investigation

How to Recover Disk Space on a Full Linux Server

If your Linux server runs out of disk space, here’s a quick, effective process to find and fix the problem.

1. Check Disk Usage

Start by seeing which filesystem is full:

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df -h

If you suspect inode exhaustion (lots of tiny files), check:

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df -i

2. Find Large Directories

Identify which folders use the most space:

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sudo du -h -d 1 -x / 2>/dev/null | sort -hr | head -20
  • -x keeps the scan on the main filesystem.
  • For an interactive view, try ncdu:
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sudo apt install ncdu
sudo ncdu -x /

3. Remove Unneeded Large Files

Look for unusually large files, especially in /usr/local, /var, or /home. Static libraries (.a files) and old build artifacts are common culprits. If you find something you no longer need, remove it:

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sudo rm /path/to/large/file
sudo ldconfig

4. Fix “Phantom” Disk Usage

If df shows more used space than du, you may have deleted files still held open by running processes. Find them with:

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sudo lsof +L1 2>/dev/null | awk 'NR==1 || $7+0 > 10000000'

Restart the process holding the file (e.g., Docker):

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sudo systemctl restart docker

5. Prevent Future Issues (Docker Log Rotation)

Docker logs can silently fill your disk. Set up log rotation in /etc/docker/daemon.json:

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{
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "50m",
    "max-file": "3"
  }
}

Restart Docker:

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sudo systemctl restart docker

Recreate containers to apply the new policy.

Quick Cleanup Commands

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docker system df
docker container prune -f
docker builder prune -af
docker image prune -af
journalctl --disk-usage
sudo journalctl --vacuum-size=200M
sudo apt autoremove --purge
sudo apt clean

This version removes personal anecdotes and focuses on actionable steps, making it easy to follow as a general-purpose tutorial.

Total recovered: ~7GB. Total time: about 20 minutes. Lesson value: priceless.