I'm not sure if this is an OMV issue, a Docker issue, a docker config issue, an image issue, or a local filesystem rights issue. It seems like some of my Docker containers that run their processes as a user other than root, have problems with DNS. For example, my Nextcloud container has been unable to check for updates. The process runs as www-data. When I run "docker -it -u www-data nextcloud /bin/bash" and then run "curl http://www.google.com", it fails to resolve the url. If I connect to the container as "docker -it nextcloud /bin/bash" and run "curl http://www.google.com" it returns data as expected.
I checked the rights of /etc/resolve.conf and it was set to rw only for root and no other permissions (600). After setting the permissions to 644, suddenly everything worked.
So my question is...is this issue caused by the container, by docker, by the docker config, or by the underlying FS permissions?
I have docker using a shared folder instead of the default /var/lib/docker location. When I created the Nextcloud instance, I pointed it to the location I wanted and it created the folder for me so the rights on the "config" folder should be correct. Although the config folder is mounted to /var/www/html within the container anyways.
I have docker running on an Ubuntu VM (completely separate from OMV), and I've never once run into this issue on it. Granted it's also using the default /var/lib/docker. When I've run into this issue on my OMV system, I would even test it on my Ubuntu system and wouldn't have the problem there.