There are a number of good resources on the web. Here's one of them:

http://linuxcommand.org/index.php

Note: this does not apply to users who log in with their Unity Id and password.

passwd

There is a 12-character minimum length requirement on the cluster.

pwd - print working directory
ls - list files
cd - change directory
less - file pager
file - describes type of a file

cp - copy 
mv - move (rename)
rm - remove (delete)
mkdir - make directory
rmdir - remove directory

Choose an editor:

nano
vi
emacs

#!/bin/bash
...

Make a script file “executable”:

chmod u+x scriptname

man COMMAND
man ls

Save output from a command to file.

ls > file.txt

This lets you run multiple terminals that are immune to “hang-ups” (network errors) and can remain active even after you log out. You “detach” from the terminal and then re-attach after logging back in.

screen

Other terminal multiplexers (byobu, tmux) are also installed on the cluster.

Find a file by name:

find . -name lost_file.txt

find is a very flexible (and quite complicated) tool for finding files and applying commands to the results. It's well worth learning more about this command.

Calculate the total size of a directory:

du -sh dirname