1. uname

uname -a

Displays kernel and system information.

2. df

df -h

Shows disk space usage of filesystems.

3. free

free -h

Displays memory and swap usage.

4. uptime

uptime

Shows how long the system has been running.

5. dmesg

dmesg | less

Displays kernel ring buffer messages.

6. journalctl

journalctl -xe

Views systemd logs with detailed info.

7. top

top

Real-time system resource monitoring.

8. htop

htop

Interactive process viewer (better than top).

9. lscpu

lscpu

Displays CPU architecture information.

10. lsblk

lsblk

Lists information about block devices.

11. hostnamectl

hostnamectl

Displays or changes the system hostname.

12. systemctl

systemctl status

Controls systemd services and shows status.

13. ps

ps aux

Shows running processes.

14. vmstat

vmstat 1

Reports virtual memory statistics.

15. iostat

iostat

Displays CPU and I/O statistics.

16. tune2fs

sudo tune2fs -l /dev/sda1

Shows/ext. filesystem parameters and stats.