Unzip:

• sudo apt-get install unzip
• unzip [file]

Tar:

• tar -cvvf foo.tar [directory]

Untar:

• tar -zxvf yourfile.tar
• tar -xvfz filename.tar.gz
• tar -xvzf filename.tar.gz [directory]
• tar -jxvf filename.tar.bz2

Find: find [dir] -type d|f -iname ‘searchstring’

• find / -type -d -iname ‘python’
• find ~ -type d -exec chmod +x {} \;

Delete a user account

• sudo deluser <username>

Add an New user

• sudo useradd <username>

or

• sudo useradd -d /home/<directory> -m <username>

( -d specifies home directory, -m makes the folder if it doesn’t exist )

useradd doesn’t add password unless you add -p     …. or you can just set the password later with:

• sudo passwd <username>

If called with two non-option arguments (see below), adduser will add an existing user to an existing group.

Make a new Group: 

• groupadd <groupname>

To see what groups currently exist:

• cat /etc/group

To see current users logged in:

• w

Count lines in file:

• wc -l <filename>