Some useful UNIX command

Daily work require me to work faster and familiar with the OS.
UNIX OS is one of them.

Here some unix command help my daily life:
ls - list file
chmod - change file permission
umask - set default file/directory creation permission
rm - remove
rmdir - remove directory
touch filename - create new file
mkdir - create new directory

References:
UNIX Tutorial for Beginners http://www.ee.surrey.ac.uk/Teaching/Unix/