I am setting up two n-boot (wherein n={2,3,4} on Dell Precision 5820 Tower workstations for development, testing, etc.

Unfortunately no Dell works with Ubuntu 16.04 if using the given (or third party) Radeon 2100X graphics card drivers from AMD, as all "roads" eventually lead back to an unreproducible config that is unsupportable, and the dreaded "login-loop" wherein the drivers do not recognize graphic-driven password inputs.

So, the osList={Ubuntu18.04; Ubuntu19.04; Debian10.x; FreeBSD12.x; DragonflyBSD5.6.x; ProjectTrident18.12}.

All three internal drives are GPT with sda=1TB, sdb=1TB, and sdc=2TB.

My sda partitions for accommodating Ubuntu are:
free space 1M
/dev/sda1 fat32 /boot/efi 746M (.73G) EFI System Partition
/dev/sda2 fat32 /biosgrub 2M BIOS Boot Partition
/dev/sda3 ext4 /boot 10240M (10G) Linux Filesystem Partition
/dev/sda4 ext4 / 10240M (10G) Filesystem Root Partition
/dev/sda5 ext4 /swap 5630M (5G) Linux Swap Partition
/dev/sda6 ext4 /usr/local 20480M (20G) Linux Filesystem Partition (for tools)
/dev/sda7 ext4 /home 768485M (750G) Linux Home Partition (for dev & test users)

This works well for Ubuntu 16.04 until I update and then the AMD-GPU issue returns.
Dell has sent me "restore" that upgrades to kernel 5.1, Ubuntu 18.04, and the correct drivers for the Radeon 2100X. I am ready to dig into grub next, however, I am 'vacant' when it comes to understanding necessary answers to the following questions:

1) is the one /boot/efi partition all I need on any of the three drives?
2) is the /biosgrub required for each OS drive or do I point back to the one at sda2?
3) how best do I facilitate that grub will differentiate between OS-specific areas?
does defining all of my mount-points "by-uuid" for sda, sdb, and sdc take care of that?
4) any knowledge I have not even foreseen that I need to know.. provided by kindly-shared wisdom.

My sdb and sdc partitions are currently data-free, awaiting revision.
I am uncertain about which partitions are required , where the bootloader is expected, and how to keep the 2nd and 3rd OS installs from overwriting the sda bootloader if I am supposed to use it (which is somehow supposed to "learn" about them at boot time, providing a menu-list of options.

Many regards and thanks-in-advance.
"frank"

Presumably this machine is EFI based. I recommend you only install/boot in [U]EFI mode - never use CSM (legacy) mode. I'm not sure how BSD handles this - never bothered with it since a brief dabble with OpenSolaris years ago.
If this is true, you only need one EFI partition - might need to be bigger than that - maybe not. You don't need the BIOS boot partition.
UUID will sort out any partition location issues.
Later installs will usually change the default boot to itself - I see you have efibootmgr as a tag; easy enough to use that to re-assign the default as you desire.

Just go ahead and do it - much easier to manage/fix these days with EFI.

I don't do multiple drives, but I think all you need is one efi partition on one drive, not on every drive.


The bios-grub partition is only needed if your using grub as the bootloader in legacy mode. Booting in efi mode the bios-grub partition isn't used at all.


If I understand this correctly yes uuids should to the trick.

The last time I installed freebsd in efi mode on a multiboot system freebsd overwrote my efi partition.

do you really need multiboot?
other distros could be installed in a VM
I guess it depends on what work you will be doing

it might also be worth looking into lvm2 ( Logical Volume Management )
with that you could do a VM or a real boot.

since you have 3 drives,
you could have some LVs setup as 3 drive mirror for max read, or stripe for read/write boost.
you could still do that with regular partitions, but lvm2 is so much easier to change things than traditional partitioning.

Hey really it's helps me a lot. Thanks for sharing such useful information. Now am clear about my topic. And you makes me easy to understand this topic. Thank so much.

https://i.dell.com/sites/csdocuments...Spec-Sheet.pdf shows no "Radeon 2100X". Are you sure you typed the X in the right place?

Since release of 16.04, the propriety of AMDGPU Pro drivers has been changed. If you plan to use 18.04 and newer releases, you should plan to use only the FOSS AMDGPU DDX provided by the distro release, along with the default amdgpu kernel driver.

Having more than one ESP partition in a system, generally speaking, is asking for unnecessary complication. How much complication depends on the particular PC BIOS implementation, and on the Grub EFI version(s) in use, and the installed operating systems. The drawback with only one ESP is what obviously will not happen if the drive that contains it fails. IMO, keeping each OS on a separate drive is another unnecessary complication. There are reasons in favor of that configuration, but none I chose to embrace. All my 20+ systems are multiboot, most with far more than 3 installed operating systems.