The 2023 Linux Launchpad: Part 4 - The Mechanic

The Why

A server is a living engine. Processes stall, memory leaks, and disks fill up. You must be the mechanic who can pop the hood and diagnose the engine while it's running 5,000 RPM.

The Commands

1. top / htop

The Dashboard. Shows CPU usage, Memory, and running processes in real-time.

zain@linux:~$ top
# Press 'q' to exit

2. df -h (Disk Free)

How much space do I have left? The -h flag makes it "human-readable" (GB instead of bytes).

zain@linux:~$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1        50G   25G   25G  50% /

3. free -m

Show me the RAM. Displays used and free memory in Megabytes.

zain@linux:~$ free -m

4. ps aux

List every single running process on the system.

zain@linux:~$ ps aux | grep firefox

5. kill

Terminate a frozen or rogue process using its PID (Process ID).

zain@linux:~$ kill 1234
# Forcing it to die:
zain@linux:~$ kill -9 1234

Try It Yourself

1. run top and identify the process using the most CPU.
2. Check your disk space: df -h.
3. Check your memory usage: free -m.
4. Find the PID of your shell: ps aux | grep bash.