Package overlayroot and docker

Question

Has anyone gotten overlayroot and docker to work together? I'm running Ubuntu 18.04.3LTS and docker daemon won't start up.

Specifically:

sudo apt-get install docker.io overlayroot

sudo docker ps #works, no errors.

Edit /etc/overlayroot.conf to change: overlayroot="" to overlayroot="tmpfs"

sudo update-initramfs -u

sudo reboot #to reboot into the read only overlay filesystem

sudo docker ps # Get the following error:

Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

ps: to remove the overlay filesystem do the following:

sudo overlayroot-chroot

Edit that same file to put it back to the original.

sudo update-initramfs -u

exit #to exit the chroot environment

sudo reboot #your system is back to a normal read/write Ubuntu system and "sudo docker ps" works again.

Answer 1

Solved my own problem.

Docker uses an overlay2 file system in /var/lib/docker. An overlay2 filesystem cannot be used on an overlay file system that overlayroot uses. It can however reside on it as regular files. So my solution was to: make a copy of /var/lib/docker/overlay2. Mount a tmpfs on /var/lib/docker/overlay2 On boot - copy that copy of /var/lib/docker/overlay2 to that tmpfs. Start up docker. Docker now sees it on an tmpfs, not an overlay file system.