How to move images of docker in aufs directory to overlay2?

Question

I update my kernel of Debian from 3.x to 4.x.
Docker storage become overlay2.

ls /var/lib/docker/ 
containers  image  network  overlay2  plugins  swarm  tmp  trust  volumes

old directory structure is

aufs  containers  graph  image  init  linkgraph.db  network  plugins  repositories-aufs  swarm  tmp  tmp-old  trust  volumes

My images is in aufs directory, I can not start docker service with old directory. how can I move my images to overlay2?

Answer 1

1. Identify the images to save and restore after migrating from aufs to overlayfs2.

2. Export all the images to be migrated to overlayfs into one archive - this is faster and efficient

   sudo docker save $IMAGES -o /data/save.tar

   Here IMAGES is a variable containing the image names

3. Create /etc/docker/daemon.json with following contents:

   {
     "storage-driver": "overlay2"
   }
   

   [ Refer to https://stackoverflow.com/questions/42245288/add-new-element-to-existing-json-array-with-jq/57537190#57537190 for updating it using jq ]

4. Take the backup of the directory where docker images are stored and delete the directory

   mv /var/lib/docker/images /var/lib/docker.aufs.images

5. systemctl daemon-reload

6. systemctl restart docker

7. docker load < save.tar