Follow the below links for some useful Linux commands (with examples).
Please note that this is intended to merely be a quick reference. If you need complete and thorough documentation, see the links in the reference section.
awk - manipulate text
dhclient - manage DHCP
chmod - change permissions on files or directories.
chown - change file or directory owner.
cp - copy files or folders
crontab - configure scheduled tasks
dig - Domain Name System Information Groper (lookup DNS information)
find - Find files
grep - GNU Regular Expression Parser (find strings of text in files)
git - Software repository and version control
ip - manage IP addresses and such (replaces ifconfig... more or less)
mtr - (use instead of traceroute)
netstat - provides information about the network connection and activity
rsync - file copying utility (remote sync)
screen - manages multiple virtual terminal screens on one physical screen
sed- parse and edit text
SSH - Securely connect to a remote computer.
tar - Create and manage tar archive files.
vim - Command line text editor.
xargs - build a command from standard input
zcat - view zipped files without un-zipping them