recent kernel upgrades damage mbr

Gene Heskett gene.heskett at
Wed Jun 18 14:59:12 UTC 2008

On Wednesday 18 June 2008, Mikkel L. Ellertson wrote:
>Gene Heskett wrote:
>> So yes, if it silently rewrote the mbr, it will just as silently rewrite
>> the, and this list will, whenever I do manage to get it booted
>> again, hear from one very unhappy camper.
>It should not re-write the device map, so I would report this as a
>big. The install script needs to check if there is a device map
>file, and honor it.
>> So thanks for the warning, I'm off to dd a backup of the mbr and
>> /boot/grub to a usb key and to what is now /dev/sdc in hopes I can recover
>> from such a boneheaded 'upgrade'.
>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.

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.
# 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.

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.

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, b 
but that is bearing some resemblance to a list of inodes.

Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
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