Multi boot RHEL

I was tasked with putting Red Hat 5 and 4, 64 bit and 32 bit on one system. It has the hardware we want. I spent the entire morning learning seven ways not to do it. Adam got with me and we went over a method or two that he has used in the past.

• Install the first Red Hat.
  • Do not use Volume Groups. Use straight up partitions. This will allow the different OS version you install to find the empty drive space.
  • Leave a gigabyte or so left over for a partition that all the OSes can mount.
  • Reuse the same boot partition. You must make a backup of it before installing each version of the OS. Reformat it each time. Keep all the files safe. You will put them on the extra partition.
  • Leave one swap partition out there. They will all use the same one.
• After you have installed all the system partitions, mount the extra partition on all the systems. Then write a script that will copy the files from the /boot backup folders on that extra partition to the real /boot folder. Go in to all the backup grub.conf and other files under the grub folder and combine everything by hand. Do not touch your originals.
• Test, test, test, then test again.

Red Hat 5 seems to let you boot just fine if you copy all the 32 bit /boot stuff from both 64 bit and 32 bit in to the /boot folder. Red Hat 4 does not play well with such shenanigans. Surely, though, something will blow up down the road if you do not have the correct /boot files in place so for goodness sake, make the script and go through the trouble.

How long did this take me to figure out. Well, I took the morning to learn six different ways of doing it wrong. Just after lunch is when I got with Adam and found myself on a good track.