Re: How to boot second grub?

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Scott Talbot writes:

On Sat, 2005-04-30 at 11:23 -0400, av1@xxxxxxxxx wrote:

Very sorry, my finger hit "send" too fast and I forgot to type a subject. I've been able to set up two FC3's with a single grub, but what I'd really like to do is set up a second grub and have the first chainload to the second. (I want to play with custom kernels on the second.) I have two ide's, hda and hdb. My first fc3 is on hda. I tried installing the second fd3 with /boot on hdb1 and / on hdb2. I told anaconda to put the second grub on the mbr and used the advanced bootloader screen to reorder the drives so it would write it to hdb instead of hda. After installing, I went to my first grub.conf and added title Second Fedora
rootnoveriy (hd1,0)
chainloader +1 But when I reboot and select Second Fedora, I get Error 13 invalid or unsupported executable format. What did I do wrong? What's the right way to set this up? --Cliff


Cliff:
    You need to have a copy of grub in the /boot directory (or / if you
didn't make a new /boot).
    assuming grub's hd1,0 is = to hdb1 you'll want to boot into your new
FC3 and perform grub-install /dev/hdb1
    You now won't be able to get to your old install, so you'll have to
boot a rescue cd, chroot into your old install, and perform the grub-
install to wherever that bootstrap is (/dev/hda is the MRB and the most
usual place).
HTH
Scott

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av1@xxxxxxxxx wrote:

Thanks for the info, Scott. Unfortunately I'm still stuck.
When I installed the second fc3 on /dev/hdb, I did tell the installer to put a grub on the first sector of the root partition on /dev/hdb. (I installed the second fc3 in one partition instead of separate / and /boot partitions.) I booted the first fc3 and temporarily mounted /dev/hdb1 to see what the installer did. It did install grub in /boot/grub on hdb1.

It gets weirder though. I took your suggestion of running grub-install /dev/hdb anyway. (On the theory the installer copied the grub files but did not set up the first sector of hdb.) Now when I boot the machine, and it tries to boot the original grub on the mbr of hda, it goes into an infinite loop printing "GRUB GRUB GRUB GRUB..." across the screen. Looks like I'll need to boot into an emergency Linux from the CD and figure out what went wrong.
Maybe I missed something. Starting from square one, with a clean fc3 on /dev/hda, and an empty, unformatted /dev/hdb, I'd like to do this: install a new, self-contained fc3 with its own grub on /dev/hdb, and chainload from the first grub on hda to the second one on hdb. What's the right way to set up the second fc3 so I can do this?
Thanks for your advice
--Cliff

Okay, I think I got this: boot into the rescue cd it should find both fc3 installs, choose to run the newer fc3. Follow the screen instructions to chroot into that environment. when you get to the prompt type grub-install /dev/hdb1. Reboot into the rescue cd and select the origional FC3, again following ithe screen chroot into the origional environment ant issue the command grub-install /dev/hda. You should now be able to boot into your origional FC3, and if your grub.cof is good also into your new FC3 too!

I think the problem was that you told grub to install to /dev/hdb instead of hdb1 these are not the same place! A HDD has first a MBR just a couple of sectors for the partition table and startup code, Each partition has it's own PBR for the code the local OS needs to startup (I believe grub stores the stage 2 here, stage 1 goes in the MBR). I am not a complete expert on this area, but I got a pretty good hold on it anyway as I have always at least three distros on my machine 8-)

HTH

Scott


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