Created attachment 1490905 [details]
Snippet from /var/log/dnf.rpm.log

Description of problem:
TLDR; Downgrading certain glibc packages resulted in a broken fedora install. Unable to boot. Unable to chroot in from a rescue boot.

While debugging a different problem, very slow boot time because of waiting on udev and lvm2-monitor, I decided to try to upgrade to a never version of lvm2, the rawhide version.

Upgrading lvm2 dragged in newer glibc packages as well. This is shown in the dnf.log
After the upgrade I rebooted, and the boot was still almost 2 minutes long. I decided to downgrade lvm2 and everything the dnf transaction upgraded.
During the downgrade I sort of had a feeling this was not going to end up right, as there was some errors. And I was correct, nothing worked after the downgrade,  tried 'ls' and lots of other commands, but all gave the error of 'no such file or directory'. I sort of knew at this point it was an issue with the glibc downgrade.
The errors appear to be related to scripts that are run after glibc-common is downgraded.
2018-10-03T21:41:01Z ERROR Non-fatal <unknown> scriptlet failure in rpm package glibc-common

These errors are shown in dnf.rpm.log
While I don't know if it is the glic-common package which ended up breaking things it is the only one that stands out to me in the log.

Version-Release number of selected component (if applicable):
glibc-common-2.28.9000-8.fc30.x86_64

How reproducible:
I would reckon every time, but I don't know for sure as I do not want to reproduce it in fear of not being able to recover.

Steps to Reproduce:
1. Have fedora 28 installed
2. Enable rawhide repositories and import gpg keys for fedora 30
3. do dnf --enablerepo=rawhide upgrade lvm2
4. reboot
5. do dnf history undo <transaction number for lvm2 upgrade>

Actual results:
Broken system.

Expected results:
Not broken system.

Additional info:
I don't know whether this is regarded as a bug or not, since I downgraded glibc while running the system. So perhaps the scriptlet that failed is not guaranteed to work while running the system. In which case this bug report can be disregarded. I was on the fence whether I should report it or not :)