How to boot second grub?

[av1 at ansae.com]

Scott, that did the trick. Thank you very much. 

After I got it working, I went back to the beginning and reinstalled the 
second Fedora to make sure I would be able to do it again in the future. 

In case anyone else wants to do this, here is a summary of how to install 
two fc3's with chained bootloaders. 

 - install the first fc3 on /dev/hda in the usual manner 

 - install a second fc3 on /dev/hdb like this
   -- I made a single partition on hdb mounted as "/". (I bet the steps 
would change a little if you made a separate partition for /boot, but I 
didn't need to do this.)
   -- Choose to install grub. It will say it's going on /dev/hda, but don't 
worry.
   -- Check advanced bootloader options.
   -- On the next screen, choose to put grub on the first sector of the root 
partition (/dev/hdb1), not the mbr.
   -- Do the rest of the installation on hdb as usual. 

 -- When you reboot, start the first Fedora on /dev/hda. Edit 
/boot/grub/grub.conf. Add this stanza 

   title Second Fedora
       rootnoverify (hd1,0)
       chainloader +1 

(You could have done this before installing the second Fedora to save a 
reboot.) 

 -- Reboot, choose Second Fedora, and you should be in the second grub on 
hdb. 


Scott writes: 

> 
>> 
>> Scott Talbot writes: 
>> 
>>> On Sat, 2005-04-30 at 11:23 -0400, av1 at ansae.com 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 at ansae.com 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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