move /var/lib/docker to different volume for docker images

Problem 1 - need move /var/lib/docker to large volume

Our local linux disk volume is under 30GB, so it will be quite challenge for our docker images, which take a lot of space under /var/lib/docker folder and quickly run out of space.

Solution for Problem 1

It is possible to follow this artile - Use a Different Volume For Your Docker Images in Ubuntu that mount a new volume folder e.g. /dev/sda2 for /var/lib/docker and add the following line

/dev/sda2    /var/lib/docker    ext4    defaults    0    1

in /etc/fstab so the mount also happen during startup linux.

A quick tip to get volume type is using command df -T

What I did in fact follow this artile - How to move docker data directory to another loccation on Ubuntu

• stop the docker daemon

$ sudo service docker stop

and make sure that docker is not running

$ ps faux | grep -i docker

• make the folder and rsync the files

$ mkdir /mnt/docker
$ rsync -avxP /var/lib/docker/ /mnt/docker

• Update docker configuration
  • Add a configuration file and tell the docker daemon what is the location of the data directory by creating a file called daemon.json under directory /etc/docker. the file should have the content:

{
    "data-root":"/mnt/docker"
}

• Update the docker service by editing /lib/systemd/system/docker.service Find the following line

ExecStart=/usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock

and update to

ExecStart=/usr/bin/dockerd -g /mnt/docker -H fd:// --containerd=/run/containerd/containerd.sock

• Re-start the docker daemon

sudo service docker start
# reload docker serivce configuration 
sudo systemctl daemon-reload

• test by the following command after you pull an image

docker inspect image_id | grep WorkDir

Problem 2 - After linux reboot, docker images are gone

The docker images under /mnt/docker are gone, e.g. /mnt/docker/overlay2 has no docker images that we pulled fromm DockerHub.

See github discussion https://github.com/moby/moby/issues/36149
and PR https://github.com/moby/sys/pull/62

Solution for Problem 2

No solution yet, keep looking! So far, have to re-pull the docker images.