Free up disk space on an Ubuntu or Debian server

In a hurry? whyfull checks for this and every other common cause in one command.

When a server runs out of space, it's tempting to start deleting whatever looks big. Most of the space on an Ubuntu or Debian server is in a handful of predictable places, and each has a command that cleans it safely. Work through them in this order: the first steps are the safest and often free enough on their own.

1. See what's full

df -h
df -i

df -h shows space per filesystem. df -i shows inodes: if IUse% is at 100%, the problem is too many small files, not too many bytes, and the inodes guide covers that instead.

2. Find where the space is

sudo du -xh --max-depth=1 / | sort -h

-x keeps du on one filesystem, so it doesn't count other disks mounted under /. Run it again on the biggest directory (/var is the usual one) until you know what's using the space. If the total is much smaller than what df reports, read df says full but du doesn't add up before deleting anything.

3. Clear the apt cache

apt keeps every package it has downloaded in /var/cache/apt/archives. They're only needed to reinstall without downloading again.

sudo du -sh /var/cache/apt
sudo apt clean

Then remove packages that were installed as dependencies and are no longer needed:

sudo apt autoremove --purge

Read the list before you confirm. It usually includes old kernels, which is what you want, but check that nothing you still use is on it.

4. Remove old kernels

Each kernel takes a few hundred MB across /boot and /lib/modules. apt autoremove removes most of them. If old kernels are still installed, or /boot is a separate partition that's full, follow removing old kernels.

5. Shrink the systemd journal

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

To stop it growing back, set SystemMaxUse=500M in /etc/systemd/journald.conf and run sudo systemctl restart systemd-journald. The journal guide has the details.

6. Deal with large logs in /var/log

Old rotated logs (syslog.2.gz, auth.log.1) can be removed. A log that is still being written to should be truncated, not deleted, because deleting it doesn't free the space while the program has it open:

sudo truncate -s 0 /var/log/syslog

If one log keeps filling the disk, find out why the program is logging so much, and have logrotate rotate it by size. See /var/log is full.

7. Remove old snap revisions

snapd keeps old revisions of every snap. List the disabled ones:

snap list --all | awk '/disabled/ {print $1, $3}'

Remove each one by name and revision:

sudo snap remove firefox --revision=4793

To keep only two revisions from now on (the minimum):

sudo snap set system refresh.retain=2

8. Clean up Docker

On a server that runs containers, Docker is often the biggest thing on the disk.

docker system df
docker image prune -a
docker builder prune

docker image prune -a removes images that no container uses, and docker builder prune removes the build cache. Be careful with docker volume prune: volumes hold data, and unused isn't always the same as unwanted. Container logs without a size limit are another common cause. The Docker guide covers both.

9. Delete old core dumps

When a program crashes, apport (Ubuntu) and systemd-coredump can keep a dump of its memory, sometimes several GB each.

sudo du -sh /var/crash /var/lib/systemd/coredump
coredumpctl list

If you don't need them to debug the crash, remove them:

sudo rm -f /var/crash/*.crash
sudo rm -f /var/lib/systemd/coredump/*

10. Check caches in home directories

Build tools keep large caches in each user's home directory: pip, npm, Go, Cargo, Maven, Gradle, Hugging Face models. They're rebuilt when needed.

sudo du -sh /home/*/.cache /root/.cache 2>/dev/null | sort -h

Use each tool's own cleanup command where it has one, for example pip cache purge, npm cache clean --force or go clean -cache, run as the user who owns the cache.

If df still says full

If you've deleted files and df hasn't moved, a process still has them open. Find it with:

sudo lsof +L1

Restarting that process frees the space. Deleted files still using space explains how to free it without a restart.