Docker exec/attach not working on overlayed root


Beek, Léon van de
 

Hi Bruce,

 

To be honest, I am not quite sure where to ask this, as it is a very specific scenario, so feel free to forward me and my question to someone/somewhere else.

 

Situation:

  • Yocto Hardknott running meta-virtualization, meta-raspberrypi with Docker installed: Dockers works fine and is tested. Docker exec and attach works too
  • Now changed the rootfs to be squashfs, and an overlay of root + a RW ext4 partition is changed to be / at boot. This script is based on: https://github.com/cmhe/meta-readonly-rootfs-overlay
  • Docker’s overlay2 file driver does not work on top of an overlay: https://docs.docker.com/storage/storagedriver/select-storage-driver/
  • Solution: create /etc/docker/daemon.json with the line in it: “data-root”=”/docker-data”. Note: /docker-data is a separate EXT4 partition on the SD card.
  • Restart machine/dockerd. The result is that we see the /docker-data is now full of docker files and the containers and overlay2 folders are there. Docker info shows: Storage driver: overlay2
    Containers run fine. Hello-world example runs. Alpine runs, and when starting Alpine with -it arguments I can mess around in shell all I want, everything works.
  • Problem: Whenever I create a container, for example: docker run -d -t –name=test alpine, and later try to exec into it using “docker exec test echo hello” I get this result:
    Error running exec: OCI-runtime exec failed: exec failed: container_linux.go:367”starting container process caused: read init-p: connection reset by peer: unknown
  • I restarted dockerd with –log-level=debug and noticed that it says: attach: stderr: begin, stream copy error: reading from a closed fifo. (Same for stdout)

 

I removed the overlaying again and can confirm that exec and attach also worked before adding this, but on Google I can not find a single thing that closely relates to the issue I am facing.

 

Hope any of you might be able to help me out here, I feel truly stuck on this.

 

Kind regards,

Léon van de Beek

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