How do I mount/browse the files of a deployment on the composefs backend?

[renner0e]

For testing/troubleshooting of a (staged) deployment on the ostree backend you can just go into /sysroot/ostree/boot.X/fedora/XXX/ and then browse the filesystem of that deployment.

How is this supposed to be done on the composefs backend? This would be useful for querying a package database of a deployment to show changelogs between them for example. In the spirit of what rpm-ostree db diff does. As far as I can tell, there is currently no documentation regarding this.

Although I noticed when I mount /sysroot/composefs/images/XXX /mnt there is a skeleton of a filesystem but all the files are "empty", so that is definitely the wrong approach to do that.

[jeckersb]

In general you shouldn't need to worry about the details of the specific backend implementations. For comparing the package databases between two deployments I would do a $(rpm -qa | sort) with podman (or your container tool of choice) on the containers associated with the deployments and then compare them.

If you really really want to mount it, you can do so with cfsctl mount.

[renner0e]

Thanks for the quick answer, my intention was for this to be run on a client without networking and using the disk as sparingly as possible. I have thought about doing it via podman run and this would work but pulling images is something I wanted to avoid. I know that bootc invokes podman --root... to operate on the bootc owned storage but I couldn't make this work for myself.

I guess I'd want bootc image cmd run ... but sadly that does not exist to my knowledge.

[Smujb]

The command you're looking for is bootc internals cfs mount [verity] [mountpoint]. I found this while looking for cfsctl.

Here's a proof of concept I made for diffing the package db using Python (currently only supports pacman & composefs backend): https://github.com/Smujb/bootc-tools/blob/main/bootc-db-diff