[NTLUG:Discuss] Grub assistance

[Leroy Tennison]

David Simmons wrote:
> 
>> OUCH!  "..reformat the Linux disk,"  just because there is
> no MBR on the
>> disk??  That's HARSH!  
> 
> Yes....all you
> really need to do is boot with some type of rescue disk and issue:
> 
> fdisk /mbr /dev/sda
> 
> http://www.novell.com/coolsolutions/qna/1742.html
> 
> _______________________________________________
> http://www.ntlug.org/mailman/listinfo/discuss
> 
Now that I've deleted the previous emails which had the grub.conf 
contents...

Some things to consider:

Read everything in a number of references before doing anything so that 
you will have a full knowledge of what is going on with grub: "info 
grub", "info grub-install", http://www.gnu.org/software/grub,

http://www.redhat.com/docs/manuals/enterprise/RHEL-4-Manual/en-US/Reference_Guide/, 
particularly sections 1.2 and the early parts of 2.

http://www.pmg.lcs.mit.edu/~chandra/install/install_dualboot.html 
(another way of looking at multi-boot)

The Grub stage1 file is written to the MBR and knows the (file system 
independent) location of stage2 (or a specific stage1.5 if necessary). 
Stage2 contains the full path to grub.conf so care needs to be exercised 
when working with the MBR, etc.

Definitely get a rescue CD for a distro as close to yours (or exact) as 
possible.  You can run into file system type and version issues if they 
are too different (older Red Hat not understanding reiserfs, older 
distro not understanding a newer version of ext3 - have experienced both 
of these).

grub-install can install to a floppy drive (if your machine has one) so 
you could boot to a floppy and manually enter the commands to start 
Linux (print out grub.conf before doing anything).

A suggested process is:

use dd to backup your mbr to removable media, you may need to restore it 
later (if you have to fall back to a two drive system then have Windows 
boot Linux and restore the MBR overwritten by MS' fdisk).

Consider using the information in the www.pmg... article to allow 
Windows to dual-boot Linux.  The issue is that the MBR points to stage1 
and, if you pull the Windows drive before running the Microsoft 'fdisk 
/mbr', stage1 won't be found: non-bootable system.

backup your grub.conf, edit it changing references to hd1 to hd0

backup /etc/fstab, edit it to make adjustments as well (might want to 
consider changing references in it to UUID rather than /dev/..., this 
avoids the drive references at least in it)

Pull the Windows drive but have it available to put back in if things 
don't go well.

Boot either to the grub floppy or the rescue CD and use setup (grub 
floppy) or grub-install (rescue CD) the make the Linux disk bootable.