Unix Commands Cheat Sheet

Unix Cheat Sheet

Below is a cheat sheet of Unix commands that are useful for Linux server administration. This is by no means an exhaustive list, however it is very useful for beginners. These commands were used on my server running Debian 6.0.

ls – list the contents of the directory you’re in

ls -a – list the contents of the directory you’re in (including hidden files)

ls -l – shows you file permissions and ownership

cd – change directory

cp – copy

scp – secure copy

chmod – change permissions

chown – change the owner of a file

/ – top level directory

Tab key – autocomplete words

pwd – tells you what directory you are in

echo – echo argument

grep – search file

wc – count characters/words/lines

up arrow – shows your previous commands

mkdir (directory name) – make a new directory with the name given

rm -R (directory name) – delete directory

cd ../ – move up a directory in the file system (parent directory)

touch (filename) – create file

nano (filename) – create file using nano command line text editor

cat – view the contents of a text file.

more – view the contents of a text file, allows you to view by page (spacebar to move to the next page)

rm (filename) – delete file

rm *.(filetype) – delete all files of a specified type

rmdir – remove directory

apt-get update – updates the package cache

apt-get upgrade – upgrading packages

apt-get dist-upgrade – upgrades the kernel etc.

apt-get install (package name e.g. nano) – install package

&& – join commands together

^ – symbol is Ctrl (called the caret)

Ctrl + C – cancels the command

wget (filename/link to a filename on the internet) – downloads the file/package specified

logout – logout

reboot – reboot

sudo logout – logout (only needs sudo if a non root user)

sudo reboot – reboot server (only needs sudo if a non root user)

su – – logs in as root if already logged in as a non root user

rwxr-xr-x – file permissions shown as: read, write, execute. Shown for owner, group and user

Commands for Server Optimisation

top – displays real time CPU processes and resources being used by CPU-intensive tasks

apt-get update – Updates the cache on local machine so it is aware of what files the Linux repository has got, and where they are.

apt-get upgrade – Applies the changes/updates that are available in the update command.

free -m – Show you the RAM memory usage at any specific time. (-m shows it in megabytes)

uname -r – Shows the kernel version.

uname -a – Shows what kernel version is running, more about the operating system, whether 64-bit or 32-bit and what processor you are using.

cat /etc/lsb-release OR

cat /etc/issue OR

ls -l /etc/system-release – Find out what distribution your running and what version.

df -TH – Find out how much hard disk space is being used.

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