Arch Linux

NumeroSMG

Member

Registered: 2016-08-23

Posts: 25

[SOLVED] Dualboot - Unable to restore Grub after installing Win...

I freed up 150GB of space from the partition which had Arch installed, and installed Windows 10 there.
It works and boots fine, but now I am unable to boot into my Archlinux - if I specify I want to boot into it in my bios boot order - it loads GRUB with an error "unkown filesystem. Entering resuce mode... grub rescue> ".

I tried restoring Grub from my Arch CD but with no change.
Here's my fdisk -l output:

Disk /dev/sda: 931.5 GiB, 1000204886016 bytes, 1953525168 sectors
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: gpt
Disk identifier: 9890EC49-A24C-42FC-A1D6-5E0C364B3D6C

Device          Start        End    Sectors   Size Type
/dev/sda1          34       2047       2014  1007K BIOS boot
/dev/sda2        2048    4196351    4194304     2G Linux swap
/dev/sda3     4196352 1645531135 1641334784 782.7G Linux filesystem
/dev/sda4  1645531136 1646452735     921600   450M Windows recovery environment
/dev/sda5  1646452736 1646657535     204800   100M EFI System
/dev/sda6  1646657536 1646690303      32768    16M Microsoft reserved
/dev/sda7  1646690304 1953523711  306833408 146.3G Microsoft basic data

Partition 1 does not start on physical sector boundary.

Disk /dev/loop0: 408.1 MiB, 427905024 bytes, 835752 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

The steps I tried:
mounting sda3 and arch-chrooting in, grub-installing in /dev/sda1 (and /dev/sda3), then generating grub.cfg

I am also confused about the whole BIOS/UEFI deal... If I remember correctly, when I installed Arch on this machine, after removing Windows 10 - it said "Legacy BIOS" in System information, thus I proceeded to install Arch and Grub in BIOS method, but if I now check the same thing on my newly installed Win10 - it says UEFI.

Last edited by NumeroSMG (2017-12-18 15:39:47)

Morn

Member

Registered: 2012-09-02

Posts: 886

Re: [SOLVED] Dualboot - Unable to restore Grub after installing Win...

I think Windows 10 would not have created an EFI system partition if the PC was actually BIOS-based.

Personally I have ditched GRUB after getting a similar error message (and getting dropped into rescue mode) on my new system and have installed rEFInd instead. So maybe give rEFInd a try? The only trouble with rEFInd was that kernel auto detection fails if multiple kernels (e.g. linux and linux-lts) are installed, so make sure you only have a single kernel installed.

lo1

Member

Registered: 2017-09-25

Posts: 584

Re: [SOLVED] Dualboot - Unable to restore Grub after installing Win...

Sector size (logical/physical): 512 bytes / 4096 bytes
...
Device          Start        End    Sectors   Size Type
/dev/sda1          34       2047       2014  1007K BIOS boot
...
Partition 1 does not start on physical sector boundary.

First of all, if you decide to ignore this, it may be harmless but remember that you have a non-aligned partition when/if you experience I/O issues.

Disklabel type: gpt
/dev/sda1          34       2047       2014  1007K BIOS boot
/dev/sda5  1646452736 1646657535     204800   100M EFI System

Then, your disk is gpt, which *may* run just fine with a legacy boot partition, but it will be better you stick with UEFI this time.
IMHO, this disk partitioning will cause you some troubles (best practice would be to have an EFI partition at the start of your disk, even if this is not strictly necessary).

Now to the part you don't want to hear: I'm afraid Windows 10 converted your disk from "dos" to "gpt" and messed up your disk, and thus you may need to start over with installing arch.
Maybe there are some ways to recover your Arch installation without data loss, but I don't really have a clue, never done that before.

Probably I'm wrong, so before taking it for granted, post every step you take when (re)installing GRUB (your live CD has EFI compatibility, right?)

Last edited by lo1 (2017-12-18 14:37:33)

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NumeroSMG

Member

Registered: 2016-08-23

Posts: 25

Re: [SOLVED] Dualboot - Unable to restore Grub after installing Win...

I have managed to restore it, turns out I was reinstalling Grub in an incorrect way. Here are the steps that brought me to the result I was after:
From the Arch CD:

mount /dev/sda3 /mnt
arch-chroot /mnt
grub-install --target=-386-pc /dev/sda
grub-mkconfig -o /boot/grub/grub.cfg
exit
umount -R /mnt
reboot

(Prior to that I was trying to grub-install it to /dev/sda1 and to /dev/sda3, which is why I was unsuccesful)

Now I am able to to access Grub menu and start-up Arch from there. It doesn't have an entry for Windows, which is only a slight inconvenience for me at this point as I am rather happy it works at last.
Also from what I can tell from reading Wiki: https://wiki.archlinux.org/index.php/GRUB#Dual-booting

Windows installed in UEFI-GPT Mode menu entry

This mode determines where the Windows bootloader resides and chain-loads it after Grub when the menu entry is selected. The main task here is finding the EFI partition and running the bootloader from it.

Note: This menuentry will work only in UEFI boot mode and only if the Windows bitness matches the UEFI bitness. It will not work in BIOS installed GRUB. See Dual boot with Windows#Windows UEFI vs BIOS limitations and Dual boot with Windows#Bootloader UEFI vs BIOS limitations for more info.

So I will restrain from messing with it any more at this point, I can access both Windows and Arch, and that makes the problem solved for me.
Thank you for your help.

Last edited by NumeroSMG (2017-12-18 15:41:08)

nl6720

The Evil Wiki Admin

Registered: 2016-07-02

Posts: 718

Re: [SOLVED] Dualboot - Unable to restore Grub after installing Win...

The only trouble with rEFInd was that kernel auto detection fails if multiple kernels (e.g. linux and linux-lts) are installed, so make sure you only have a single kernel installed.

Take a look at "extra_kernel_version_strings" in refind.conf
Although it will still not detect fallback initramfs or intel microcode. But it's always possible to use manual boot stanzas.

Morn

Member

Registered: 2012-09-02

Posts: 886

Re: [SOLVED] Dualboot - Unable to restore Grub after installing Win...

The only trouble with rEFInd was that kernel auto detection fails if multiple kernels (e.g. linux and linux-lts) are installed, so make sure you only have a single kernel installed.

Take a look at "extra_kernel_version_strings" in refind.conf
Although it will still not detect fallback initramfs or intel microcode. But it's always possible to use manual boot stanzas.

I think what happened was that it loaded the LTS kernel with the regular initramfs. There was an error message about missing modules and the partition could not be found. At first I thought the UUID was wrong and only later I asked myself, why does it say "linux-lts" in the rEFInd menu instead of just linux? A classic case of a misleading error message, as there was nothing wrong with the Linux partition itself. But apart from that rEFInd is really nice.