Re: Do I need to act on this warning from apt when installing grub?

[Goh Lip]

On 16/12/2022 19:21, Pascal Hambourg wrote:
> On 14/12/2022 at 12:35, Goh Lip wrote:
> > To set up bios-legacy boot on gpt partitioning properly, you will need 
> > a small partition labelled "bios_grub".
>
> 1) "bios_grub" is not a partition label but a dummy libparted flag which 
> represents the "BIOS boot" partition type GUID.
> 2) Such partition already exists on the OP's disk, so there is no need 
> to create it.

He may have the partition, but he does not have it flagged.
He still needs to do
# parted /dev/disk set partition-number bios_grub on
A simple command for a typical user to get this done is just to label it.

bios_grub - [GPT] The partition with this flag is used as the GRUB BIOS 
partition. The partition usually uses about a megabytes of space and is 
not needed by EFI-booting systems.


> > Personally, I would suggest that for gpt partitioning, boot in uefi. 
> > And in msdos partitioning, boot in bios-legacy (though that too can be 
> > booted in uefi boot - with unreliable performance).
>
> Personnally I would suggest to use GPT with both boot modes. MSDOS lacks 
> useful features present in GPT.


My suggestion is for people not well versed with the intricacies of the 
workings of grub.
I personally have both (non-OS installed) bios-grub and efi-grub with 
msdos and gpt disks in the same system and they both boot any (and I 
have many) linux OS (efi or bios-legacy) well. I just don't recommend it 
to people.


The features of GPT vs msdos are trivial to casual users, IMO. There can 
be more than enough logical partitions in msdos partitioning that an 
average user would ever need to use.



> > ps: best when issuing grub-install command, use "--target=i386-pc" in 
> > that command for boot-legacy boots and "--target=x86_64-efi" for uefi 
> > boots, especially when installing legacy in gpt or uefi in msdos
>
> Why ? The default target depends on the current boot mode, not the 
> partition scheme.

Correct. When it is booted in the correct default mode. The problem is 
many users boot up without knowing whether they are in efi or 
bios-legacy. Having the target command eliminates that error.



Appreciate your input. Regards.