the kernel's process table.

parent process

A process that has started other processes (child processes).

child process

A process that was started by another process (parent process).

daemon process

A system process that is not associated with a terminal.

process ID (PID)

A unique identifier assigned to every process as it begins.

renice command

Used to alter the nice value of a process currently running on the system.

nice command

Used to change the priority of a process as it is started.

nohup command

Used to execute a child process without parent association.

top command

Used to give real-time information about the most active processes on the system; it can also be used to renice or kill processes.

pgrep command

Used to list the PIDs of processes that match a regular expression or other criteria.

ps command

Used to obtain information about processes currently running on the system.

atrm command

Used to remove a scheduled at job.

foreground (fg) command

Used to run a background process in the foreground.

background (bg) command

Used to run a foreground process in the background.

watch command

Used to run a process repeatedly at the specified second interval.

pkill command

Used to send a kill signal to processes that match a regular expression or other criteria.

kill command

Used to send kill signals to a process by PID.

atq command

Used to view a scheduled at job.

crontab command

Used to view and edit user cron tables.

at command

Used to view, create, and manage scheduled tasks that run at a preset time in the future.

process state

The current state of the process on the processor; most processes are in the sleeping or running state.

trap

The process of ignoring a kill signal.

kill signal

The signal sent to a process for use in terminating or restarting processes; different kill signals affect processes in different ways.

at daemon (atd)

The system daemon that executes tasks at a future time; it is configured with the at command.

cron daemon (crond)

The system daemon that executes tasks repetitively in the future and that is configured using cron tables.

nice value

The value that indirectly represents the priority of a process; the higher the value, the lower the priority.

cron table

A file specifying tasks to be run by the cron daemon; there are user cron tables and system cron tables.

jobs command

Displays background processes running in the current shell.

pstree command

Displays processes according to their lineage, starting from the init daemon.

lsof (list open files) command

Lists the files that are currently being viewed or modified by processes and users.

killall command

Sends kill signals to processes by process name.

parent process ID (PPID)

The PID of the parent process that created the current process.

forking

The act of creating a new BASH shell child process from a parent BASH shell process.

time slice

The amount of time a process is given on a CPU in a multiprocessing operating system.