Re: BIOS_grub GUID signature within an EFI partition?

[Goh Lip]

On 13/09/2023 18:01, Pascal Hambourg wrote:

> Yes. BIOS-GRUB in the MBR and the BIOS boot partition, EFI-GRUB in the
> EFI system partition.


Yes, this can be done. But how do we boot in one instance in UEFI and
then in another in bios-legacy?

Do we need to go to computer bios-setup each time to boot?
I have booted in UEFI a bios-legacy OS (but not the other way round) and
when booted showed it was booted in UEFI.



> A caveat is that some broken BIOS/UEFI firmware require that a MBR
> partition entry has the boot flag set for BIOS boot, and/or the
> protective GPT partition entry does not have the boot flag set for EFI
> boot (so parted disk_flag pmbr_boot won't work). My usual workaround is
> to set the boot flag on an empty MBR partition entry with sfdisk, but it
> is ugly and fragile because partitioning tools often remove it.

In my previous system, I set boot flags in *all* my efi partitions. Now
I set flag to just my own dedicated (grub) efi partition that sort of
chainload into say my systemd-boot or refind boots. But thanks for this
info.