[gentoo-user] MBR & GPT dual compliant format

[James]

Hello,

I thought I'd post a new thread on this issue. My goals is to have a single
default partition scheme on a sata disk that allows me to use either
Bios(mbr) or EFI(gpt) systems on these drives. Also  the goal is to keep the
partition scheme unchanged (boot;root;swap;'usr/local') but be able to set
up different file systems  and distributed file systems on these drives to
facilitate testing a wide variety of cluster architectures. I'd sure
appreciate some 'thinking outside the box' ideas for these mostly 2T sata
drives. I intend to only use one bootloader (grub legacy) but that is 
not a fixed limitation. /usr/local will be the only storage if one of these
drives is used for secondary or additional capacity, thus preserving the
partition scheme.

Here is the essences of what Neil posted before::

You can use gdisk and a GPT whetheryou are using BIO or EFI. The 
difference is in your first partition. For EFI it must be type EF00 and 
formatted with FAT. For BIOS booting you need to start the disk with 
a small BIOS compatibility partition of type EF02. This is 1M here and you
don't format or use it, it just has to be there. And.

I'm not sure it can be done. BIOS needs an EF00 partition at the start.
EFI calls for an EF00 partition, which is recommended at the start but I
don't think it's compulsory that it is there. I have heard of people
using sda2 as the ESP where sda1 is a Windows rescue partition. So you
may get away with

p1 EF02 partition
p2 EF00 partition, formatted as FAT and mounted at /boot
root and swap partitions as you see fit.

You could try it and see, but I'm not sure it could be guaranteed to work
on all EFI hardware, although it should work on all BIOS hardware........

I'd use gdisk to set the partition type to get the partition table listing
to include :: (EF02, EF00)?

This doc seems to suggest there is a way to configure such disks [1], as do
other docs I have read, but do not give explicit examples just how to do this.

So is at [1]:
https://wiki.manjaro.org/index.php?title=Some_basics_of_MBR_
v/s_GPT_and_BIOS_v/s_UEFI


Now, I should use GPT (gdisk) and label and setup the disk complete with a
gpt labeled table, but preserve the MBR for legacy booting of most bios
based systems? If that is correct, then here is what the partition scheme
could look like, for a 2T drive::

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048          411647   200.0 MiB   EFO2  FAT
   2          411648       270747647   128.9 GiB   8200  Linux swap
   3       270747648      1859022847   757.3 GiB   8300  Linux filesystem
   4      1859022848      3907022847   976.6 GiB   8300  Linux filesystem

Maybe someone can edit this table and show me an example (no worries on
boundaries or sizes) and include a few sentences to explain and guide me
on this effort?


curiously,
James