As a first step to solving this, I tried to get the Docker Volume Plugin working on my Mac. I had to go down the rabbit hole somewhat to do so, and I'm sharing what I found here in case it helps point the way for you on the Raspberry Pi and, frankly, because it took me several hours to figure all this out and I need to post it somewhere!
The rclone Docker Volume Plugin doc instructs you to create a pair of directories on the host:
% sudo mkdir -p /var/lib/docker-plugins/rclone/config
% sudo mkdir -p /var/lib/docker-plugins/rclone/cache
I did so, and tried to install the plugin, but:
% docker plugin install rclone/docker-volume-rclone args="-v" --alias rclone --grant-all-permissions
latest: Pulling from rclone/docker-volume-rclone
Digest: sha256:fd1396468c3b3613081a1b10a2b4173219f9b3d43b2aedceab6830c84d821094
c3ef44c55cda: Complete
Error response from daemon: failed to create shim task: OCI runtime create failed: runc create failed: unable to start container process: error during container init: error mounting "/var/lib/docker-plugins/rclone/config" to rootfs at "/data/config": stat /var/lib/docker-plugins/rclone/config: no such file or directory: unknown
The problem is that the Mac is not the Docker host. The Docker host is a Linux instance running in a VM. This Linux instance has its own filesystem that overlaps with the Mac filesystem in some places, but not in others. In particular, /var on the Mac is not the same as /var on the Docker host.
If you don't see this error, then Docker on the Raspberry Pi likely uses the Pi's Linux OS as the host, but read on, there's more...
When Docker installs the plugin, it tries to mount the host's /var/lib/docker-plugins/rclone/config directory as /data/config in the plugin, and fails, since that directory does not exist on the host. There is a workaround, though. On the Mac, /var is a soft link to /private/var, and the Mac's /private directory is accessible from the host, and therefore the plugin.
Following advice here, I uninstalled and reinstalled the plugin, configuring it to use the /private directories for its config and cache:
% docker plugin install rclone/docker-volume-rclone:arm64 \
--alias rclone --grant-all-permissions \
args="-v --allow-other" \
config="/private/var/lib/docker-plugins/rclone/config" \
cache="/private/var/lib/docker-plugins/rclone/cache"
This allowed the plugin to install cleanly; the next step was to create a volume, using the exact same command that you used:
% docker volume create test -d rclone -o type=b2 -o b2-account=${B2_APPLICATION_KEY_ID} -o b2-key=${B2_APPLICATION_KEY}
Error response from daemon: create test: VolumeDriver.Create: failed to save state: open /data/cache/docker-plugin.state: operation not permitted
Now the issue is that, even though the host has made the config and cache directories available to the plugin, the plugin can't write to them, since the Linux host runs as the current user rather than as root.
If you didn't see this error, then the plugin is able to write its state file, so the following fix won't apply to you.
It turned out that the fix was easy - change the owner of the plugin's directories to the current user:
sudo chown $(whoami):staff /var/lib/docker-plugins/rclone/config
sudo chown $(whoami):staff /var/lib/docker-plugins/rclone/cache
After removing the test volume, I was able to use the same command as in your post to create a volume and then access it without any problems:
% docker volume create test -d rclone -o type=b2 -o b2-account=${B2_APPLICATION_KEY_ID} -o b2-key=${B2_APPLICATION_KEY}
test
% docker run --rm -it -v test:/mnt --workdir /mnt ubuntu:latest bash
root@eee9adc6b4ad:/mnt# ls
...all the buckets in my B2 account...
root@eee9adc6b4ad:/mnt# cat metadaddy-public/hello.txt
Hello from US West
root@eee9adc6b4ad:/mnt# echo 'Hello from docker' > metadaddy-public/docker.txt
Check it out: https://f004.backblazeb2.com/file/metadaddy-public/docker.txt
So, we know that your docker volume create command works just fine, and the problem must lie elsewhere.
One more diagnostic: from the Mac command line, I can see the plugin's state file, and read its contents:
% ls -l /var/lib/docker-plugins/rclone/cache
total 8
-rw------- 1 ppatterson staff 279 Apr 28 14:20 docker-plugin.state
% cat /var/lib/docker-plugins/rclone/cache/docker-plugin.state | jq .
[
{
"name": "test",
"mountpoint": "/mnt/test",
"created": "2023-04-28T21:20:28.892544708Z",
"fs": "",
"type": "b2",
"options": {
"b2-account": "*****",
"b2-key": "*****"
},
"mounts": [
"f8a9355b3ec90a13a6244583c4ae735b794c0741dfa72a9230680c7fe134ea36"
]
}
]
Now that I have it working on my Mac, I'll pull out a Raspberry Pi and try it there.
What version of RPi are you using, and what OS/Docker versions are you running on it?