I have a raid-1 running under rhel6 (/dev/md0) that is mapped to /. It contains two unpartitioned disks (/dev/sda and /dev/sdb). I'd like to be able to boot from either disk. But grub won't let me do this, since it can't see a partition on either disk. I'm afraid I've rendered this system unbootable (and I don't want to reboot to find out). Any ideas on how to get out of this? I'm happy to break the raid to make that happen, if necessary.

To be more specific, running grub-install /dev/sd[a,b] leads to: Unknown partition table signature (this repeats 10 times) The file /boot/grub/stage1 not read correctly.

And running grub directly and then saying "root (hd0,0)" or "root (hd1,0)" leads to: Error 5: Partition table invalid or corrupt


I don't think GRUB will work without a partition table. If you don't mind losing the data, just repartition the drives and start over. I find it useful to make "whole disk" partitions for RAID members slightly smaller than the drive size because all drives sold as a given size are NOT identical in terms of number of sectors. If you forfeit a cylinder or two on the end, you'll be more likely to be able to replace a drive and re-add a replacement when the time comes.

  • I do mind losing the data! Well, it's more that it takes time to get a system manually deployed (setting up iptables, networking, etc.) and I'd rather not have to do that. Is there any way I can save this system? Can I remove both drives from the raid, fix their partition tables, and re-add them? mdadm won't let me remove both, but I'm wondering if there's some way to force it to let me. – clu Nov 2 '11 at 16:42
  • Yes, see my answer to: superuser.com/questions/353058/…. The "convoluted" procedure will probably let you do just about anything you need. – kbyrd Nov 2 '11 at 16:44

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