lsof -i:port
1.1 Kill process is listening on any port
kill $(lsof -t -i:port)
xdg-open [file/folder name]
2.1 open current folder
xdg-open .
ufw
3.1 list status firewall
sudo ufw status
3.2 open any port
sudo ufw allow 25
3.3 block an ip address
sudo ufw deny from 155.232.212.143
4.1 Check os infor
cat /etc/*release*
4.2 check ram infor
free -h
lsof -i :8000