Installing docker in custom folder with daemon.json not working

I'm trying to install Docker to a custom folder rather at the default location of /var/lib/docker. The official Docker documentation says you can specify the default location by specifying data-root in the daemon.json file located /etc/docker/daemon.json. More info can be found here.

In the OMV web-GUI the Docker storage field says "Leave blank to use custom /etc/docker/daemon.json." which I have done but Docker never seems to be able to install and start. Below is the contents of the daemon.json file:

{
  "data-root": "/srv/dev-disk-by-label-DATA1/AppData/Docker"
}

However, specifying the new Docker installation path in the field as detailed in the guide here allows Docker to be installed and start up.

Any idea what's going on here?

Leaving the box blank didn't work on the version of OMV I was running at the time of writing the post hence why I had to specify the full path manually. The good news is that it seems to working now, now that I've done a clean install of OMV to the latest version. The only change with the configuration is shared folder paths now use UUID's.

Below are the steps I have taken to change the default path for Docker:

1) I created a directory 'docker' at '/etc'

2) I created a file daemon.json at '/etc/docker' and set permissions to that I could write to the file over a SFTP client

3) I used a SFTP client on Windows to edit the file and entered the following:

{  "data-root": "/srv/dev-disk-by-uuid-dceac721-a86b-4d95-9866-c79109fbe9ca/AppData/Docker"}

4) I went to the web-GUI > OMV Extras > Docker, cleared the 'Docker Storage' field and clicked the 'Save' button.

5) After the settings had been applied I clicked install

6) Docker is successfully installed and running