This may or may not be a bug. I think it is, but it might be a purposeful choice. Either way it is causing operational problems. First I am experiencing other problems with preupgrade which are being filed under other bugs or I might not have noticed this issue. The problem is that normally when you boot the server you get the option to press space bar to get a menu from which you can boot other kernels, or change parameters. I have run preupgrade and not instead I get a message about booting from cd/dvd and then it goes on. If you press the reboot button on preupgrade to then it reboots and goes into the upgrade routine. If the upgrade fails and you want to try again, or of you exit preupgrade and plan to reboot and then run preupgrade this will not work because of the no menu. Now I also don't have access to old kernels or switching to single user mode.
preupgrade does not change your grub configuration. It uses grub's '--once' flag to cause your system to boot directly into the upgrade when you hit the 'reboot' button, but this only happens once. When you reboot again your menu will appear as it did before.
That is my point when I reboot again the menu is now gone. It was there before I ran preupgrade, like maybe 1-2 hours earlier. At that time I took the system time, used the menu to boot into single user mode and did a fsck. I find this a wise precaution before an upgrade. Now the menu is gone. So something happened.
Also this boot from cd/dvd message is new, and no there is not a disk in the drive I checked.
OK I found the problem. What happened is a better question. The timeout= value in grub.conf had been changed to 0. Changing it back fixes the problem. Now I guess the question is what changed it??????