Re: (Marvell) migrating RAID1 from MBR (1TB) to GPT (6TB): U-Boot and GPT?

[Ian Campbell <ijc@debian.org>]

On Tue, 2019-04-16 at 19:04 +0200, Emanuele Olivetti wrote:
> ...in my /etc/fstab I have:
> ----
> # /etc/fstab: static file system information.
> #
> # Use 'vol_id --uuid' to print the universally unique identifier for
> a
> # device; this may be used with UUID= as a more robust way to name
> devices
> # that works even if disks are added and removed. See fstab(5).
> #
> # <file system> <mount point>   <type>  <options>       <dump> 
> <pass>
> proc            /proc           proc    defaults        0       0
> /dev/mapper/vg00-root /               ext4    errors=remount-ro 0   
>    1
> # /boot was on /dev/md0 during installation
> UUID=8ecca189-7483-4324-8de2-13f6a5ad7a8b /boot           ext2   
> defaults        0       2
> /dev/mapper/vg00-home /home           ext4    defaults        0     
>  2
> /dev/mapper/vg00-swap none            swap    sw              0     
>  0
> ----
> and UUID=8ecca189-7483-4324-8de2-13f6a5ad7a8b (boot) is /dev/md0. All
> seems correct. But the system won't boot from the second 6TB disk
> alone - the one with GPT.

I don't think /boot is the one which actually matters here, it's the /
one. The initramfs should have /conf/params.conf in it which should
contain ROOT="/dev/mapper/vg00-root" I think to force that (since the
uboot config doesn't know about the Debian setup).

> Maybe initrd.img is not updated and I just need to execute "update-
> initramfs"? I expect that I don't have to manually change
> initrd.img...

/etc/mdadm.conf is in the initramfs and contains a uuid (for the array
itself?). I'm unsure if this is something which might have changed with
the gpt stuff you did?

> I'm very cautious in these steps because, as you know, it's not
> straightforward to fix a non-booting QNAP :-)

Might be a good idea to test your recovery stuff first, e.g. ensure you
have copies of the current mtd stuff and can use the recovery mode to
load them over tftp etc (that's assuming you don't have serial, if you
do it's a little easier...).

You'll probably not find many people who have specific experience of
the situation you are in, so good advice might be hard to come by :-/

Ian.