rootfs persistence

[hansbogert]

what directories need to be made a (docker) volume, in order to make the configuration persistent?

[Rast1234]

Here's ideas i explored:

• Mounting OverlayFS inside container, like OpenWrt does, is not a good idea because it requires escalating privileges for Docker.
• Committing container as new image is possible but requires scripting around start/stop process and only could happen on container shutdown.
• There is not much information about which folders in OpenWrt are crucial for backing up. So if you just persist /etc and /bin, something will break sooner or later.
• Let's persist everything then! I copied all files from image to host and tried to mount that as /. Docker does not allow this unfortunately.
• This is due to runtime-created directories like /run and /proc. My current workaround is that i mount everything copied from image as a separate volume.
• Original OpenWrt container kinda loses its purpose after this, so i just use empty one with predefined CMD and ENV.

My Dockerfile and docker-compose:

FROM scratch
CMD /sbin/init
ENV PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

version: "3.9"
services:
  openwrt:
    container_name: openwrt
    # image built from above Dockerfile
    image: openwrt:empty
    # my network setup... replace with yours
    cap_add: [NET_ADMIN] 
    network_mode: none
    # mounting every folder from original container
    volumes:
      - /mnt/stuff/docker/openwrt/bin:/bin
      - /mnt/stuff/docker/openwrt/etc:/etc
      - /mnt/stuff/docker/openwrt/lib:/lib
      - /mnt/stuff/docker/openwrt/lib64:/lib64
      - /mnt/stuff/docker/openwrt/mnt:/mnt
      - /mnt/stuff/docker/openwrt/overlay:/overlay
      - /mnt/stuff/docker/openwrt/rom:/rom
      - /mnt/stuff/docker/openwrt/root:/root
      - /mnt/stuff/docker/openwrt/sbin:/sbin
      - /mnt/stuff/docker/openwrt/tmp:/tmp
      - /mnt/stuff/docker/openwrt/usr:/usr
      - /mnt/stuff/docker/openwrt/var:/var
      - /mnt/stuff/docker/openwrt/www:/www