Hi all,

I have a process that I run regularly on my host PC. I download the stock Debian beaglebone image, mount the image as loopback devices, chroot into it, and make some changes.

I would like to do this same thing in a docker container via a gitlab pipeline. That is, when I tag a new version of our software, the pipeline builds it and then makes a new image with the new version installed.

I can't figure out how to get this to work. It seems like the container needs elevated permissions and/or access to the host's loopback device nodes, and I can't really find good resources for how this can work in gitlab. Beyond that, though, all I'm doing is manipulating the contents of a file I own, so it seems strange that there's no way to do that without elevated privileges.

As it is, what I'm trying (and failing) to do, looks something like this:

So, I make a loopback device (because one doesn't exist), then try to use losetup to hook it up to that image. Gitlab says the pipeline fails because "losetup: /tmp/dev/loop0: failed to set up loop device: Operation not permitted"

So, in googling that, I found a lot of people doing similar things, but no real solutions (and a lot of very old, obsolete posts). This got me thinking about why I need any elevated privileges at all, because really all I want to do is dump some files into the image.

I don't know much about fuse, but is that a potential answer? Or is there something else I'm missing that would work well here? And if I just need to force docker to let me do these thing, how would that work in gitlab?

Thanks

Docker runs as root and typically docker containers will run as the root user as well.
I was able to run those commands in a docker container with a root user without that error. Interestingly, it showed up outside my docker container, which probably goes to show why you should be careful running software in a docker container under a root user (which is common).
However, a pipeline will probably not be running the container as a root user. It's probably using a unprivileged user, which would explain why you're getting a operation not permitted error.