Monitoring Disk Usage with Bash Commands

Monitoring disk usage is essential for maintaining system health and ensuring adequate storage space. Here’s how you can monitor disk usage using various Bash commands:

1. Check Disk Space Usage

Command: df
Usage:
- View disk usage for all mounted filesystems:
```
df -h
```
- -h: Displays output in human-readable format (e.g., GB, MB).
- Filter for a specific filesystem or directory:
```
df -h /path/to/directory
```

2. Analyze Directory Sizes

Command: du
Usage:
- Display the size of a directory and its subdirectories:
```
du -h /path/to/directory
```
- Show only the total size of a directory:
```
du -sh /path/to/directory
```
- -s: Summarize the total size.
- -h: Human-readable format.

3. Monitor Disk Space in Real-Time

Command: watch
Usage:
- Use watch to run df repeatedly at intervals:
```
watch -n 5 df -h
```
- -n 5: Refresh every 5 seconds.

4. Find Large Files

Command: find

Usage:

Search for files larger than 1 GB:

find /path/to/search -type f -size +1G

List large files in human-readable format:

find /path/to/search -type f -size +1G -exec ls -lh {} \;

5. Monitor Inode Usage

Command: df (with the -i option)
Usage:
- Check inode usage to ensure you’re not running out:
```
df -i
```

6. Automate Monitoring with a Script

Example Bash Script:

#!/bin/bash

# Define thresholds
THRESHOLD=80
ALERT_EMAIL="admin@example.com"

# Monitor disk space
df -h | awk 'NR>1 {if ($5+0 > '"$THRESHOLD"') print $0}' > /tmp/disk_alert.txt

# Send email alert if thresholds are exceeded
if [ -s /tmp/disk_alert.txt ]; then
mail -s "Disk Space Alert" "$ALERT_EMAIL" < /tmp/disk_alert.txt
fi

7. System-Wide Disk Monitoring Tools

Consider using tools like ncdu or iotop for more advanced monitoring:

ncdu: A fast, interactive disk usage analyzer.

sudo apt install ncdu  # For Debian-based systems
sudo dnf install ncdu  # For Fedora/RHEL-based systems
sudo zypper install ncdu  # For openSUSE
ncdu /path/to/analyze

iotop: Monitor real-time disk I/O usage.

sudo apt install iotop  # For Debian-based systems
sudo dnf install iotop  # For Fedora/RHEL-based systems
sudo zypper install iotop  # For openSUSE
iotop

These commands and tools provide both basic and advanced methods for monitoring disk usage, helping you maintain system performance and prevent storage issues.