Let me give some usefull linux commands and utilities. Please add to this list if you know.

Work with tar files.
To make tar archive use

$ tar -cvf filename.tar filename

To extract tar archive use
$ tar -xvf filename.tar

To extract tar archive with gz use

$ tar -xzvf filename.tar.gz

Connect to remote system through ssh

$ ssh name@ip followed by passwd
e.g. ssh project@172.16.0.14 passwd:

List the file in current directory
$ ls -l
list the running process
$ps -e

Start or Stop or Restart Network
/etc/init.d/networking start (In ubuntu)
/etc/init.d/networking restart (In ubuntu)
/etc/init.d/networking stop (In ubuntu)
/etc/init.d/network start ( In Fedora)
/etc/init.d/network restart ( In Fedora)
/etc/init.d/network stop ( In Fedora)