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Re: Reinstalling grub?



On Tuesday 10 October 2006 21:37, Knute Johnson wrote:
> >On Tuesday 10 October 2006 20:41, Knute Johnson wrote:
> >> I have WinXP installed on the first hard drive and FC5 on the second.
> >>  I was using grub as the boot loader but it was destroyed when I had
> >> to reload Winblows.  I'm sure that I can start FC from a CD and mount
> >> the second drive but how do I reload grub?  Any pointers would be
> >> greatly appreciated.
> >>
> >> --
> >> Knute Johnson
> >> Molon Labe...
> >
> >Put the 1st FC5 disc in. Choose Linux-rescue. You will be presented with
> >harddrive options. Choose the one that has FC5 on it, and you will end up
> >with a command prompt. Type. chroot /mnt/sysimage.  Now you can reinstall
> >Grub on the Winblows drive. If Winblows is using hda, type.
> >grub-install /dev/hda .  If all goes well, Grub should now be installed in
> >the MBR of the Winblows drive. Reboot, and you should have Grubs menu
> > back.
> >
> >Nigel.
>
> I'm with you Nigel but how does grub know that the Linux drive is
> hdb?
>
> Thanks,
>
> --
> Knute Johnson
> Molon Labe...

Mainly because if you have 2 harddrives, and Windows is on the first one 
(hda), Grub is not going to be on that, as it's a linux bootloader.

Say for instance you only had one harddrive. You have installed Windows first 
on the drive, so it is labelled as hda1, and boots up using the windows 
bootloader, using ntldr. You now install FC5 on the same drive (presuming 
that you have free space on the drive). You create a / partition for FC5, say 
this is hda3, and a /home partition hda4. Grub is waiting to be installed 
somewhere, and you are given options as to where you want to install it 
during the OS install. The default option is the MBR, and if you go for this 
Grub will be installed in the MBR of hda (where windows was booting from), 
but will add a chainloader entry to /boot/grub/grub.conf , so that you can 
not only boot up FC5, but Windows too, as you know.

If you had to reinstall the Windows OS (a common occurence) , the MBR would be 
taken over by the Windows bootloader (ntldr), and now you need to reinstall 
Grub on the MBR (the situation you find yourself in). 

You now load the 1st FC5 cdrom, and type linux-rescue. this will give you 
options for the harddrive partition you want to work with. You know that 
Windows is on hda1 so thats not the correct option, as Grub isn't on that. 
The only other option should be hda3, which is the / partition for FC5, and 
Grub is set up on that, but not installed to be used as a bootloader at the 
moment. 

Back to the linux-rescue disc, choose hda3 as the harddrive partition, which 
will get you a command prompt. Type. chroot /mnt/sysimage . this will get you 
another command prompt. Now you can put Grub wherever you like, but were 
going to put back in the MBR of hda where the reinstall of Windows had 
removed it from. So you type. grub-install /dev/hda  , and if all goes well 
Grub should be reinstalled in the MBR of hda, and when you next reboot you 
should get a Grub menu with options for FC5, and "other" which will be 
Windows.

I had a lot of problems with bootloaders initially when working with Linux, 
but over time I have become more clued up as how how they work. 

Post back if you still have problems in getting this working again.

Nigel.





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