Managing Disk Space on Your Server

Check Overall Disk Usage

df -h

Shows each partition, total size, used space, available space, and mount point. Watch for any partition above 80% usage.

Find Large Directories

du -sh /* 2>/dev/null | sort -rh | head -20

Interactive Disk Usage Browser — ncdu

apt install ncdu -y
ncdu /

Navigate with arrow keys, press d to delete a file or directory, q to quit.

Common Disk Space Culprits

Old log files:

ls -lh /var/log/
journalctl --disk-usage
journalctl --vacuum-size=500M   # Keep only 500 MB of system logs

APT package cache:

apt autoremove -y
apt clean

Docker unused images/containers:

docker system prune -a

Old Linux kernels (Ubuntu):

apt autoremove --purge -y

Monitor Disk Usage Over Time

watch -n 5 df -h

Set Up a Low-Disk Alert

Add this to your crontab to email you when disk usage exceeds 85%:

0 6 * * * df -h | awk '$5+0 > 85 {print}' | mail -s "Disk Alert" you@example.com