* whoami : displays current user
* top : displays the top cpu/memory eaters and system load.. like task manager on windows
* ps : displays all processes running.. ps aux is the most useful way to run it
* wall “some text” : sends a broadcast message to all logged on users
* man program : displays the ‘man page’ or manual for a given program. Use space bar to page down and q to exit
* program -h : displays the help for a given program, briefer than man
* du -sh dirName : Displays the total size of a directory recursively
* df -kh : displays total and available storage on all partitions for the system
* locate filename : finds ware a program or file is located on the system
* w : displays who is ssh’ed or logged in.
* watch -n seconds filename : will execute a file every n seconds. Useful to watch who is online, watch -n 3 w
* wget http://somesite.com/somefile : gets a file via ftp, rsync, http, etc from a remote host.
* netstat : displays all listening ports and active connections
* ifconfig : used for listing network interface info and setting it
* clear : clears the terminal
* md5sum filename : displays the md5 checksum of the given file