UEFI/MBR doubts on a fresh Arch in a dual boot system

virusso80 · 2023-11-03 10:46:32

Hi all,
after having some issue, after a windows10 heavy update (disk and MBR corruption) and having somehow managed the issues, I am going to give each OS its own home
My system storage is currently composed by:

# lsblk -l
Disk /dev/sda: 465.76 GiB, 500107862016 bytes, 976773168 sectors
Disk model: Samsung SSD 860
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x4a751bf7

Device     Boot     Start       End   Sectors  Size Id Type
/dev/sda1  *         2048 297763347 297761300  142G  7 HPFS/NTFS/exFAT
/dev/sda2       297764864 298893311   1128448  551M 27 Hidden NTFS WinRE
/dev/sda3       298895360 504969215 206073856 98.3G 83 Linux
/dev/sda4       504969216 976773119 471803904  225G 83 Linux


Disk /dev/sdb: 2.73 TiB, 3000592982016 bytes, 5860533168 sectors
Disk model: TOSHIBA HDWD130
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x3323932d

Device     Boot      Start        End    Sectors  Size Id Type
/dev/sdb1             2048 2965430271 2965428224  1.4T 83 Linux
/dev/sdb2       2965430272 5860532223 2895101952  1.3T 83 Linux


Disk /dev/nvme0n1: 953.87 GiB, 1024209543168 bytes, 2000409264 sectors
Disk model: KINGSTON SKC3000S1024G
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/sdc: 1.88 GiB, 2013265920 bytes, 3932160 sectors
Disk model: USB Flash Disk
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x6d0682af

Device     Boot   Start     End Sectors  Size Id Type
/dev/sdc1  *         64 1624063 1624000  793M  0 Empty
/dev/sdc2       1624064 1654783   30720   15M ef EFI (FAT-12/16/32)


Disk /dev/loop0: 685.52 MiB, 718819328 bytes, 1403944 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

(sdc is the usb device i connected with the live archiso)

I see the sda1, which is my SSD and contains both OSs.
I am going to install Arch on the nvme drive and then remove the linux partitions from sda.

questions:
1. here it says to verify the boot mode, and the command returns 64, which it is supposed to mean I have a UEFI boot mode.
however the output of fdisk shows that the disklabel type is "dos", which means it is booted in legacy mode.
Looking at the bios it seems the legacy is selected.
How do I interpret such contrasting information?

2. which partition scheme should i consider? UEFI or MBR? guide is a bit confusing...

3. can i convert everything to UEFI without reinstall windows 10? just asking because i know UEFI is more recent. Side note, the motherbord is an ASUS ROG Strix x470f, which supports UEFI. On't know why windows10 is booted in legacy mode.

4. as said i am going to install arch on the nvme (first time arch is alone). how do I choose partitions? how they interfer with the bootable partition currently used?

Thanks

Last edited by virusso80 (2023-11-03 10:50:30)

Scimmia · 2023-11-03 12:09:20

First thing to realize, MBR(dos) is a partition table. UEFI is a firmware type/interface. That should answer 1 and 2.

3. Not easily, no. It could be possible with converting to GPT, moving partitions around, creating a ESP, and repairing boot, but that's speculation on my part, and is probably worse than reinstalling.

4. You make the partitions, you format them, and you mount them. There is no interference unless you use one of the other partitions.

virusso80 · 2023-11-03 13:33:16

Scimmia wrote:

First thing to realize, MBR(dos) is a partition table. UEFI is a firmware type/interface. That should answer 1 and 2.
3. Not easily, no. It could be possible with converting to GPT, moving partitions around, creating a ESP, and repairing boot, but that's speculation on my part, and is probably worse than reinstalling.
4. You make the partitions, you format them, and you mount them. There is no interference unless you use one of the other partitions.

Hi, thanks for the answer.
Sorry, i intended GPT (not uEFI) in question 1...anyway thanks for noticing and clarifying
Question 1 is related to how to interpret the contrasting results...not clear how your clarification helps...

question 2 is then related to which scheme should i adopt...I guess MBR...

Scimmia · 2023-11-03 13:37:23

1. There is no contrasting results.

2. You're asking about the partition table? The vast majority of systems that will not have Windows on that disk should use GPT.

virusso80 · 2023-11-03 15:38:50

Scimmia wrote:

1. There is no contrasting results.
2. You're asking about the partition table? The vast majority of systems that will not have Windows on that disk should use GPT.

not clear what "that disk" is in my case.
mmm, what i do not understand is, you are suggesting I can set GPT on the new ssd only (which does not have win10), also if bios is in legacy and dual boot with windows (installed on the previous ssd), right?
I would really appreciate if you can elaborate your statements a bit more...:)
thanks

Lone_Wolf · 2023-11-04 16:05:27

Many modern (say 2018 or later) Uefi systems can boot fine from GPT or MBR (without needing legacy/CMS ) .

https://wiki.archlinux.org/title/Partit … PT_and_MBR should help to make the differences clear.

There's one hardware related difference : if one or more of your drives are bigger then 2 Terabyte , use GPT for those drives.

Don't know why windows10 is booted in legacy mode.

When windows 10 was released ( 2015 ?) uefi implementations were often buggy and unreliable. Bios implementations however were at the peak of their reliability.

I maintain a few windows 10 systems with pre-2018 hardware that are still running fine with bios / mbr installs .
(they can't run windows 11 and will probably have to be replaced in about 2 years) .

Arch Linux

#1 2023-11-03 10:46:32

UEFI/MBR doubts on a fresh Arch in a dual boot system

#2 2023-11-03 12:09:20

Re: UEFI/MBR doubts on a fresh Arch in a dual boot system

#3 2023-11-03 13:33:16

Re: UEFI/MBR doubts on a fresh Arch in a dual boot system

#4 2023-11-03 13:37:23

Re: UEFI/MBR doubts on a fresh Arch in a dual boot system

#5 2023-11-03 15:38:50

Re: UEFI/MBR doubts on a fresh Arch in a dual boot system

#6 2023-11-04 16:05:27

Re: UEFI/MBR doubts on a fresh Arch in a dual boot system

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