What are some essential Linux commands and their intriguing uses?

[heman]

i have some queries..i was trying to find out some commands in the manual..
like,,

--what command can be used for compressing files in Linux..

--how to check man page for /etc/passwd ?

--and i am not clear with this uid command?
why is the "set uid bit" set for "su" command?

--and in killing processes,why does killall -e doesn't work??

And please tell about interesting and hard to figure commands which you are familiar with..

 

[ComputerGeek]

1) gzip or bzip make sure to tar a group of files first.
2) man passwd
3)set uid bit means that one must authenticate as what ever user is designated in order to open what ever it is... it is set for su because that is the switch user command and you don't want some one running around being able to get into everyone elses account.. now do you? :-)

4) do you want to kill bash and all the services as well?