at: Similar to cron but run only once.
atq: Lists the user's pending jobs. If the user is the superuser, everybody's jobs are listed.
atrm: Deletes at jobs.
atrun: Run jobs queued for later execution
batch: Executes commands when system load levels drop below 0.8 or value specified in atrun invocation.
bg: Starts a suspended process in the background
cron: A deamon used to set commands to be run at specific times.
CTRL-C: Kills the current job.
fg: Starts a suspended process in the foreground
gitps: A graphical process viewer and killer program.
jobs: Lists the jobs running
kill: Ex: "kill 34" - Effect: Kill or stop the process with the process ID number 34.
killall: Kill processes by name. Can check for and restart processes.
nice: Run a program with modified scheduling priority.
nohup: Run a command immune to hangups, with output to a non-tty.
pidof: Find the process ID of a running program
ps: Get the status of one or more processes. Options: u (more info), a (see all), -l (technical info)
pstree: Display the tree of running processes.
sa: Generates a summary of information about users' processes that are stored in the /var/log/pacct file.
skill: Report process status.
snice: Report process status.
top: Display the processes that are using the most CPU resources.
watch: Execute a program periodically showing output full screen.
&: At the end of the command makes it run in the background.
Unix and Linux System Management Commands
exit: Terminates the shell.
halt: Stop the system.
init: Process control initialization.
initscript: Script that executes inittab commands.
logout: Log the user off the system.
poweroff: Brings the system down.
reboot: Reboot the system.
runlevel: List the current and previous runlevel.
setsid: Run a program in a new session.
shutdown: System shutdown.
telinit: By requesting run level 1 a system can be taken to single user mode.
Unix and Linux Help Commands
apropos: Show all commands with the keyword in their description. The same as the "man -k" command.
help: Bash shell help for the bash builtin command list. The help command gets help for a particular command.
man: Get help from the manual for a command. Option –k keyword - Show all commands with the keyword in their description
manpath: Determine user's searchpath for manpages.
info: Documentation on Linux commands and programs similar to the man pages but navigation is organized different.