[NTLUG:Discuss] questions about intalling Grub and MBR

[william jones]

Ed,

You may end up with a Grub MBR on each disk with a Linux distribution.  Grub will not overswrite an existing MBR unless commanded to do so, leaving all others as they were.   At boot time, the /boot/grub/menu.lst should the one associated with your Grub splash screen.  Then it should, per menu.lst, go to the /boot directory for the chosen distribution and boot it.  /boot/grub/menu.lst must be set up so that no matter which distribution gives the boot splash screen (normally the last distribution loaded), it will boot the distribution of choice.  Two Linux distributions can be fun.  Three may try your sanity.  Typos can upset everything, and any update may change the distribution that supplies the splash screen.  Sometimes shutdown or halt commands will change the splash screen.  It is a pain keeping all the menu.lst files coordinated.  There are different ways to make Grub work, but I lack a spirit of adventure, and fear warnings that something night destroy my system and
 sanity.

WLJ  (I dislike top posting, but that is how this thread is working.)


----- Original Message ----
From: Ed Leach <ntlug at levelofdetail.com>
To: NTLUG Discussion List <discuss at ntlug.org>
Sent: Monday, April 16, 2007 5:05:23 PM
Subject: Re: [NTLUG:Discuss] questions about intalling Grub and MBR


William,

Thanks. I did as you suggest and the machine booted to an MBR on 
/dev/sdb that knew nothing of /dev/sda. I can't boot to /dev/sda by 
itself. (I have Fedora on /dev/sda and am installing Knoppix on 
/dev/sdb. No Windows.)

So, if I have 3 hard disks each with Grub on an MBR and install a disto 
on a 4th hard disk and let it install Grub on its MBR, the installer 
will go to the other 3 HDs and blow away the MBR on each one? This does 
not seem right. (Master means Master of the machine?)

I wonder also if it is safe now to manually reinstall Grub on /dev/sda/ 
and see what happens. This is a test machine, so I wouldn't lose anything.


william jones wrote:
> ----- Original Message ----
> From: Ed Leach <ntlug at levelofdetail.com>
> To: NTLUG Discussion List <discuss at ntlug.org>
> Sent: Monday, April 16, 2007 3:23:32 PM
> Subject: [NTLUG:Discuss] questions about intalling Grub and MBR
> 
> 
> If I have a distro with Grub on the MBR of /dev/sda and then I install a
> different distro on /dev/sdb and select to install Grub on the MBR, will
> it install to the MBR of /dev/sda or /dev/sdb?
> 
> If it installs to the MBR of /dev/sdb then I assume the machine will
> boot as before - finding Grub first in the MBR of /dev/sda.
> 
> Is this right?
> 
> Thanks,
> 
> Ed
> 
> Ed, 
> 
> Careful here, you are headed for a swamp.  When installing a new OS, it will override the original Grub.  Pay attention to the screen to find out whether it goes to sdb or sda.  It might be an option offered at installation time.  Best advice is to put Grub on MBR of /dev/sda.  Preparation is needed.  The new Grub does not know about the original OS.  Before installing a new OS, go to the original OS. Find /boot/grub/menu.lst. Copy the small set of lines starting with Title: Whiz-Bang Linux (or whatever distribution you have).  These lines will have to be added to the /boot/grub/menu.lst in the new OS.  After booting the new OS, find the same set of lines for the new OS, starting Title: Super New Linux (or whatever).  Patch these back into the menu.lst of your old OS.  Both distributions should be maintained with downloaded upgrades.  Sometimes these upgrades will switch the Grub being used without notice.  Be prepared.  If you also have W* XP installed and working, the
 new

>  OS should include it in the new Grub.  Watch the screen instructions during installation, and do not be afraid to scrub the new install and start over.  The screen instructions will inform you when the "point of no return" is reached.  After this, your disk is being written and everything will be what you commanded, whether you really meant it or not.
> 
> William L. Jones    
> 
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