[gentoo-user] Re: [O/T] RAID help - now won't boot

[Nicolas Sebrecht <nsebrecht@piing.fr>]

The 21/10/13, J. Roeleveld wrote:

>  Ha!  Yes, this made a difference, thanks!  With metadata 0.90 I can see the
>  same partitions I set up on /dev/md0, also on /dev/sda and /dev/sdb.

Sorry to come back late in this thread. As other contributors pointed
out correctly, the problem was RAID metadata at the beginning.

>                                                                        The only
>  problem now is that the Ubuntu server CD wants to format /dev/sda2 as swap and
>  fails at that stage.  :-/
>
>  Not sure how to by-pass this.

Yes. Most of the installers suck at that game. What I would do (already
done this way) is:
  - install the disks in another machine with virtualization capacity;
  - create the RAID 1 (metadata=0.90);
  - create a virtual machine with the built RAID as single disk;
  - boot on the CD to install any distro;
  - move the disk out to the target bare metal machine;
  - update fstab and grub if needed.

This has the advantage to not require to bypass the installer at some
stage at the price of a temporary installation of the disks somewhere
else.

>  I may
>  also try metadata=1.0 to see if this makes a difference, which also
>  positions the RAID data superblock at the end of the device:
> 
>  Sub-Version  Superblock Position on Device
>  -----------  -----------------------------
>  0.9          At the end of the device
>  1.0          At the end of the device
>  1.1          At the beginning of the device
>  1.2          4K from the beginning of the device
> 
>    To bypass the swap format you could try either deselecting the format
>    option (if it exists) or setting the partition type to something else.
>    The partition type can be set back to swap later from a livecd without
>    having to reinstall.
> 
>    Other option:
>    1 install to single disk
> 
>    2 using sysresccd create a degraded raid1 using the 2nd drive
> 
>    3 copy the partitions and date from drive 1 to the degraded raid device

What is "copy the date"?

>    4 add disk 1 to the raid

I might miss something but I guess you're going to erase the installed
system (on disk 1) from the unused disk (disk 2), here.

I believe it would only be possible by installing the system on the
degraded RAID, which will likely mean coming back to the original swap
problem.

>    5 wait for the raid device is synchronized
> 
>    6 change fstab and grub config to reflect the new disklayout

-- 
Nicolas Sebrecht