Re: [gentoo-user] Re: Grub, gpt partitions and BIOS, not uefi thing.

[Dale <rdalek1967@gmail.com>]

Michael wrote:
> On Sunday, 28 April 2024 19:39:16 BST Dale wrote:
>> Grant Edwards wrote:
>>> On 2024-04-28, Grant Edwards <grant.b.edwards@gmail.com> wrote:
>>>> With DOS disk lables, Grub uses empty space between the boot sector
>>>> and the first partition as a location to store it's core image file.
>>>> That empty space does not exist when using GPT disk label. When using
>>>> a GPT disk label, Grub requires that you need to create a "BIOS Boot"
>>>> or "Grub Boot" partition so that Grub has somwhere to store it's core
>>>> image[1].
>>> And it bears repeating that the bios/grub boot partition only needs to
>>> be 1 or 2MB in size, is _not_ formatted with a filesystem, and is
>>> _not_ the same as either
>>>
>>>  1) The "boot" directory where the kernel images and grubs other files
>>>  
>>>     are installed within a Linux filesystem. [Which you still need
>>>     when booting in Legacy/BIOS mode.]
>>>   
>>>   or
>>>  
>>>  2) The UEFI partition that's formated with a FAT filesystem and used
>>>  
>>>     in UEFI boot mode [which you don't need when booting in
>>>     Legacy/BIOS mode.]
>> I think I got a grasp on this now.  Basically, partitions should be like
>> this. 
>>
>>
>> First spot is the alignment thing.  Usually a few MBs or so and unused.
> This is created automatically by the partitioning tool, in your case cgdisk, 
> when you create the first partition on the disk and accept the default 
> starting sector.
>
>
>> Grub boot partition with ef02 setting, not to be formatted.
>>
>> /boot partition for kernel and init thingy.  Usually 1GB or so, enough
>> for memtest, bootable rescue image etc. 
>>
>> / or root partition that is around 150GBs or so.  Enough to expand a bit
>> and includes /usr and /var.
>>
>> /home  rest of disk unless some needed for something else.
>>
>>
>> Do you recall when running grub-install what that command looks like? 
>> Lets say the Grub partition with ef02 setting is sda1, would it be
>> grub-install /dev/sda1 or just sda and it finds the empty partition on
>> its own?
> The unformatted and empty /dev/sda1 'BIOS Boot Partition' will be found by 
> GRUB when you run grub-install and it will store its core.img in there.
>
> You install GRUB's boot.img in the MBR and therefore you have to specify the 
> disk, NOT a partition, e.g.:
>
> grub-install /dev/sda
>
> This command should:
>
> 1. Install GRUB's boot.img in the MBR of /dev/sda.
> 2. Install GRUB's core.img in /dev/sda1 which you created as a 'BIOS boot 
> partition', type EF02.
> 3. Create directory /boot/grub to install all the grub fs drivers and files.
>
> If you have mounted /boot, all is well.  If you are repairing an installation 
> from a liveUSB you can mount the /boot partition, e.g. /mnt/gentoo/boot and 
> specify this in the CLI:
>
> grub-install --boot-directory=/mnt/gentoo/boot /dev/sda
>
> NOTE:  As per the link Grant helpfully posted you can create the 'BIOS boot 
> partition' with cgdisk "... by setting the partition type to 0xEF02 and giving 
> it a label of gptbios".
>
> https://wiki.gentoo.org/wiki/GRUB#BIOS_with_GPT
>

That's what I was thinking.  I think I got it.  I need to make notes of
this tho.  Before I forget.  :/ 

Thanks to all.

Dale

:-)  :-)