No Space Left on Device: How to Free Disk Space on Linux

The short answer: what to do

No space left on device means one of two things: you ran out of bytes or you ran out of inodes (file entries). Work step by step:

1. Find out which partition is full: df -h.
2. Check inodes: df -i.
3. Find what takes the space: du or ncdu.
4. Clean safely: logs, Docker, caches.
5. Set up rotation so it does not happen again.

Do not delete random files in /var or /usr — find out what they are first.

Step 1. Which partition is full

df -h

Look at Use% and Mounted on. Often it is not the whole disk but a single partition: /, /var or /boot.

Step 2. Find the culprit

The heaviest directories on the root partition:

sudo du -xh --max-depth=1 / | sort -rh | head -20

The -x flag keeps it on one filesystem. Then go deeper: /var, /var/log, /home, /opt.

It is easier interactively with ncdu:

sudo apt install ncdu   # or dnf install ncdu
sudo ncdu -x /

You can browse directories with arrow keys and see sizes immediately.

Large individual files:

sudo find / -xdev -type f -size +500M -exec ls -lh {} \;

Step 3. Usual suspects and how to clean them

Logs. The systemd journal can grow large:

journalctl --disk-usage
sudo journalctl --vacuum-size=500M

Application logs in /var/log or the project directory: if a file is being written right now, do not rm it — empty it instead: sudo truncate -s 0 /var/log/app.log.

Docker. Old images, stopped containers, unused volumes and build cache:

docker system df
docker system prune
docker image prune -a

The --volumes flag also removes unused volumes — they may hold database data. Use it only when you know exactly what is there. Container logs grow too: limit them in the logging driver settings (max-size, max-file).

Package caches:

sudo apt clean          # Debian/Ubuntu
sudo dnf clean all      # RHEL/Fedora

Also check npm, pip and CI build caches in home directories, old backups and database dumps.

Deleted a file but the space did not come back

If you delete a file a process still holds open, the space is freed only when the file is closed. Find such files:

sudo lsof +L1

Restart the process holding them and the space returns.

Running out of inodes

df -h shows free space but files cannot be created — check df -i. If IUse% is near 100%, the cause is a huge number of tiny files: sessions, cache, temp files, queued mail.

Find the directory with the most files:

sudo du --inodes -x / 2>/dev/null | sort -rn | head -20

Delete what is not needed and fix the cause, for example by cleaning old sessions automatically.

Step 4. Set up log rotation

logrotate archives and deletes old logs on a schedule. An example for an app — the file /etc/logrotate.d/myapp:

/var/www/myapp/logs/*.log {
    daily
    rotate 14
    compress
    missingok
    notifempty
    copytruncate
}

Dry run without applying: sudo logrotate -d /etc/logrotate.d/myapp. For journald, set SystemMaxUse in /etc/systemd/journald.conf.

Most importantly, set up disk usage monitoring that alerts you in advance, not after the service has already crashed.