Key Commands (Practice these!): ◦ls (list files/folders), ls -l (detailed list) ◦cd (change directory), pwd (print working directory) ◦cat (display file contents), less (page-by-page viewing) ◦grep (search for text in files) ◦top (real-time process/resource usage) ◦ps aux (show all running processes) ◦df -h (disk free space, human-readable) ◦du -sh (disk usage for folder) ◦ping (network connectivity) ◦ip addr show/ip a (show IP addresses) ◦sudo (run as administrator) ◦reboot (restart server) ◦ssh user@server_ip (remote login) ◦hostnamectl set-hostname (change hostname) ◦netstat -tuln/ss -tuln/lsof -i (check open ports) ◦systemctl status/start/stop/enable (manage services) ◦journalctl (view systemd logs) ◦adduser, deluser, passwd (manage users) ◦crontab -e (schedule jobs) ◦smartctl (check hard drive health) ◦lshw, lspci, lsblk, lsusb, dmidecode (list hardware)