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[SOLVED] GPT SSD now for later upgrade?
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johngalt
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PostPosted: Sun Jul 01, 2018 9:39 pm    Post subject: [SOLVED] GPT SSD now for later upgrade? Reply with quote

Hi, all,

Got a question:

My desktop is currently a Core i7 965 EE on an eVGA X58 Classified 3 mobo w/ 12 GB triple channel DDR3. The main drive is a Sandisk 960 GB SATA `III' SSD (connected to a crippled Marvell 88SE9123 chipset-controlled SATA `III' port that only offers 5 Gb/s speeds, instead of the full 6). Motherboard is pure BIOS, not uEFI.

I've read several posts on what users have been advised to do when installing on a BIOS-based mobo and have (inadvertently) used GPT on their boot drive. I also attempted the same myself, foolishly forgetting that this machine is, in fact, BIOS and not uEFI - Fat lot of good it did me when I was attempting to install GRUB2 and it refused to (lack of unused space at the beginning of the HD).

But, I've been mulling over a concept that should, theoretically, work - setting up a system now that is, in fact, capable of being booted on a BIOS based system but also on a uEFI system.

Hear me out.

First of all, since I would be configuring everything myself, I would have the control - and obviously while the drive is still in this system, it would have to be able to boot from GRUB2 / another non-uEFI boot manager. However, when I upgrade (and the time is approaching very soon), I'm obviously going to move to a uEFI-based system. Now, I know that other discs like System Rescue CD and even Windows 10 (aka WinX) are able to boot onto both BIOS and uEFI. I have a Macrium Reflect bootable USB flash drive that does just that - able to boot on all three of my machines in order to make full images of the respective drives.

Second of all, when I upgrade my system, it will likely be mobo, CPU and RAM only - carrying over all other hardware until I decide later what else I want to upgrade (or unless I get a boatload of cash influx that I can use to start from scratch).

Based upon those two pieces of information, my thinking is that if I were to use genkernel to make a default fall-back kernel that can boot basically anything, I should, in fact, be able to set it up with GRUB2 to boot (as a fallback), but already have the partition structure set up for BIOS booting (with the tiny bit of free space at the beginning) as well as have the required /efi/boot/Gentoo/{genkernel}x64.efi files set up so that I can boot into the new system using uEFI without having to start all over from scratch.

Obviously, that space at the beginning of the drive will be sitting there doing absolutely nothing (or, I could leave it set up so that if something breaks on uEFI I have a secondary layer of fallback, using GRUB2, right?) when I move to a uEFI-based system, but I'm seriously not gonna complain about a missing 2 MB at the beginning of a 960 GB SSD. And since I am incorporating LVM into my design (I have, at various times, used a single block of space for everything / and under, separated /home out, an even had a multiple partition layout separating a few sets of directories into their own partitions, so, right now, using LVM is gonna allow me to move stuff around as I see fit / if I so desire, as I experiment and play and learn), I seriously don't want to set this machine up now only to have to start all over from scratch again when I build the new system.

The beauty of this would be mostly in that I could save myself tons of compile time, even if the new hardware will be 100 times faster than what I have now (likely an order of magnitude higher than that). But, with the genkernel .efi as the fallback, and GRUB2 as fallback to the fallback, I should, in theory, be able to plug this drive into the new system and fire it up and have a native CLI system to work with, with the majority of my configuration already working the way it should work so I can recompile a kernel for the new machine and its hardware.

You thoughts? In addition to the space at the beginning for GRUB2 to use, would I be better off making both a regular boot partition (as in the handbook) as well as an ESP (so I could mount /boot to the boot partition and /boot/EFI to the ESP)?

Caveat: I realize that I'm coming back to this after a long hiatus, and for all intents and purposes I'm a Gentoo n00b (look at my previous posts if you think otherwise :P ), but I cannot really see a problem with this theory - so please, if I'm being stupid, or just need a 'boot to the head', feel free - but I'd love the rationale behind why I'm off base, please.

After all, I'm here to learn, and am dedicating as much free time this summer as I can to learning my way around these machines and having Gentoo on them. Permanently.
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desultory wrote:
If you want to retain credibility as a functional adult; when you are told that you are acting boorishly, the correct response is to consider that possibility and act accordingly to correct that behavior.


Amen.


Last edited by johngalt on Mon Jul 02, 2018 2:27 am; edited 1 time in total
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eccerr0r
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PostPosted: Mon Jul 02, 2018 12:05 am    Post subject: Reply with quote

Since EFI can read MBR partition tables just fine, you can save a lot of headache and just use an MBR partition table, make an ESP on MBR, and install Grub to that partition. Technically you can install both MBR and EFI grub to that partition though I'm not sure if the Gentoo toolkit supports that directly.

Come to think of it I'm not sure if grub can be install MBR on an GPT partitioned disk, though perhaps it should be possible by using the usual "waste" space that should still be there in the protective MBR sector. But that would be a good question to find an answer to...
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johngalt
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PostPosted: Mon Jul 02, 2018 12:16 am    Post subject: Reply with quote

Sounds like I am going ot experiment then. :)
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desultory wrote:
If you want to retain credibility as a functional adult; when you are told that you are acting boorishly, the correct response is to consider that possibility and act accordingly to correct that behavior.


Amen.
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bunder
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PostPosted: Mon Jul 02, 2018 12:35 am    Post subject: Reply with quote

GPT and EFI booting is the future, I don't know why anyone would stick with MBR partitioning anymore except for MBR+BIOS compatibility.

Also GPT doesn't limit you to 4 primary partitions, they're just partitions.
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Ant P.
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PostPosted: Mon Jul 02, 2018 1:44 am    Post subject: Reply with quote

BIOS can boot from GPT disks fine too. I've recently switched to that, with a protective MBR so LILO can install to it.
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johngalt
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PostPosted: Mon Jul 02, 2018 2:27 am    Post subject: Reply with quote

Guess it won't be all that much experimentation then. Lol.

Thanks all. I'm gonna mark this solved for now.
_________________
desultory wrote:
If you want to retain credibility as a functional adult; when you are told that you are acting boorishly, the correct response is to consider that possibility and act accordingly to correct that behavior.


Amen.
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