[CentOS] Rebuilding Raid 1

Mace Eliason meliason at shaw.ca
Mon May 1 23:41:24 UTC 2006

I just think this might work

I am using scsi drives so would I use root (sd0)  I tried it but it said 
error while parsing number

I tried root (hd0) and it said filesystem type unknown, using whole disk

I stopped at that point worried I might mess up the whole thing

I have read other links that talk about doing it this way

$ grub

grub> device (hd0) /dev/hdc
grub> root (hd0,0)
 Filesystem type is ext2fs, partition type 0xfd
grub> setup (hd0)
 Checking if "/boot/grub/stage1" exists... no
 Checking if "/grub/stage1" exists... yes
 Checking if "/grub/stage2" exists... yes
 Checking if "/grub/e2fs_stage1_5" exists... yes
 Running "embed /grub/e2fs_stage1_5 (hd0)"...  15 sectors are embedded.
 Running "install /grub/stage1 (hd0) (hd0)1+15 p (hd0,0)/grub/stage2
 /grub/grub.conf"... succeeded

do I need the device line first?



Peter Farrow wrote:
> You can replace the boot loader as follows:
> 1)Boot in REscue mode, and get a command prompt
> 2)Run grub, if your two disks are for example /dev/hda and /dev/hdb 
> and the boot partition is the first on each:
>          grub> root (hd0)
> ....
>          grub> setup (hd0,0)
> ...
>          grub>root (hd1)
> ...
>          grub>setup (hd1,0)
> ...
>          grub>exit
> This will put a stage1 boot loader on each disk, you should be able to 
> boot the originally non-bootable disk now.  Make sure you boot in the 
> bios from the second disk, (which I presume is the one you want to 
> keep), to make sure you could disconnect the original drive first and 
> boot the system to try it.
> You might find this article useful.
> If the first disk has now been fixed but contains no data, you can 
> export the partition table from the second disk using sfdisk, and 
> re-import it on the first hard disk using sfdisk again, you can then 
> use mdadm to hot add the first (replaced) disk to the second (running 
> and now bootable) disk.
> Regards
> Pete
> Mace Eliason wrote:
>> Trying a different approch.
>> Senario
>> Raid 1 setup
>> Bootable raid drive failed
>> Mirror has been working for almost a month and then rebooted
>> Now can't boot mirror drive grub not mirrored from other drive.
>> I Fixed bootable drive.
>> Question?
>> Can I hook up both drives and boot fixed drive then rebuilt mirror 
>> from nonbootable drive to bootable drive?
>> Does the raid automatically rebuilt when I boot with both drives?
>> Can I run a command to rebuilt from one drive to the other and visa 
>> versa
>> I want to try it but I am worried that if I hook them up and it boots 
>> that because the bootable drive has older info it might over write 
>> the other drive.
>> Thanks
>> Can't seem to figure out how to get the other drive bootable.
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