My bootloader seems to be FUBAR. Please help, I'm going mad!

MidnightCommando

Hi guys.

I've somehow managed to completely break my bootloader.

Symptoms:
- System boots up to :

maltinator · Posted: Thu Jul 01, 2010 10:17 am Post subject:

Hi Horst,

Can you download sth. the size of floppy? In that case I would recomend the Suber Grub Disk. It's 1.44Mb small an fits on a floppy and ist great for restoring demaged grubs, or gives you the possibility to manually enter a boot command. So if you know your partition table, and were you stored your kernel, you just enter your stuff und can boot your beloved gentoo.

malte
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NeddySeagoon · Posted: Thu Jul 01, 2010 11:37 am Post subject:

MidnightCommando,

grub-static is only needed by amd64/no-multilib purests. Grub is mostly 32 bit code that will not build in a no-multilib environment.
Since we can conclude that your grub built, you don't actually need grub-static, even if you were using it before.

I'm pretty sure that you have an old grub stage1/stage1.5 (in the area before the filesystem) and a new stage2 in /boot/grub.
As you say, all will be well again if you can install a grub to the MBR that matches the stage2 in /boot/grub

Grub patches its stage1 and stage1.5 during the install, so a dirty hack to fix that is unlikely - more later.
If you can boot a CD then mount your /boot you should be able to run the grub install manually.

To fix stage1 and stage1.5 you need someone with the same boot layout to donate you the first 63 sectors of their drive which contains the patched stage1 and stage1.5 that you need. It also contains their partition table, which you would not want.

You can mount some ext4 filesystems as ext3 ... it depends on the features you have used in ext4. If you try, you get an error from mount about unsupported features.
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NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

MidnightCommando · Posted: Thu Jul 01, 2010 12:06 pm Post subject:

Vielen dank, maltinator! I know my disk geometry, and where the kernel is - I can also get hard copy of my grub.conf if i use ubuntu and transcribe the file to paper by hand (Finally, a worthy and epic use for my Lamy pen ehehe).

Repair would be lovely - I'll gladly settle just for having the ability to boot, though - I'm hardly averse to using a floppy on each reboot.

NeddySeagoon, I'm glad that you concur with my prognosis - as you say, a direct transplant of the entire Master Boot Record would be undesirable at best and damaging at worst.

I have attempted to rebuild grub several times already using the canonical procedure, to no avail - hopefully the Super Grub Disk mentioned by maltinator will afford me some better luck. I'll report back if it works, or doesn't.

Regards,
-- Horst.
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MidnightCommando · Posted: Thu Jul 01, 2010 1:16 pm Post subject:

Good news and bad news. I was able to boot into Gentoo using the Super GRUB Disk ...

where i promptly rebuilt grub (just to be on the safe side), noticed the warning about doing grub-install this time around, did grub-install, rebooted to see if it worked ...

and landed back at square one.

What do, guys? I fear irrepairable damage to my 1337 system

(I can boot into gentoo manually from the grub commandline of the floppy disk - just can't seem to make grub "take" in the MBR properly it seems.)
_________________
How many kernels must a geek compile, before he is called a geek?
The answer, my friend, is blowing in the wind, the answer is blowing in the wind.

NeddySeagoon · Posted: Thu Jul 01, 2010 5:13 pm Post subject:

MidnightCommando,

If you emerged grub, we know your grub binaries are self consistent.

Since you got the same issue after you reinstalled grub to the MBR, I conclude that the install failed, or it installed correctly but to the wrong place.
You might not have noticed the fail. Many BIOS provide boot sector virus protection. When that is on, writes to the MBR appear to work but nothing is written.

How many drives do you have?
Did you have any USB storage devices attached when you did the grub install?

Sight of your

MidnightCommando · Posted: Fri Jul 02, 2010 7:24 am Post subject:

NeddySeagoon · Posted: Fri Jul 02, 2010 4:24 pm Post subject:

MidnightCommando,

That looks good, except your device.map should have a line for /dev/sdb too
delete device.map and reinstall grub to the MBR. Check that device map has been updated
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Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

dol-sen · Posted: Sat Jul 03, 2010 12:35 am Post subject:

NeddySeagoon, MidnightCommando

Just be aware that grub can build in a 64 bit environment without dieing. I just did it in an selinux kvm. IT DID NOT RUN, just segfaults. The only installation error was missed by portage because the ebuild did not have the "|| die" added to the line that runs a "/sbin/grub --batch..." command near the end of the ebuild. So portage will think all is well and installed without a problem.

Oh, if you just complied a new kernel, make sure that you still have "IA32 Emulation" selected in "Executable file formats / Emulations --->" if you run a 64 bit system.
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NeddySeagoon · Posted: Sat Jul 03, 2010 1:21 pm Post subject:

dol-sen,

That will be a bug then. I'm a /no-multilib/ 64 bit purest, so I have to use grub-static
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Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.