Dual Boot RHEL 7.9 with SLES 12

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We have a requirement to setup a server that has both RHEL 7.9 and SLES 12 installed. Is it possible to dual boot RHEL 7.9 with SLES 12? If yes, what are steps to do so?
Can this be done in BIOS mode?
Which OS should be installed first?
What steps should be followed for the second installation?

Responses

Hi Dale,

Sure it is possible ... GRUB detects the other system, and you can choose which system to start in the boot menu.
The steps ? Simply install one system and then the other system. BIOS mode ? No problem. Which to install first ?
Your choice - the problem is something else : every time a kernel from either system gets an update, you will have
to update the boot configuration manually in both systems. Dual boot is an "outdated" method of running multiple
systems. I recommend to install RHEL on the server and on top SLES in a KVM virtual machine. Hope this helps. :)

Regards,
Christian

RHEL7 easily supports dual booting in Legacy BIOS mode, but I haven't used SLES in many years, so I can't provide specific comments regarding that OS.

Nevertheless, here is an overview of how I would approach this type of system configuration. It requires in-depth knowledge of the SYSLINUX/EXTLINUX bootloader, RHEL kickstart, and SLES autoyast.

  1. Define the disk partitions needed by each OS, then partition, format, and label the target disk prior to OS installation. If possible, use standard partitions instead of LVM.
  2. Use the extlinux bootloader for each OS, instead of GRUB2. Unlike GRUB2, the extlinux bootloader may be installed on the partition, not the MBR, so the RHEL and SLES installers can run without contention for the MBR. (If the MBR does get overwritten, extlinux makes it easy to recover - see mbr.bin.)
  3. Define a dedicated system boot partition, which does nothing other than provide a menu to chainload either RHEL or SLES. Again, this is easy to do with extlinux.
  4. Use RHEL kickstart and SLES autoyast (I think) to install each OS to their corresponding partitions.

For partitioning, the partitions of type "Primary" will contain extlinux, and only partition 1 should have the "bootable" flag set:

Part No. | FS Type |    Content
---------|---------|-----------------
    1    |  ext2   | System Boot Menu
    2    |  ext2   | RHEL /boot
    3    |  ext2   | SLES /boot

For RHEL installation, here is an example of the kickstart directives for a basic partition layout. (The contents of /home are preserved in this example.)

part /boot --fstype=ext2 --usepart=LABEL=R7_BOOT --label=R7_BOOT
part swap --usepart=LABEL=R7_SWAP --label=R7_SWAP
part / --fstype=xfs --usepart=LABEL=R7_ROOT --label=R7_ROOT
part /home --fstype=xfs --usepart=LABEL=R7_HOME --noformat

For SLES autoyast, I can't provide an example, and I don't know if it's even possible. If it is indeed possible, though, then you're all set.