[CentOS] Rebuilding Raid 1

[Mace Eliason]

Can anyone answer this question:

What happens if one drive is out of sync with the other.  One drive has 
1 month newer files on it, but its not the boot drive.

If I let Centos boot from the older version will it automatically 
rebuilt the raid 1 to the second drive?????  (bad for me)

Or do you have to manually do it??

Thanks

I am attempting to copy all the files from the newer drive to the other 
drive via a ide drive.  Then it will boot with the newer files.  Then I 
can sfdisk form the new to the other and make it bootable, then get ride 
of the bad drive.

I am so confused.


Peter Farrow wrote:
>
> Sorry I missed out the link in my original response, 
>>> you might find this article useful:
> http://beau.org/pipermail/whitebox-users/2006-April/007467.html
>
> P.
>
>
> Mace Eliason wrote:
>> 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.
>> succeeded
>> Running "install /grub/stage1 (hd0) (hd0)1+15 p (hd0,0)/grub/stage2
>> /grub/grub.conf"... succeeded
>> Done.
>>
>> do I need the device line first?
>>
>> Thanks
>>
>>
>>  
>>
>>
>>
>> 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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>>>>
>>>
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