docker system prune: Reclaim Disk in CI

Reclaim disk by removing everything unused - the CI cleanup hammer.

docker system prune removes unused Docker data: stopped containers, dangling images, unused networks, and build cache. This page covers the aggressive flags safe for CI.

What it does

By default docker system prune removes stopped containers, networks not used by a container, dangling images, and dangling build cache. -a also removes all unused (not just dangling) images; --volumes adds unused volumes.

Common usage

Terminal

docker system prune -f
docker system prune -af                 # also unused images
docker system prune -af --volumes       # also unused volumes (CI hammer)

Common errors in CI

This is the standard fix for "no space left on device" on a runner: docker system prune -af --volumes between jobs. Without -f it prompts "Are you sure?" and hangs in non-interactive CI - always pass -f. Beware --volumes deletes data volumes you might still need; on shared runners scope cleanup to the current job rather than wiping everything.

Related guides

Docker "no space left on device" - Causes and FixesWhy Docker builds fail with "no space left on device" in CI, and how to reclaim space, prune layers, and stop… docker system df: See Where Docker Disk GoesHow docker system df works: showing disk used by images, containers, volumes, and build cache, with -v for pe… docker image prune: Remove Unused ImagesHow docker image prune works: removing dangling or all unused images, the -a flag, age filters, and reclaimin… docker volume prune: Remove Unused VolumesHow docker volume prune works: bulk-removing unused volumes, the -a flag, and reclaiming volume disk on CI ru…