This content has been automatically translated from Ukrainian.
You deploy the application on Coolify, the build passes successfully… and suddenly at the image export stage:
ERROR: failed to extract layer sha256:... write /var/lib/containerd/.../File/dirname-c.ri: no space left on device
The build has completed, but there is nowhere to write the image - the disk is full.
🤔 Why this happens
Docker accumulates junk with each deployment:
- Old images - each build creates a new image, old ones remain
- Build cache - intermediate layers of the build are never automatically deleted
- Stopped containers - undeleted containers from previous deployments
- Unused volumes - remnants from deleted services
On a small server (4–8 GB disk), this can fill up the disk within a few weeks of active development.
Especially if you are running Rails + Sidekiq + Redis + Elasticsearch.
🔎 Diagnosis
Check the disk status:
df -h
See how much space Docker is using:
docker system df
Usually, you will see tens of gigabytes in the Images or Build Cache section.
🛠 Fix
docker system prune -a --volumes
This command removes:
- All stopped containers
- All networks that are not in use
- All images without active containers
- All build cache
- All volumes without active containers (--volumes)
⚠️ Attention
--volumes will also delete data in volumes.
If your database (PostgreSQL / MySQL) is running through a Docker volume without an external backup - first make a dump.
🧼 Prevention
To avoid getting into this situation regularly:
Add a cron for automatic cleanup
Every week at 3:00 AM (without volumes, to avoid affecting the DB):
0 3 * * 0 docker system prune -af
Increase the disk
If you are running:
- Rails
- Elasticsearch
- Redis
- Sidekiq
4 GB disk is not enough.Comfortable minimum: 20-40 GB.
Limit build cache
docker builder prune --keep-storage 2GB
This allows you to keep the cache but prevents it from growing uncontrollably.
If the deployment fails with no space left on device - this is not a bug in the application.Docker has simply accumulated too much old data.
One command:
docker system prune -a --volumes
solves the problem in seconds.
But it's better to set up automatic cleanup so you don't have to think about it during the next release
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