Finding What Is Filling the Disk

Every build leaves layers and every run leaves a container, and neither is cleaned up for you. On a machine that builds often this becomes tens of gigabytes without anything appearing to be wrong.

bash

$ docker system df
TYPE            TOTAL     ACTIVE    SIZE      RECLAIMABLE
Images          48        3         14.2GB    12.8GB (90%)
Containers      21        2         1.1GB     1.0GB (95%)
Local Volumes   9         1         3.4GB     3.1GB (91%)
Build Cache     312       0         21.7GB    21.7GB (100%)

RECLAIMABLE is the number that matters: what is not being used by anything running. The build cache is usually the largest and the least missed, since losing it costs one slow build.

bash

$ docker system prune
$ docker system prune --volumes   # only if you are sure

Docker
Containers