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turekpolski

Member

From: Poland

Registered: 2011-05-11

Posts: 28

UEFI dual-boot without ESP (msdos partition table)

Hi!
So I upgraded my computer a while ago, but yesterday I had to install Windows 8 alongside my ArchLinux.

And as I arrived at the point of installing GRUB, I stambled across a weird problem, which I don't understand. Every article about installing GRUB2 on UEFI systems and about dual-booting with Win8 treats about ESP (used as $esp in every code cited). I couldn't find any partitions suiting the description so I ran the command # parted /dev/sdX print command and this is what I've got.

root@ubuntu:/home/ubuntu# parted /dev/sda print
Model: ATA M4-CT128M4SSD1 (scsi)
Disk /dev/sda: 128GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type     File system  Flags
 1      1049kB  52.9GB  52.9GB  primary  ext4
 2      52.9GB  53.2GB  367MB   primary  ntfs         boot
 3      53.2GB  128GB   74.8GB  primary  ntfs

root@ubuntu:/home/ubuntu# parted /dev/sdb print
Model: ATA ST3500412AS (scsi)
Disk /dev/sdb: 500GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start  End    Size   Type     File system  Flags
 2      106MB  500GB  500GB  primary  ntfs

root@ubuntu:/home/ubuntu# parted /dev/sdc print
Model: ATA SAMSUNG HM250JI (scsi)
Disk /dev/sdc: 250GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End    Size   Type     File system  Flags
 1      1049kB  250GB  250GB  primary  ext4         boot

root@ubuntu:/home/ubuntu# parted /dev/sdd print
Model: Kingston DataTraveler SE9 (scsi)
Disk /dev/sdd: 15.6GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type     File system  Flags
 1      1049kB  15.6GB  15.6GB  primary  fat32        boot, lba

/dev/sda is my prime SDD, which stores Win8 and Archlinux.

Is this allright? I don't think so. It's neither GPT nor MBR. If I wanted to create one I will loose all my data (right?) and since I've used this for a while now (Win7 + ArchLinux booting from grub-legacy) I'd like to ask you if there is any possibility of walking around this? How can I get back to Dual-Booting but with Win8 now?

I'm running LiveUSB Ubuntu now tryig to fix this with help of arch-chroot.

Cheers!

Last edited by turekpolski (2014-02-24 17:16:19)

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Registered Linux User #511180

WonderWoofy

Member

From: Los Gatos, CA

Registered: 2012-05-19

Posts: 8,414

Re: UEFI dual-boot without ESP (msdos partition table)

msdos is the technically correct term for what most refer to as MBR partitioning.  The MBR is really the first 446bytes of the disk which a bios bootloader reads and boots from, while the msdos partition table is the remaining portion of the first sector that holds the partition information.

In theory, UEFI should be able to use msdos/MBR or GPT partitioning, though firmwares are still a bit buggy in the regard so it isn't always the case.  But if you are going to use UEFI, you have no choice but to have an EFI System Partition.  It is where the bootloaders or boot managers are stored and read from.

Luccianus

Member

Registered: 2013-08-24

Posts: 6

Re: UEFI dual-boot without ESP (msdos partition table)

If I understand correctly, you've installed Windows 8 and now you can't boot to Arch.
If that's it, you'll have to reinstall GRUB; as WonderWoofy says you're using a MBR-schema.

Given that, check out the wiki for intructions on how to install GRUB2.
I think your best choice is just using the regular MBR bootloader and your current ext4 partition (/dev/sda1) to hold GRUB info under /boot; it's the easiest way given your current setup, as windows is using BIOS-type loader since it only uses UEFI if you install it on a GPT partitioned disk.

Last edited by Luccianus (2014-02-24 23:29:31)

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Push my Arch through the roof!

srs5694

Member

From: Woonsocket, RI

Registered: 2012-11-06

Posts: 719

Website

Re: UEFI dual-boot without ESP (msdos partition table)

My suspicion is that you were never booting in EFI mode. I say this because none of your disks currently uses GPT or has an EFI System Partition (ESP). At a minimum, most EFIs require a FAT partition (normally an ESP) to hold boot loaders, and you don't have such a partition. Thus, unless you've accidentally deleted your ESP, and perhaps converted a disk from GPT to MBR, there's no way you could be booting in EFI mode.

Most modern computers ship with EFI firmware that also supports BIOS-mode booting via a subsystem called the Compatibility Support Module (CSM). This feature is sometimes activated via a firmware option called "legacy booting" or something similar. My suspicion is that this is what you've been using to boot all along. If I'm right, then you have nothing more to worry about that you would with any other OS installation on a regular BIOS-based computer.