I pruned all images, containers and the build cache, leaving only couple of small volumes. The system shows that everything is cleared:
% docker system df
TYPE TOTAL ACTIVE SIZE RECLAIMABLE
Images 0 0 0B 0B
Containers 0 0 0B 0B
Local Volumes 2 0 134.1MB 134.1MB (100%)
Build Cache 0 0 0B 0B
Still, the Docker Preferences pane shows that 12.5 GB of disk space are still occupied:
The space is taken by /Users/Vladimir.Ryabtsev/Library/Containers/com.docker.docker/Data/vms/0/data/Docker.raw. I don’t remember if it was like that right after the installation. Is is the space consumed by the Docker system itself? The name is a bit misleading then, as it makes me thing this space is occupied by images.