Unfortunately you can’t currently reclaim the space like that:
$ df -h
Filesystem Size Used Avail Capacity iused ifree %iused Mounted on
/dev/disk1 112Gi 111Gi 330Mi 100% 29237368 84358 100% /
...
Then:
$ docker rm $(docker ps -aq)
...
$ docker rmi $(docker images -q)
...
And still:
$ df -h
Filesystem Size Used Avail Capacity iused ifree %iused Mounted on
/dev/disk1 112Gi 111Gi 329Mi 100% 29237470 84256 100% /
...
And the problem is the sparse file:
$ ls -lh ~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/Docker.qcow2
-rw-r--r-- 1 amouat staff 9.3G 25 Apr 15:15 /Users/amouat/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/Docker.qcow2
The only fix I know of is to delete the file and start again, which obviously wipes out all your images and containers