Useful Linux Commands

In this article I will show you the commands that I use the most on my Ubuntu vps.

Navigation

Command	Action
ls -alth	show content of folder
wc -l <path to file>	display the number of lines in a file
pushd <path>	go to a directory and save the path in history
popd	rollback to previous directory from pushd
dirs -v	show pushd history
cd -	get back to previous directory (reset history)
mkdir -p /folder/folder2	create a new directory with non existing folders
find . -name "*.yaml"	find all files that end by ".yaml" in current directory

File editing

Command	Action
pwd > test.txt	send the content of a command to a file (erase the previous content)
pwd >> test.txt	add the content of a command to the next line of a file
pwd | tee test.txt	same as pwd > test.txt but print it in cli
pwd | tee -a test.txt	same as pwd >> test.txt but print it in cli
grep "ubuntu" test.txt | wc -l	connect commands (for instance to get number of line with a word)

System

Command	Action
ps aux	list all processes for all users
ps aux | grep	Find a running process by name
top and htop	List current running process by cpu usage
free -m	get memory usage
df -h	get volumes % still available, always check that biggest volume is not > 90%
sudo du -sh * | sort -h	sort biggest folders
sudo du -ahx / | sort -rh	head -n 20
sudo ss -tulpn | cat | grep :8080 => kill -15	find if a port is already used by a process, then kill it
dig google.com	check if a domain name is valid
curl -v <url>	execute an http request
ip a	see private and public ip adress

systemctl

Command	Action
sudo systemctl start my-api.service	start systemctl
journalctl -u my-api.service -f	show logs of a systemctl service in real time
journalctl -u my-api.service -p err	show only errors for a systemctl service
sudo journalctl --vacuum-time=2d	remove logs older than 2 days