Most recent update borks MBR on Natty

[leftbas]

I need help...badly. About to pull out what little hair I have.

I performed a software update this week, and when I rebooted my machine, it wouldn't boot. Instead, I'm greeted by a dark display. When I hold down <shift> to try to get to the GRUB menu, I get:

Loading GRUB
File not found
File not found

...then the display goes dark again.

I've tried reinstalling GRUB2, I've even poked around grub.cfg to see if there's anything there that might be changeable. But the file warns me not to edit it, so I haven't. The mod date on grub.conf is 2011-08-25, 19:02.

Also, when I try running either grub-update or grub-mkconfig, it says:

error: cannot find a device for / (is /dev mounted?)

So when I chroot to my hard drive, it complains:

34: Syntax error: EOF in backquote substitution.

Then I tried this script:

http://bootinfoscript.sourceforge.net/

...with results attached. I'm not sure, but I think I might have competing core.img files.

I'm completely stumped, guys...help.

[oshunluvr]

Re: Most recent update borks MBR on Natty

Your grub.cfg looks weird to me - specifically (/dev/sda,msdos1), instead of (hd0,msdos1), but anyway...

Are you getting a grub menu when you boot? If so, have you tried one of the older kernels or safe mode?

You can edit your grub.cfg if you want to. It's advised not to because your edit will be overwritten by update-grub. It's also read-only so you have to chmod it too.

With all your re-installing and running scripts, it hard to tell where exactly you're at now. Try these commands at the grub prompt:

root (hd0,0)
kernel /boot/vmlinuz-2.6.38-10-generic root=/dev/hda1
initrd /boot/initrd.img-2.6.38-10-generic
boot

Let me know what happens.

[leftbas]

Re: Most recent update borks MBR on Natty

Thanks for the quick reply. I guess I forgot to mention that I don't get a GRUB prompt at all. If I can get it back, I can work with that, but I got nothin' right now.

[oshunluvr]

Re: Most recent update borks MBR on Natty

If ESC at boot doesn't get you the menu/prompt, likely a live CD or USB and re-installing grub properly will be necessary.

In a konsole during a live session;

sudo mount /dev/sda1 /mnt
sudo grub-install --root-directory=/mnt /dev/sda

and reboot

[leftbas]

Re: Most recent update borks MBR on Natty

I'd already tried that with Lucid, not realizing that the mounted drive is represented by a longer patch. so I figured the file system was updated. I tried this morning with a live CD of Natty, but had the same trouble.

Anything else I can try?

[leftbas]

Re: Most recent update borks MBR on Natty

Thanks for the help, but I've thrown in the towel. I just ran through Ubuntu's instructions for purging and reinstalling GRUB2, and it had no effect whatsoever. So I'm leveling my hard drive and installing 11.04 from scratch.

[Detonate]

Re: Most recent update borks MBR on Natty

Another example of why I always keep at least two distros installed on my computer on different hard drives, and a grub install on each hard drive, that way when I have a problem like this is is simple to enter the bios and select the other hard drive as the first in the boot sequence. I highly recommend this. It has saved me many times.

[oshunluvr]

Re: Most recent update borks MBR on Natty

Words to live by, Detonate!