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#1 2017-01-07 17:19:21

mean_booty
Member
Registered: 2016-09-15
Posts: 26

[SOLVED] Attempting to dual-boot a MBR/BIOS Win7 with UEFI/GPT Arch

Let me start off my saying that I have done this before. At least, I think I have. I had an Arch Linux build on my old 2006 Seagate 200GB HDD. I upgraded to a WD Blue SSD 500GB. On my old drive, I had grub installed which was able to activate the windows bootloader or boot into Arch. My ARch was UEFI/GPT and my Windows is on a different drive and is MBR/BIOS. It wasn't hard to set up as Grub with OS-Prober recognized it.

My Windows is on sda. Sda1 is system reserved 100M and sda2 is the main files of size 111.7G.

My Arch installation is gpt.

    sdb1 = 25G "/"
    sdb2 = 430G "/home"
    sdb3 = 750M "/boot"
    sdb4 = 10G "swap"

My problem is that on my new SSD, I have installed another Arch build and grub refuses to recognize the windows bootmgr even with custom rules put in.

    menuentry "Windows 7"
        set root=(hd0,1)
        chainloader +1
        boot
    }

I have tried different variations of the above, but to no avail.



    if [ "${grub_platform}" == "pc" ]; then
      menuentry "Microsoft Windows Vista/7/8/8.1 BIOS-MBR" {
        insmod part_msdos
        insmod ntfs
        insmod search_fs_uuid
        insmod ntldr     
        search --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 69B235F6749E84CE
        ntldr /bootmgr
      }
    fi

The problem with the above from the wiki is that it assumes that Arch is also booting from BIOS.

I have also tried using rEFInd and I changed the scan parameters to scan both internal UEFI and internal BIOS systems. This causes it to find all of my data drives as well as my windows drive. The problem is that when I try to boot windows from there, the message comes up "Reboot and Select proper Boot device" like it can't find the windows boot manager.

Is there something I am missing? Am I out of luck trying to dual-boot these drives and will have to use my UEFI bios boot selector?

Last edited by mean_booty (2017-01-12 18:37:15)


MSI B450I Gaming Plus AC | Ryzen 3600X | 32 GB 3200MHz Micron-E | RX 5700XT Pulse

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#2 2017-01-12 18:36:35

mean_booty
Member
Registered: 2016-09-15
Posts: 26

Re: [SOLVED] Attempting to dual-boot a MBR/BIOS Win7 with UEFI/GPT Arch

After a lot of reading and some experimentation with different grub setups and partition schemes, I figured out that if I follow This old installation page it is actually what I did the first time.

To summarise:

Install grub-bios with pacman. I had already installed efibootmgr so I had to remove that and delete the /boot/grub and /boot/efi folders. This allowed me to install grub in /boot/grub with an i386-pc boot. I then used os-prober to probe sda and then made the grub config. It chainloaded windows bootmgr correctly now.

This essentially installs grub in BIOS mode even while using a GPT partition scheme. It is very easy unlike most GPT/BIOS boot tutorials. This is a good practice (to me) in case I do a windows update to 10 or past that instead of windows.

I am not sure if there is currently a way to completely dual boot a UEFI and a BIOS OS pairing. Maybe with a different motherboard than my GIGABYTE z87x-UD4H.

I will mark as solved.


MSI B450I Gaming Plus AC | Ryzen 3600X | 32 GB 3200MHz Micron-E | RX 5700XT Pulse

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