[CentOS] Re: Please help! boot problem

Tue May 2 01:18:27 UTC 2006
Mace Eliason <meliason at shaw.ca>

I tried this and it seemed to work but it still won't boot just gives 
error about missing partiton still

Les Mikesell wrote:
> On Mon, 2006-05-01 at 15:27, Mace Eliason wrote:
>> Okay to clarify
>> I have only hooked up the drive that is not bootable.  The drive that is 
>> bootable has been disconnected.
>> If I run sfdisk on the nonbootable drive I get
>> /dev/sda1  (id fd linux raid autodetect) marked * for boot
>> /dev/sda2   "   "
>> /dev/sda3   "   "
>> So yes it is software raid am I right.  The system has been running off 
>> this drive for almost a month, until someone rebooted the server.
>> Should I have both drives installed when I run the linux rescue?
> It should autodetect the md devices with one missing.  However
> if it doesn't find the partitions in the automatic scan you
> can try it the hard way:
> >From the command line in rescue mode:
>  mount /dev/sda3 /mnt/sysinstall
>  mount /dev/sda1 /mnt/sysinstall/boot
> Assuming those succeed:
>  chroot /mnt/sysinstall
> Look around a bit to make sure you have the right thing
> mounted, then proceed with the instructions for installing
> grub.  If that doesn't work either, try:
> grub <enter>
>  device (hd0) /dev/sda
>  root (hd0,0)
>  setup (hd0)
>  quit
> then 'exit' twice to reboot and remove the rescue cd.
>> Does linux automatically rebuild the raid when it boot?  If I do get 
>> them to boot with the good drive I don't want it to over write the 
>> current drive.
> I'm not sure about the details but I think there is a counter
> on each disk with the number of times the RAID has been stopped
> cleanly.  If it does auto-sync, the one with the higher counter
> will be the master.  If you can get grub installed and reboot
> a few times with the disk you want to stay current it should
> become the master when they are both seen - although I generally
> don't trust this and do a scsi low-level when I have a chance
> when swapping in a new drive, then make the new matching partitions
> and add to the raid after booting.