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To boot a broken openSUSE 11.4 (also dual-linux bootloader issues)

Posted 01-28-2012 at 03:31 AM by rainbowsally
Updated 08-06-2014 at 10:33 AM by rainbowsally

To boot a broken openSUSE system:

Use the DVD. (I am not online when I do this but it should work either way.)

1. Select "install" at the main menu, then when you get to the menu,

2. Select "update" <- IMPORTANT! If you don't click on 'update' it will destroy your home folders at the last step. Reboot (reset is fine here) if there's any question and run the installer again.

Evaluating the root partition is ok. It only reads it and mounts it. (Don't freak out.)

3. Don't select any packages. The updater should only show a couple of packages (possibly none at all) when you get to the point where it tells you it's ready to 'install' those packages. A few packages to install is ok, even if you selected none. They may be configs, and I think usually are in the range of about a hundred K or a bit more.

You can stop the process at any point before the actual installation begins to verify that YOU have control. Proceed at a pace you're comfortable with. Confidence comes slowly, and sometimes at great pain. But when the choices are between losing everything and a chance to get it back, the element of "fear" diminishes significantly.

ENJOY! :-)

[And I think you will. This has only failed on me once that I recall. I accidentlly hit the wrong key and fsck-ed a mounted root partition. Woops.]

For dual linux users:

If you have an older linux installed along with your newer openSUSE do NOT use the update trick above if it wipes out your old bootloader unless you've saved significantly more than 512 bytes of mbr. (More on this below).

How can you tell if it will clobber your other linux? If the old linux saves 512 bytes or less of the mbr data, openSUSE 11.X (and almost certainly 12.x) will clobber it if it ever installs the bootloader twice. The second time it writes the bootloader will be fatal to the older linux. (Other distros have the same problem -- I wish they would be as nice to linux as they are to Windows.)

You may need a rescue CD to get back into your older linux and you probably want to make a copy of 17 or 18 sectors of /dev/sda at a point in time when both linuxes are bootable. Your guess as to the correct number of sectors is as good as mine.

See this file: /var/log/YaST2/y2log_bootloader

17? 18? Place your bets. The older bootloaders use "1", and "1+17" (see the file) = 18, so I have placed my bet on 18.

I use this script to load and run my mbr save/restore functions. No guarantees it will work on any other system. I won't even guarantee it will work on other openSUSE 11.4 which is what I have.

file: mbrfun.sub
# type 'source mbrfun.sub' to load
function mbr_backup # mbr_file
  dd of=$1 if=/dev/sda count=1

function mbr_write # mbr_file
  dd if=$1 of=/dev/sda count=1

function mbr_help
echo "
    mbr_backup # to_filename
    mbr_write  # from_filename

mbr_help # show now
I keep this in my /boot folder of my older linux which I can boot by way of... the old suse 10.0 "boot installed system" button in the installation DVD. (A rescue CD also works.)

This is a desperate measure for desperate times. Works for me. That's all I can assure you of. If you need it, good luck. Let us know what you did and how it worked out for you.

For any openSUSE user:

Remember when?

Why did they remove the button to just "boot installed system"?

Oh, I know. I've heard it many times. "Normal" or "most" users don't need that, and "normal" or
"most" users don't DO that.

Of course not!

And where are we Linux folk on the bell curve? Don't you know that "most users" use Windows?

PS. to boot other broken linuxes, a utility like ubcd "ultimate boot CD" with super grub2 can locate all bootable partitions and even boot into iso images.

There are other rescue cd's around but I haven't tried 'em. I have tried ubcd, though.

Thank you for the blog LQ.
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