[LAU] Multiple Linux Operating Systems on Grub, Help or Info appreciated

[Mark Knecht]

2009/4/28 Viktor Mastoridis <viktor at mastoridis.co.uk>:
>  small history,
>
> I am using Ubuntu Studio for a year now, and with the release of 9.04
> Jaunty, I decided to do a clean install of it.
> As for a long time a wanted to try Studio64, I decided to partition my hard
> disk and install that as well (Studio64 2.1)
> I also like and need Frescobaldy, but I just couldn't install it on a Debian
> platform, so I decided to make one more partition and install Open Suse
> 11.1.
> Finally, I made one more partition for future OS tests and one partition for
> the files.
> All in all, on my 500gb hard disk I created 6 partitions and installed the
> OS's in the following order:
> 50gb partition 1 : Ubuntu Studio
> 50gb partition 2: Open Suse
> 50gb partition 3: Studio64
> 50gb partition 4: empty
> 180gb partition 5: files
> 20gb partition 6: swap
>
> Now, of course, every OS created it's own boot loader and when I finally
> installed Studio64, although it recognised the other OS's, and gave me the
> option to boot into them, a Grub error 12 would appear (no files).
>
> Browsing Forums, I bumped across Grub Super Disk and I am able to boot into
> every single OS from there. But alas, I am not literate enough to create a
> valid menu.lst on the master boot record.
>
> I would appreciate any hints or (links to) simple and clear instructions on
> the net. I am ready to reinstall all the OS's if needed. I start to
> understand that a small separate /boot partition would be very useful, but I
> don't have a clue how to set it up.
>
> Viktor
>

Simplistically speaking it's a non-issue to have multiple Linux OS's
on the same system, either on the same drive or even on separate
drives. Each is accessed through an entry in grub.conf. In my
experience you have to watch out for the following sort of issues:

1) Keep each system completely independent on different partitions.
Simplistically, if everything under / for each system resides in its
own / partition, which it sounds like you've done, or if you are
careful to create separate partitions for each distros /var directory
for instance, then you can have multiple partitions for each distro.
It's just important that each distro point only at partitions that it
is using. It sounds like you've done that so reinstalls should not be
required - only possibly edits in each distro's fstab files.

2) To protect each distro in each distro's fstab file make sure you
only mount the partitions appropriate for that distro. Don't mount
Debian's /var partition when running Suse, etc.

3) To share your user data between distros it's fine to have a single
/home partition that is used by all distros, but it has to be done
carefully and it likely will not be correct immediately after the
install. Different distros will give different users unique user and
group IDs so you need to make sure they are all made identical when
using useradd and other tools like that. None the less when they are
correctly set I've not had any trouble with Fedora reading my Gentoo
/home/mark directory, etc. I can log on as mark in any installation
and they all see the same files.

4) You can use grub from any modern distro to boot all distro's that
you've installed.

5) In grub.conf you'll have different kernel command lines based on
what disk you are booting off of pointing at the right partition.
Other than that grub will look very normal.

Hope this helps,
Mark