I updated from Fedora 17 to Fedora 18 Beta with fedup.
Then I followed the post-upgrade clean up guide.
It told me to run this
rpm -a --setugids; rpm -a --setperms;
and rpm broke my system.
While it ran the first rpm command, there were a lot of error messages about files not being found. That was apparently fine. When the second rpm command ran, there were a lot of messages about being unable to set permissions. Uh oh.
When I rebooted, GDM couldn't load (well, a GTK+ GUI still showed an error message). Logging in to a VT, I couldn't sudo from my user to root. I also couldn't su. Uh oh! sudo gave me this message:
sudo: effective uid is not 0, is sudo installed setuid root?The issue apparently is that rpm reset permissions without re-setting the setuid bit anywhere. Uh oh.
I could still log in as root directly from a VT's login prompt. I did that. I found the relevant bug 881835,and there they note a new rpm that should fix the problem, version 4.10.2.
NM was still able to connect to the Internet despite the lack of GUI (w00t! if it doesn't for you, try using nmcli from the command-line), so I could still use yum to install the new RPM. So, as root
# yum --enablerepo=updates-testing rpm
Then I re-ran just
# rpm -a --setperms
And suddenly everything was normal again. :)