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Old 07-15-2017, 12:03 PM   #1
af7567
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grub 2.02 can't see disk partitions when software raid is in use


Hi,
I am using grub on my slackware64-current system, but it won't let me boot into windows. grub-mkconfig finds the windows partition OK and adds it to the list but when I try to boot into it I get the error below.
Code:
Found linux image: /boot/vmlinuz-amdk8-4.11.2
Found initrd image: /boot/initrd-amdk8-4.11.2
Found Windows 10 on /dev/sda4
done
Code:
error: no such device: 5644BC9644BC79F7.
error: disk `hd0,msdos4' not found.
error: disk `hd0,msdos4' not found.

Press any key to continue...
In the grub console it doesn't show the normal partitions at all, only the mdX ones and proc

Code:
grub> ls
(proc) (md/md1) (md/md0) (md/md2)
My disks are partitioned so that partitions 1,2 and 3 are used by Linux for the software raid and partition 4 is kept out of the raid array. I have given windows the 4th partition on the first disk (sda4) and it is installed and was working but grub now seems to hide the normal partitions because it has detected raid.

Anyone have any idea how to get sda4 bootable by grub again, even if it is just by typing the commands in the grub command line since I don't need to boot windows much so I'm not bothered about getting it set up "properly"

Thanks
 
Old 07-15-2017, 02:15 PM   #2
Laserbeak
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Software RAIDs are a tricky thing, the driver has to be loaded from one of the RAID devices before the computer can see the RAID. This probably isn't happening before you enter Grub. Even with Apple Macs you set up with an Apple Software RAID suffer from the same problem even when using some of Apple's own tools.

Hardware RAIDs can have the same problem, but usually their firmware is loaded beforehand.
 
Old 07-15-2017, 02:20 PM   #3
af7567
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Quote:
Originally Posted by Laserbeak View Post
Software RAIDs are a tricky thing
My problem isn't that grub can't see the RAID, it's that it only sees the RAID but not the normal partition which isn't part of any RAID array.

I had another look on the grub command line and can see the module mdraid09 is loaded, but removing that doesn't bring back the msdos partition table.
 
Old 07-15-2017, 02:26 PM   #4
Laserbeak
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So, you can boot OK into the RAID-based OS, but not into a separate non-RAID hard drive partition? If so, is it possible that partition went bad?

What happens if you physically detach the drives that are part of the RAID but not the one that contains your Windows partition?
 
Old 07-15-2017, 02:32 PM   #5
af7567
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Yep, that is what's happening. I can see the partition fine from within Linux, and grub-mkconfig detects the partition as a windows install OK. It is only the grub bootloader which doesn't show it.

I can't disconnect all the drives that are part of the array because the Windows partition is at the end of the first disk, that is probably why grub ignores the msdos partition table because it knows the disk is part of RAID array.

Last edited by af7567; 07-15-2017 at 02:41 PM.
 
Old 07-15-2017, 03:36 PM   #6
Laserbeak
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Quote:
Originally Posted by af7567 View Post
I can't disconnect all the drives that are part of the array because the Windows partition is at the end of the first disk, that is probably why grub ignores the msdos partition table because it knows the disk is part of RAID array.
Why not? You can leave only the first disk attached and leave the other disks that are just part of the RAID unattached. Unless it's just too much trouble to get into your hardware (which is certainly understandable in some PC hardware I've seen), it's something I'd do to try to see what's going on. Otherwise, perhaps someone more knowledgeable in Grub can help you. Perhaps someone here or maybe you should try posting to a dedicated Grub site.
 
Old 07-15-2017, 03:42 PM   #7
Laserbeak
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Quote:
Originally Posted by af7567 View Post
Yep, that is what's happening. I can see the partition fine from within Linux, and grub-mkconfig detects the partition as a windows install OK. It is only the grub bootloader which doesn't show it.
Is there a "Startup Disk" option or something like that within your Linux? Maybe if there is and you find it you can set your Windows partition as your startup disk. Or, maybe there's a command-line equivalent.
 
Old 07-15-2017, 03:45 PM   #8
Laserbeak
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You SHOULD be able to reboot specifying the drive/partition to reboot to. That's how it works on the Mac. It saves it in EFI and then uses it on startup.
 
  


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