No blog would be complete without a Linux cheat sheet. I compiled this list when I first started learning Linux, and I’ve had it in my private wiki for a while. This list is mainly just a brain-dump, is not comprehensive, and is mostly targeted at Debian or derivatives.
If you want a good list of quick diagnostic commands, check out First 5 Minutes Troubleshooting A Server.
Get Help for Most Any Command
$ man ls
This would display the help file for the command "ls".
Execute Something as SuperUser
This assumes you are in the sudoers file. You will be prompted for your password.
$ sudo <command>
To become super user permanently for your shell session, use sudo -s. Note this is dangerous and you shouldn’t do it most of the time!
Get the Current Version of Linux
$ uname -a
Linux toboe 2.6.13-15-default #1 Tue Sep 13 14:56:15 UTC 2005 i686 i686 i386 GNU/Linux
Print the Contents of a Text File
The first command here (cat) dumps the whole file, while the second command (less) lets you page through the file.
$ cat /etc/cronttab
$ less /var/log/kern.log
Analyze Disk Usage
$ df -h
/dev/hda3 14G 2.2G 12G 17% /
tmpfs 252M 12K 252M 1% /dev/shm
/dev/hda2 87M 39M 49M 45% /boot
Find a Running Process
$ ps -ae | grep ssh
1435 ? 00:00:00 sshd
1877 ? 00:00:00 sshd
1879 ? 00:00:00 sshd
Find Devices Available (e.g. CDROM’s, HD’s, etc)
This command uses the wildcard character * to find all devices starting with ‘sd’. sd is the prefix typically given to hard disks. You could replace ‘sd’ with ‘cd’ to find cdrom drives, etc.
$ ls /dev/sd*
/dev/sda /dev/sda1 /dev/sda2 /dev/sda5
Mount a CD/DVD ROM Drive
$ mount /dev/cdrom /media/cdrom
List all Loaded Modules
Module Size Used by
ext2 52937 1
loop 11799 0
i2c_i801 7830 0
snd_hda_codec_analog 64562 1
radeon 574812 0
Install a Package
For this example, we will install tcpdump. Note we are using sudo to run as super-user.
$ sudo apt-get update
$ sudo apt-get install tcpdump
To send a running process to the background you can press CTRL-Z.
To restore it to the foreground, use ‘fq’.
+ Stopped sudo tcpdump -i eth0