How to mount a "BIOS boot partition"?

[Giovanni Gherdovich]

Hello,

I'd like to install two different linux distributions and use grub to
boot into one or the other. I have a dedicated grub partition on
/dev/sda1 and two other partitions for the OSes. /dev/sda1 appears to
be a "BIOS boot partition" to tools like parted(8), fdisk(8) or
gdisk(8).

My question is: how do I mount a "BIOS boot partition"? Specifically,
which type of filesystem should I give as parameter to mount(8)?

Mounting such partition seems to be a requirement as per section "5.3
Multi-boot manual config" of the grub2 manual, as I'm supposed to run

    grub2-install --boot-directory=/mnt/boot /dev/sda1

<https://www.gnu.org/software/grub/manual/grub.html>

The layout of my partitions is

    # gdisk -l /dev/sda
    [...]
    Number  Start (sector)    End (sector)  Size       Code  Name
       1            2048         1060863   517.0 MiB   EF02  primary
       2         1060864         5269503   2.0 GiB     0700  primary
       3         5269504       591337471   279.5 GiB   0700  primary
       4       591337472       976773119   183.8 GiB   0700  primary

As of now the tool "bootinfoscript" says that core.img is at sector
2048 and looks for (,gpt4)/boot/grub2 (which is on /dev/sda4)

<https://github.com/arvidjaar/bootinfoscript>

I guess what I want is to have grub2 itself to be installed on
/dev/sda1; that's what I hoped to accomplish using grub2-install,
provided I can mount /dev/sda1 somewhere.

Thanks,
Giovanni

PS: Please CC me to replies, as I am not subscribed to this list.