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

[Xen]

address@hidden schreef op 23-02-2017 3:59:

> I built new systems before directly onto an array and grub just got
> taken care of by the installer.  But I never switched from one set of
> drives to another yet.

I once changed a system that was booting from a single /boot to a system 
that booted from /boot in RAID-1 (mdadm, as you) quite easily. There was 
not much to it as Andrei says.

In this case it was a GPT system. I created a BIOS boot partition of 2MB 
on both drives. Both drives had identical partition tables. Both drives 
had a ~200MB boot partition that I later migrated to RAID-1.

I guess I used grub-install on both. Both systems (both disks) 
automatically worked, because the root filesystem was also on RAID-1, 
the system booted just fine, whether the first disk was missing, or the 
second disk. Of course rebuilding may be more hard.

So in my case (This was Debian 7) I just followed a simple recipe for 
creating another mdadm array and then unpacked the archived /boot onto 
it. I probably simply installed Grub on both (/dev/sda and /dev/sdb) and 
that was all I needed to do.

Andrei means that /sda and /sdb refer to the two disks of your array.

That you need to install Grub on both disks.