cp
copy a file
mv
move a file
rm
remove a file or directory
chmod
change mode(accessibility) of a file system object
chown
change file owner and group
apt-get
Install, update, or remove
yum
Install, delete, update
ip
manage the network interfaces
df
disk free, view file systems and free space
grep
find text in a file
ps
view the current processes
top
view CPU, RAM, and resource utilizations
dig
lookup info from DNS servers
nano
text editor