Linux goodness again

Some more commands to know

Command	Description
gzip/gunzip	Zip a file using GNU Zip and unzip it e.g. gzip filename
tar	Create an archive of files e.g. tar cvf output.tar inputfile1 inputfile2 where c creates the new archive, v gives verbose output and f tells tar it is dealing with a file. To extract (x) files from an archive use tar xvf output.tar
free	Displays the memory usage on a system
halt	Shutdown linux
shutdown	Shutdown linux
reboot	Restarts the computer
kill	Force a process to shutdown e.g. kill -9 PID where PID is the process ID which can be obtained from using the top command
top	Shows the most important processes
uname	Display information about the system e.g. uname -a
ps	Display the current running processes e.g. ps ax –cols 132 will show all the processes formatted into the terminal
pstree	Shows the parent-child relationships for the running processes
groups	Prints the groups that include a specified user e.g. groups root
id	Print the user and group ID for a given user e.g. id root
passwd	Change the user password
su	Switch user. If there is no argument then it switches to root
df	Displays disk usage and space available e.g. df -h
du	Disk usage statistics e.g. du -ah /etc for all files in human readable format kept in /etc
cal	Show a calendar e.g. cal 2013
date	Show the current time and date