Cheat Sheet Linux¶

CLI Commands and shortcuts¶

Command	Description	Example	Explanation
`!!`	Repeat last command	`$ apt-get install curl` `Permission Denied` `$ sudo !!`	No retyping required
`!$`	Reuse last argument	`$ mkdir logs` $ cd !$	!$ becomes logs
`^old^new`	Replace typo in last command	`$ cat fil.txt` `$ ^fil^file`	No retying required
`Alt + .`	Cycle last arguments	`$ cat config.yaml` `cat <Alt+.>`	inserts server_config.yml
`xargs`	Turns outputs into arguments	`$ ls *.log \| xargs rm`	xargs takes all the .log files and gives them to rm for deletion
`tee`	Save outout whilst viewing it	`$ male build \| tee output.log`	Watch the output on screen whilst saving to a log
`grep -R "lookup"`	Search inside files	`$ grep -R "error" .`	Scans all files in current DIR recursively for "error"
`fc`	Edit and re-run last command	`$ fc`	Opens the last command in Vim so you can more easily edit it
`!!:n`	Get a specific argument from last command	`$ echo dog cat monkey` `$ echo !!:2` `$ cat`	2 represents the argument placement
`Ctrl + a`	Move around CLI	`Ctrl + a`	Moves cursor to the start of the line
`Ctrl + e`	Move around CLI	`Ctrl + e`	Moves cursor to the end of the line
`CTRL + w`	Quick delete	`CTRL + w`	Deletes word before the cursor
`CTRL + u`	Quick delete	`CTRL + u`	Deletes everything after the cursor
`!!:gs/old/new`	Replaces text	`$ echo dog dog` `$!!:gs dog/cat` `$ cat cat`	Find keyword and replace
`df -h`	Check disk usage	`$ df -h`	Disk free space in human readable format
`df -sh *`	Check disk usage	`$ df -sh *`	Files and folder sizes in current DIR
`lsof -i :<port>`	What's using the port	`$ lsof -i :80`	What's running HTTP on the server
`nc -zv <host> <port>`	Is this port accessible	`$ nc -zv grinntec.net 443`	Can i reach Grinntec on HTTPS

Alias¶

Open the bash config file

sudo nano ~/.bashrc

Add your alias to the end of the file, for example:

alias ll="ls -lh"
alias cd..="cd .."

Restart your shell

List running services¶

systemctl list-units --type=service --state=running

Create command alias¶

Edit the shell config file

nano ~/.bashrc

Add the alias to the end of the file. This example allows you to use just ls to get a full ls -la output.

alias ls='ls la'

Restart the shell

source ~/.bashrc

Rename a directory¶

To rename a directory in Linux, you can use the mv command with the current directory name and the new directory name.

mv [current directory name] [new directory name]

Display all users¶

To display all the users who exist on the server and sort them by name, you can use the "cat" command to read the "/etc/passwd" file and then pipe the output to the "cut" and "sort" commands.

cat /etc/passwd | cut -d: -f1 | sort

List file including hidden¶

ls -la ~

Check status of Apache¶

systemctl status apache2

Show the OS release¶

lsb_release -a

apt-get error: repository suite error¶

error when using apt-get update; the suite has changed to oldstable and needs to be accepted before you can use it

Reading package lists... Done
E: Repository 'http://archive.raspberrypi.org/debian buster InRelease' changed its 'Suite' value from 'testing' to 'oldstable'
N: This must be accepted explicitly before updates for this repository can be applied. See apt-secure(8) manpage for details.
E: Repository 'http://raspbian.raspberrypi.org/raspbian buster InRelease' changed its 'Suite' value from 'stable' to 'oldstable'
N: This must be accepted explicitly before updates for this repository can be applied. See apt-secure(8) manpage for details.

To accept the change to the suite value run the following command

sudo apt-get update --allow-releaseinfo-change