Re: How to safely switch grub booting in-place from one drive to a replacement with RAID?

[Andrei Borzenkov]

23.02.2017 18:56, address@hidden пишет:
> Hi,
> 
> On Thu, Feb 23, 2017, at 07:30 AM, Andrei Borzenkov wrote:
>> With /boot/grub on Linux MD you can install grub2 in MBR only. Run
>> grub-install (or grub2-install depending on your distribution) twice for
>> each disk
>>
>> grub-install /dev/sda
>> grub-install /dev/sdb
> 
> I just want to be sure I understand what you mean by 'each disk'.
> 
> Each Disk of the array?
> 

Correct.

> In my case that's
> 
>   grub-install /dev/sdb
>   grub-install /dev/sdc
> 
> Or do you really mean
> 
>> grub-install /dev/sda     <-------- the single, non-RAID disk     
>> grub-install /dev/sdb     <-------- only ONE disk of the array
> 
> ?
> 

If you intend to remove sda and leave only sdb, sdc as the only drives -
yes, but then it is more involved than that. Could you run
https://github.com/arvidjaar/bootinfoscript and make RESULTS.txt available?

> Oh and I just wanted to be sure about the "metadata" I can use.
> 
> I read some recent info that using RAID1 metadata == version 1.2 is OK with 
> Grub2 for "/boot" partition.  IIUC it used to not be but newer versions of 
> grub2 took care of that.
> 
> Is that right?
> 

Yes, grub2 supports all 1.x metadata variants.

>> You will also need to configure your distribution to use these locations
>> by default, so it automatically writes new version of grub into correct
>> location(s) during package update. How to do it is distribution-dependent.
> 
> I think that's done here on Opensuse with
> 
> /boot/grub2/device.map
> 

No. device.map is almost always irrelevant for grub2 installation.
Device for installation is stored in /etc/default/grub_installdevice; if
you use YaST to configure bootloader and YaST detects that /boot/grub2
is on RAID1 it should automatically configure system to install grub in
MBR of both disks.

>> You may also want to recreate grub.cfg as well.
> 
> Yeah, that one I got! :-)
> 
> Thanks,
> 
> Darrin
>