Lockfiles for packages in a Debian/Ubuntu rootfs
github.com
github.com
I wrote apt2ostree. It applies the cargo/npm lockfile idea to debian rootfs images. From a list of packages we perform dependency resolution and generate a "lockfile" that contains the complete list of all packages, their versions and their SHAs. You can commit this lockfile to git.
You can then install Debian or Ubuntu into a chroot just based on this lockfile and end up with a functionally reproducible result. It won't be completely byte identical as your SSH keys, machine-id, etc. will be different between installations, but you'll always end up with the same packages and package versions installed for a given lockfile.
This has saved us on a few occasions where an apt upgrade had broken the workflow of some of our customers. We could see exactly which package versions changed in git history and roll-back the problematic package before working on fixing it properly. This is vastly better than the traditional `RUN apt-get install -y blah blah` you see in `Dockerfile`s. You know exactly what was installed before an update and exactly what is installed after and you can rebuild old versions.
IMO it's also more convenient than debootstrap as you don't need to worry about gpg keys, etc. when building the image. Dependency resolution and gpg key stuff is done at lockfile generation time, so the installation process can be much simpler. In theory it could be made such that only dpkg is required to do the install, rather than the whole of apt, but that's by-the-by.
apt2ostree itself is probably not interesting to most people as it depends on ostree and ninja but I think the lockfile concept as applied to debian repos could be of much broader interest. The lockfile generation could be easily separated from apt2ostree. Most of it is implemented in a custom fork of aptly anyway. Actually applying the lockfiles and creating a rootfs from it is much more apt2ostree specific and would probably need to be reimplemented separately to be more generally useful. Ideally that would be built in to dpkg, but I don't think I'm the man to drive that consensus.