Multiple distros, location of the /boot partition and kernel updates

Jongi · 08-03-2006, 10:52 AM

Until recently SUSE 10 was my main OS while I was getting to grips with FC5. The way I had set up the system was that each distro had it’s own /boot partition and grub was booting off the SUSE /boot. What this was doing was that when I updated the FC5 kernel I would then have to manual update the menu.lst file under SUSE to include both the new and the old kernel.

And to my first question: I assume that there was nothing I could have done to ensure that a kernel update of FC5 had written the changes to the menu.lst under the SUSE install?

I currently have FC5 as my main OS and have also installed Ubuntu. This time grub uses the FC5 /boot and menu.lst. So I assume that if I upgrade the Ubuntu kernel I will have to manually update the menu.lst under the FC5 install.

And so to my second question: How do I create a new /boot partition and yet not mess up the booting of FC5 and Ubuntu?

Third one: Will creating a separate /boot partition actually solve the problem of having to manually update menu.lst?

pljvaldez · 08-03-2006, 12:15 PM

If you want to really fix this problem, what I typically do is only create a /boot partition for the first linux distro and install that grub to the MBR. Then for all the other distros, I just install grub & /boot to the / partition. Then use the first grub to chainload the second one.

For example, in your case, you would use SUSE's grub to chainload FC's grub. Then if you update FC's kernel, it will update the FC grub menu.lst. But Suse's grub doesn't care because it's going to load FC's grub.

Your partitions might look like this

Code:

/dev/hda1  /boot  -- Suse's boot
/dev/hda2  /swap
/dev/hda3  /  -- Suse
/dev/hda5  /  -- FC5
/dev/hda6  /  -- Ubuntu

A typical grub entry (for your Suse grub menu.lst) looks like

Code:

title     Fedora Core 5
root     (hd0,3)
chainloader +1

Jongi · 08-03-2006, 03:21 PM

That sounds like exactly what I want to do. But then how do I migrate the /boot from FC5 to it's own /boot without screwing being able to boot FC5 at the least?

pljvaldez · 08-03-2006, 03:55 PM

That may be a little tricky. Hmm. Maybe you can boot a Live CD then

Code:

1. Mount the FC partition
2. Create a new /boot folder under the / partition
3. Copy the contents from the old /boot to the new one (maybe for now rename the /boot/grub folder to /boot/grub.old or something because I think the later "grub-install" command will recreate /boot/grub)
4. Edit /etc/fstab for the FC / (so you want to edit /mnt/temp/etc/fstab or wherever you mounted it).  Comment out the /boot line and save it
5. chroot /mnt/tmp (or whatever your mountpoint is for the FC / partition)
6. grub-install /dev/hda3 or whatever partition has the FC /
6.b. Check the menu.lst and make sure it looks right to boot FC (i.e. the kernels and root line look like the right partitions are referenced, etc)
7.  exit and unmount partition
8.  Mount the Suse partition and edit the menu.lst to chainload FC
9.  Exit and unmount suse partition and reboot
10. Select FC and hope it works...

Granted I've never tried any of this, but it seems like a logical progression to me of the things you would have to do to make it all work... In any event, I'm sure someone here can help you get it all up and running again even if you hose it up a bit. Good Luck!

pljvaldez · 08-03-2006, 04:00 PM

Ooops, just realized that I'm doing the opposite of what you want. You want to create a separate /boot partition. So just modify the above instructions to suit you.

Create the new partition and copy all the files from FC's /boot to the new /boot partition. Then instead of commenting out the line in /etc/fstab, you'll want to add a line

Code:

/dev/hdaX  /boot  ext3  default 0 0

I believe when you do grub-install you'll want to pick the NEW /boot partition, not the FC / partition.

Not sure if you have to rename the old /boot to /boot.old or something, but it probably wouldn't hurt.

Jongi · 08-03-2006, 05:15 PM

I will take your conceptual thinking to see if it marries mine