Random kernel update breakage

Sam Varshavchik mrsam at courier-mta.com
Wed Aug 25 11:10:11 UTC 2010

Michael Schwendt writes:

> On Tue, 24 Aug 2010 22:29:54 -0400, Sam wrote:
>> Every once in a while, something breaks when a kernel update gets installed. 
>> It doesn't happen every time, I'd say that once in every thirty or so kernel 
>> updates, grub fails to come up after a subsequent reboot.
>> This is just a minor annoyance -- I'd have to boot the install CD in rescue 
>> mode, let it mount Fedora on /mnt/sysimage, chroot to it, and execute 
>> /sbin/grub-install -- but I'm wondering if anyone else is seeing this.
> Yes, other people have seen it, too. Years ago already.
> There used to be an old open bugzilla ticket about it. Cannot find it on
> the overview page at http://bugz.fedoraproject.org
> Could be that it has been closed because of no progress and the low
> signal/noise ratio.
> For many it isn't reproducible at all. The kernel packages don't rewrite
> the boot loader, but just modify the grub.conf file. Via /sbin/new-kernel-pkg
> and grubby.
> And from those, who are hit by it occasionally, nobody attempts at
> debugging it or collecting all the info. Dunno whether the root cause of
> the problem is known by anyone.

I think that's because nobody really knows how to debug it. At least I 
don't, for example. The boot process is an obscure bit of knowledge.

> Did you save a copy of the broken(?) GRUB in the MBR? (Would restoring
> just the MRB instead of using grub-install would have fixed it already?)
> Did you try to press keys early to enter GRUB menu and prevent it
> from booting? Or did it fail to load much earlier?

If I knew how to save the broken MBR then I would've done it. The boot 
process does not get as far as the grub menu, that is the only fact that I 
can state with 100% confidence. All my machines are configured to display 
the grub menu, with a 5 second default timeout. When this happens, I never 
get as far as the grub menu.

I'm not sure that it's the MBR itself that gets trashed, or at least not 
always. One time the machine started beeping the console bell constantly. 
Another time I ended up staring at "GRUB" in white-on-black. This time, I 
just ended up at an empty, blank, text console screen.

If there are instructions, somewhere, for saving not just the MBR, but 
everything that gets touched by /sbin/grub-install (since it's always what 
fixes things), then I'll be sure to collect and save it the next time this 

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