System Monitoring and Resource Management Commands: | Notion

15) `free` – Memory usage

Function: Shows RAM and swap.
Syntax:
```
free -h
```
Lesson: Helps diagnose memory leaks.

16) `df` – Disk space

Function: Displays disk usage.
Syntax:
```
df -h
```
Lesson: Always check before downloads or installations.

17) `lsblk` – List block devices

Function: Shows disks and partitions.
Syntax:
```
lsblk
```
Lesson: Useful for attaching new storage volumes.

18) `du` – Directory space usage

Function: Shows how much space folders take.
Syntax:
```
du -sh *
```
Lesson: Helps identify large folders quickly.