Today I couldn't get systemd 38-3 to boot and it hangs at a debug console that won't accept root password or boot after CTRL+D. I was able to downgrade to the previous system 37-4 with files I downloaded to a memstick, then with chroot I used "rpm -i --force ./systemd*" (not recommended but yum wouldn't let me downgrade without lots of dependencies other than systemd). I then erased the faulty systemd 38-3 and reinstalled local systemd 37-4 with yum.
My question is how do I get "yum history undo XX" or "yum history rollback XX" to work? yum always complains that the previous files are no longer available for downgrade. I also tried enabling other Fedora repos like updates-testing and then downgrading, but yum now complains that Rawhide files are only available for upgrade. Downloading files and their dependencies to a memstick is a pain, since rebooting and chroot is slow. I'm asking in Rawhide, since downgrading a nonbooting system comes up often for me.
Okay now systemd 39-1 does the same thing. Fails to log off, and won't boot. Now I also have to add --nodeps to --force for rpm to downgrade. Please don't "fix" --nodeps too!
kde was updated and systemd works for me now, but I still don't know how to downgrade with yum. I guess I would have to create a custom repo, but then yum would probably still complain.