Kernel numbering and Fedora

| categories: fedora

By now it's made the news that the kernel version has jumped to version 5.0. Once again, this numbering jump means nothing except Linus decide that he wanted to change it. We've been through versioning jumps before (2.6 -> 3.x, 3.x -> 4.x) so practically we know how to deal with this by now. It still takes a bit of hacking on the kernel packaging side though.

Fedora works off of a package git (pkg-git) model. This means that the primary trees are not git trees of the actual source code but git trees of a spec file, patches, and any other scripts. The sources get uploaded in compressed archive format. For a stable fedora release (F28/F29 as of this writing), the sources are a base tarball (linux-4.19.tar.xz) and a stable patch on top of that (patch-4.19.14.xz). Rawhide is built off of Linus' master branch. Using 4.20 as an example, start with the last base release (linux-4.19.tar.xz), apply an -rc patch on top (patch-4.20-rc6.xz) and then another patch containing the diff from the rc to master on that day (patch-4.20-rc6-git2.xz). We have scripts to take care of grabbing from kernel.org and generating snapshots automatically so kernel maintainers don't usually think too much about this.

When there's a major version bump, most of our scripts break. This isn't just a matter of doing s/4/5/. Because the major version bump happens randomly, we can't easily script "if minor version == XXX pickup y as base". This means our existing code doesn't know how to pick up linux-4.20.tar.xz as a base and apply patch-5.0-rc1.xz on top of that. Because we've dealt with this before, other people have come up with the easiest solution which is a combination of hardcoding and using the full -rc tarball. This means that our base is linux-5.0-rc1.tar.xz and we generate snapshots on top of that (patch-5.0-rc1-git3.xz).

The kernel.spec and associated scripts look a bit hacked up at the moment. This is only for the next 6 weeks though, after which we will go back to our usual methods. All credit for this scheme goes to the maintainers before me.