system/notes/docker.md

Backup and restore volumes

Backup a volume

docker run \
  --rm \
  --volumes-from source_container_name \
  -v $(pwd):/backup \
  busybox tar cvf /backup/backup.tar /path/to/volume

Restore volume from a backup

docker run \
  --rm \
  --volumes-from target_container_name \
  -v $(pwd):/backup \
  busybox sh -c "cd /path/to/volume && tar xvf /backup/backup.tar --strip 1"

Clean overlay2 folder

docker image ls --all --format "{{.ID}}" | xargs -n1 docker inspect | egrep '"Id"|/merged'

You'll see something like the following:

"Id": "sha256:f8fa7183309d043e93c78224f93e8bce028be5ac331b994e3f3654b8980e7d61",
    "MergedDir": "/var/lib/docker/overlay2/8eb1a12796c337c8a60f00d6721c26a0dd7ceba66f28f3a66be0cb5b08505561/merged",

And now it safe to remove merged dir

rm -rf /var/lib/docker/overlay2/8eb1a12796c337c8a60f00d6721c26a0dd7ceba66f28f3a66be0cb5b08505561