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1. Linux Help Commands

apropos        apropos keyword – 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.
man        man -k keyword – Show all commands with the keyword in their description
“man 2 kill” – Display page 2 of the kill command
manpath        Determine user’s searchpath for manpages.
info        Documentation on Linux commands and programs similar to the man pages but navigation is organized different.

2. Linux Job Management

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.
cron        A deamon used to set commands to be run at specific times. Starts the commands in the crontab file. Used to clean up temporary files periodically in the /var/tmp and /tmp directories.
nice        Run a program with modified scheduling priority.
nohup        Run a command immune to hangups, with output to a non-tty.
watch       Execute a program periodically showing output full screen.

3. Linux Process management

bg        Starts a suspended process in the background
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.
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)

Meanings:

* PPID-parent process ID
* PID-process ID

ps ax |more to see all processes including daemons
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.
CTRL-C        Kills the current job.
&         At the end of the command makes it run in the background.