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I have a SATA disc with several partitions, one with Centos and one with Clonezilla Live. Grub sees both entries correctly, and starts either OS correctly.

Then I install my big monster (a bit of sarcasm here) data hardware RAID (which bios and I'm assuming grub too, see as one HD), and pop! the grub does not load either OS. I disconnect the monster, and pop! it all works again.

The issue here, I think, is that grub does not map the (hd*) to either HD correctly. I don't know what order criteria there is within the grub HD detection, but it maps the monster RAID as hd0 instead of the usual SATA disc.

How do I influence the GRUB HD detection/mapping, so that grub will point the right hard drive, irrespective of whether the RAID drive is installed or not?

map (hd0) (hd1) does not solve the problem.

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migrated from Aug 9 '13 at 15:52

This question came from our site for system and network administrators.

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GRUB has map file /boot/grub/

If your RAID is going to be permanent installation - than just remap your drives in this file and reinitialize GRUB setup.

Solution for the problem is to use persistent names for your block devices. With persistent names there should be no problem with what device is /dev/sda1 or /dev/sda2, etc, because we are using unique values to identify our partitions. These values remain same regardless of other factors.

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I saw that file, but thats not the distincting solution. The file only contained which hd* mapped to which /dev/sd*. The RAID monster can still be either hd0 or hd1, or /dev/sda or /dev/sdb. – Florian Mertens Aug 9 '13 at 19:20
So, than solution would be to make RAID monster to appear at the end of the list (not /dev/sda or /dev/sdb but /dev/sdc let's say). Do you have any tools in BIOS to do that (like Hard Drives order or similar)? – VL-80 Aug 9 '13 at 19:23
Then I have two questions: 1. How can grub know about the bios preferred order list of devices if all it gets is the processing pointer; 2. Surely the bios won't boot into grub, if it booted first in the RAID monster (which would fail as theres no boot or os) or at least the boot order could not be defining anything here; so are you implying that grub receives some sort of device order outside of grub? It's my impression that some looping device analyser subroutine within grub would define the order.. – Florian Mertens Aug 9 '13 at 19:59
@FlorianMertens, good questions, actually. I just found that. There is reference on this article which can help you. – VL-80 Aug 9 '13 at 20:19
I think you are hitting my problem, yes. The forum thread is exactly what I'm experiencing, and the Persistent block device naming might become my solution that I yet have to try out.. – Florian Mertens Aug 9 '13 at 22:01

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