Question 85513 in Docker Question posted in
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Run Docker on Raspberry Pi4 with overlay fs

I prefer to create a situation where on a Raspberry Pi4 Docker is running while the SD-card is read only. This with overlay fs.

In the dockercontainer a database is running, the data of the database is written to an USB-stick (volume mapping).

When overlayfs is activated (after reboot, enabled via “sudo raspi-config”), docker will not start-up any more.

The steps on https://docs.docker.com/storage/storagedriver/overlayfs-driver/
System information:
Linux raspberrypi 5.10.63-v8+ #1488 SMP PREEMPT Thu Nov 18 16:16:16 GMT 2021 aarch64 GNU/Linux

Docker information:

pi@raspberrypi:~ $ docker info
Client:
Context:    default
Debug Mode: false
Plugins:
  app: Docker App (Docker Inc., v0.9.1-beta3)
  buildx: Build with BuildKit (Docker Inc., v0.6.3-docker)
Server:
Containers: 1
  Running: 1
  Paused: 0
  Stopped: 0
Images: 1
Server Version: 20.10.11
Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Native Overlay Diff: true
  userxattr: false
………

Status docker after restart:

pi@raspberrypi:~ $ sudo systemctl status docker.*
Warning: The unit file, source configuration file or drop-ins of docker.service changed on disk. Run 'systemctl daemon-reload' to reload units.
● docker.socket - Docker Socket for the API
     Loaded: loaded (/lib/systemd/system/docker.socket; enabled; vendor preset: enabled)
     Active: failed (Result: service-start-limit-hit) since Thu 2021-12-09 14:30:43 GMT; 1h 13min ago
   Triggers: ● docker.service
     Listen: /run/docker.sock (Stream)
        CPU: 2ms
Dec 09 14:30:36 raspberrypi systemd[1]: Starting Docker Socket for the API.
Dec 09 14:30:36 raspberrypi systemd[1]: Listening on Docker Socket for the API.
Dec 09 14:30:43 raspberrypi systemd[1]: docker.socket: Failed with result 'service-start-limit-hit'
● docker.service - Docker Application Container Engine
     Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Thu 2021-12-09 14:30:43 GMT; 1h 13min ago
TriggeredBy: ● docker.socket
       Docs: https://docs.docker.com
   Main PID: 992 (code=exited, status=1/FAILURE)
        CPU: 162ms
Dec 09 14:30:43 raspberrypi systemd[1]: docker.service: Scheduled restart job, restart counter is at 3.
Dec 09 14:30:43 raspberrypi systemd[1]: Stopped Docker Application Container Engine.
Dec 09 14:30:43 raspberrypi systemd[1]: docker.service: Start request repeated too quickly.
Dec 09 14:30:43 raspberrypi systemd[1]: docker.service: Failed with result 'exit-code'.
Dec 09 14:30:43 raspberrypi systemd[1]: Failed to start Docker Application Container Engine.

Running the command given in docker.service with additional overlay flag

pi@raspberrypi:~ $ sudo /usr/bin/dockerd --storage-driver=overlay  -H fd:// --containerd=/run/containerd/containerd.sock
unable to configure the Docker daemon with file /etc/docker/daemon.json: the following directives are specified both as a flag and in the configuration file: storage-driver: (from flag: overlay, from file: overlay2)
pi@raspberrypi:~ $ sudo /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock
INFO[2021-12-09T14:34:31.667296985Z] Starting up
failed to load listeners: no sockets found via socket activation: make sure the service was started by systemd

Which steps am I missing to be able to run Docker with overlay fs, such that the SD-card in the Raspberry is read only?

Without the overlay fs active it all works as expected.

Tags:

2

Answers


  1. 0

    I ran into this issue as well and found a way around it. In summary, you can’t run the default Docker FS driver (overlay2) on overlayfs. Fortunately, Docker supports other storage drivers, including fuse-overlayfs. Switching to this driver resolves the issue but there’s one final catch. When Docker starts, it attempts to rename /var/lib/docker/runtimes and since overlayfs doesn’t support renames of directories already in lower layers, it fails. If you simply rm -rf this directory while Docker is stopped and before you enable RPi’s overlayfs, everything should work.

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  2. 0

    Referring to this answer Docker can’t create overlay on top of another overlay. That’s why your can’t overlay directory /var/lib/docker/(which Docker uses for storing it’s state, images and containers).

    You need to exclude /var/lib/docker from overlay: mount this directory to RAM with RW rights:

    sudo mount -t tmpfs tmpfs /var/lib/docker/

    Don’t forget to edit /etc/fstab to save your mount after reboot.

    Be aware that all your Docker images and containers will be cleared after reboot.

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