Re: Will this in-place conversion from LEGACY/MBR RAID1 boot to?? GPT/EFI boot work
At Tue, 7 Oct 2025 17:46:16 -0500 Ram Ramesh <rramesh2400@gmail.com> wrote:
>
> On 10/7/25 15:29, Robert Heller wrote:
> > At Tue, 7 Oct 2025 14:48:48 -0500 Ram Ramesh <rramesh2400@gmail.com> wrote:
> >
> >>> Yes what you've described will work except for having to shrink the
> >>> second partition a little for the backup GPT header. mdadm guides have
> >>> got you there; should be pretty simple for a RAID-1 that's not totally
> >>> full.
> >>>
> >>>
> >> As I have indicated, I am deleting everything in the disk as I convert
> >> to GPT with same size MD partition. I have about 32G of free space to
> >> work with as the current MBR partition 1 is empty/unused. So, there
> >> should be no issues with secondary table at the end. The new partitions
> >> will automatically move up a bit and RAID rebuild will take care of
> >> initializing the new partition after I clobber the disk and recreate a
> >> new GPT layout.
> >>
> >>> Most people seem to opt for having two ESPs that are kept in sync and
> >>> thus both/either are selectable from the firmware boot process.
> >>>
> >> I am not too worried about any redundancy on EFI/boot partitions as a
> >> broken EFI is easy to fix with booting install disk in rescue mode and
> >> reinstalling grup again.
> > What you should do is make EFI/boot partitions on both disks. And then
> > manually sync them -- this is not a "continious" process, just when something
> > changes (eg new kernel, new EFI settings, whatever). If the "boot" disk fails,
> > the other has a copy of the EFI stuff, so you don't need to mess with a rescue
> > disk, just swap the second disk to the boot disk position, and the system will
> > boot (with the RAID in degraded mode). When a replacement disk arrives,
> > install it as the second disk, partition it, sync over the EFI/boot
> > partituons, and do the usual RAID rebuild for the main data partiition.
> >
> >> Regards
> >> Ramesh
> >>
> >>
> >>
> Makes sense. Thanks.
>
> However, is it better to rsync the two EFI partitions or simply mount
> the second efi and grub-install creating a fresh copy of EFI files?
I've found it "trivial" to just mount the second efi and rsync. When I had
such a setup, it was baked in the daily backup script -- no manual messing
with (I don't remember if it did the rsync daily or monthly -- in sync with
monthly full backups). Once properly setup, it was something that happened
automatically and one less thing to have to think about. (I don't know if
installs of new kernels ever messed with the EFI partition -- /boot was its
own small RAID mirror set.) I don't know if rsync is better / worse than using
grub-install for a fresh copy of EFI files, other than rsync ensures that the
EFI files are *exactly* the same on both disks -- you the EFI files on the
second disk set up so that they will work properly if the "second" disk
becomes the "first" disk, which is exactly what will happen when things fail.
I didn't to delve into the inner workings of grub-install and EFI boot logic
and rsync allowed to me to avoid that bit of groveling in the documentation.
>
> Regards
> Ramesh
>
>
>
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