recent kernel upgrades damage mbr
Mikkel L. Ellertson
mikkel at infinity-ltd.com
Wed Jun 18 15:23:22 UTC 2008
Gene Heskett wrote:
> On Wednesday 18 June 2008, Mikkel L. Ellertson wrote:
>> This is not going to help, because the old MBR will be pointing to
>> the wrong location for stage 1.5, so you will get an error on boot.
>> Remember, the part of GRub that is in the MBR loads from a fixed
>> disk location. It does not read the file system. So, unless stage
>> 1.5 is in the same place on the disk, (head, cylinder, sector) it is
>> not going to be able to load it.
>>
>> Your best bet is to fix the device map, and run grub-install.
>>
>> Mikkel
>
> I have Mikkel, twice, and grub-install (or one of its friends) overwrote it both
> times. Lets just say it was "educational". I now have backups under other
> names there.
>
> --------device.map--------
> # this device map was generated by anaconda
> (hd0) /dev/sdb
> --------------------------
> No mention of any other drives seems to be allowed, and there are 2 others.
>
This is strange, because grub-install is not supposed to change the
device map unless you use the --recheck option.
> Also NDI why it says Anaconda, cuz Anaconda hasn't been exec'ed on this box
> since last February when (I think nvidia blobs had something to do with it)
> when something, for the 2nd time in 3 months, wiped the mbr from the boot
> drive. Now I'm on an old ATI card running the radeon driver, and no further
> problem (knock on wood). Maybe, if and when I get around to building another
> box, the new mobo's bios won't be so fscking brain dead and I won't have to
> screw around with this anymore.
>
I forgot - one other thing that may help is to change
/etc/sysconfig/grub to match what you need in the device map. That
may be where the changed device map is coming from.
> While we're on the subject of mbr's, how big is it? The first 512 bytes of the
> one I just saved is virtually empty. So I overwrote it with a 4kb version,
> but that is bearing some resemblance to a list of inodes.
>
The MBR, including the partition table is normally 512 bytes. If it
is empty, then you may be using the wrong device. Did you use
/dev/hda1, and not /dev/hda? Writing 4kb can lead to file system
corruption.
Mikkel
--
Do not meddle in the affairs of dragons,
for thou art crunchy and taste good with Ketchup!
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