Here are important commands that you should be aware of:
- cat - input from stdin or a file and output to stdout or a file
- df - find out how much space is free on your disks
- du - find out how much space is used on your disks
- ethtool - is a network cable connected and which link does it have?
- fdisk - partition a hard disk
- file - find out the type of a file
- hwinfo - find out what harddisk, processor, graphics card and so on you have
- ls - list files
- scp - copy over the network
- ssh - call a program over the network on another computer
- which - where does a program lodge?