CentOS - Jan 2006 - Installation sequence for 4.2 / 3.6 dual boot

Hello,

I have a Dell 1850 with dual Xeon procs and two u320 36Gb drives. I
would like to set this up as dual boot system with 4.2 on disk 0 and 3.6
on disk 1.

I imagine that I would install 4.2 first and then 3.6. Would I need to
remove the other hard drive while installing a given version?

Any gotchas?

How about setting up GRUB? Anything special or does the install take
care of it?


Thanks,

Bruce McPeek
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On Fri, 2006-01-20 at 11:23 -0800, Bruce McPeek wrote:
> Hello,
> 
> I have a Dell 1850 with dual Xeon procs and two u320 36Gb drives. I
> would like to set this up as dual boot system with 4.2 on disk 0 and
> 3.6 on disk 1.
> 
> I imagine that I would install 4.2 first and then 3.6. Would I need to
> remove the other hard drive while installing a given version?
> 
> Any gotchas?
Don't run the CentOS-4 fsck on CentOS-3 or vice versa.
> 
> How about setting up GRUB? Anything special or does the install take
> care of it?
> 
I personally would not use a shared /boot partition for both OSes ... as
ext3 from CentOS-4 is different than ext3 from CentOS-3 (There are
SELinux / ACL extended attributes in CentOS-4 ext3 partitions).  I don't
even write to CentOS-3 partitions with CentOS-4 ... but that is just me.

You can easily do something like this in Grub (which is what I do on
dual boot machines):

Pick one OS as Master ... say, CentOS-4.  You would install it first,
and during the install, make it write grub to the Master Boot Record
(MBR). {This is the default}

After booting to CentOS-4, edit your /boot/grub/grub.conf file and make
an entry like this:

title CentOS-3 on Drive2
      rootnoverify (hd1,0)
      chainloader +1

Also find and remove (or remark out with a #) the line that says:

hiddenmenu

Then boot from the CentOS-3 CDs and install CentOS-3 ... keep all the
CentOS-3 install on the second drive (well ... you could share the swap
file from CentOS-4, but don't share /boot {or any other ext3}
partition).

During the CentOS-3 install, select the "Advanced Boot Loader Options"
on the Boot Loader Configuration page ... and then for "Install Boot
Loader Record on:" pick the 2nd choice {/dev/????? - First Sector of
boot partition}

See this install page in the docs for pictures:
http://mirror.centos.org/centos/3/docs/html/rhel-ig-x8664-multi-en-3/s1-x86-bootloader.html

This will allow you to select the "CentOS-3 on Drive2" and boot it ...
or to boot the initial CentOS-4 install.
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