grub problem

[Rashkae]

Rashkae wrote:

>>
>>
> 
> How was the raid array created in the first place.  Was it set up as
> part of the installation, or did you use mdadm from a live cd of some type?
> 
> When mdadm creates a raid array, it encodes the 'hostname' of the pc
> into the raid array.  The theory is, if the raid array finds itself in a
> different pc, it mdadm refuses to automatically assemble it, so that
> raid devices don't get mussed when hard drives are being moved from
> system to system.
> 
> Unfortunately for this great plan, the Ubuntu initramfs, which must
> assemble any raid array for your root device, has a blank hostname.
> Therefore, if you create a raid array for root when you are booted into
> a fully operational system, that raid array will not assemble when you
> reboot into initramfs. (major catch 22)
> 
> To fix it, you have to assemble the md0 from the busybox shell.  So from
> busybox, try something like this:
> 
> mdadm assemble /dev/md0 /dev/sd?? /dev/sd??  --update=homehost
> 
> Assuming busybox is able to find all your hard drives, and you don't
> have some other kind of really bizare problem happening, that should
> start your md0, and will update the homehost information needed in the
> superblocks for automatic assembly to happen in future reboots.
> 
> 
> 

After reading the man page, (but not having tested this myself) it
appears as though the proper command to issue in busybox shell is:

mdadm --assemble --scan --auto-update-homehost