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Ashen Chathuranga
Ashen Chathuranga

Posted on • Edited on

GRUB Configuration Guide for Dual Boot (Arch Linux + Windows)

#grub #arch #windows

This guide explains how to configure GRUB on Arch Linux for a dual-boot setup with Windows 10 or 11, ensuring that both operating systems appear in the GRUB menu.

✅ Prerequisites

  • A UEFI system with both Arch Linux and Windows installed.
  • EFI system partition (ESP) mounted at /boot/efi.
  • GRUB installed: 
  sudo pacman -S grub efibootmgr
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  • Required tools: 
  sudo pacman -S os-prober ntfs-3g
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⚙️ Step-by-Step Instructions

1. Edit GRUB Configuration

Edit the GRUB settings to enable OS detection and customize the menu.

sudo nano /etc/default/grub
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Recommended Settings: 

GRUB_TIMEOUT=5
GRUB_TIMEOUT_STYLE=menu
GRUB_CMDLINE_LINUX_DEFAULT="loglevel=3"
GRUB_DISABLE_OS_PROBER=false
GRUB_GFXMODE=auto
GRUB_GFXPAYLOAD_LINUX=keep
# Optional theme (install separately)
# GRUB_THEME="/usr/share/grub/themes/Vimix/theme.txt"
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💡 Explanation:

  • GRUB_TIMEOUT=5: Show GRUB menu for 5 seconds.
  • GRUB_TIMEOUT_STYLE=menu: Forces menu to display.
  • GRUB_DISABLE_OS_PROBER=false: Enables detection of other OSes like Windows.
  • loglevel=3: Reduces log noise during boot.
  • GFXMODE/PAYLOAD: Enables consistent graphical boot.

Save and exit the file:

  • Ctrl+O, Enter, then Ctrl+X.

2. Verify EFI Partition is Mounted

Ensure your EFI system partition is mounted at /boot/efi:

findmnt /boot/efi
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If not mounted, find the EFI partition (usually FAT32) and mount it:

sudo mount /dev/sdX1 /boot/efi
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Replace /dev/sdX1 with your actual EFI partition (check with lsblk or fdisk -l).

3. Detect Windows with os-prober

Check if os-prober detects Windows:

sudo os-prober
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You should see output like:

/dev/sdXY:Windows Boot Manager:Windows:chain
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If not:

  • Ensure the NTFS partition is accessible.
  • Check that Windows is not hibernated or BitLocker-locked.

4. Regenerate GRUB Configuration

After configuring everything, generate the GRUB config:

sudo grub-mkconfig -o /boot/grub/grub.cfg
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You should see messages like:

Found Windows Boot Manager on /dev/sdXY
Found Arch Linux on /dev/sdXZ
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5. (Optional) Reinstall GRUB

Only do this if GRUB doesn't load at boot or is corrupted.

sudo grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=GRUB
sudo grub-mkconfig -o /boot/grub/grub.cfg
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6. Reboot 

reboot
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You should now see the GRUB menu with options for:

  • Arch Linux
  • Windows Boot Manager
  • UEFI Firmware Settings

🛠 Troubleshooting

  • No Windows Entry in GRUB Menu:

    • Ensure GRUB_DISABLE_OS_PROBER=false is set.
    • Reinstall os-prober and ntfs-3g.
    • Run sudo os-prober manually and check output.
    • Reboot into Windows and disable Fast Startup.

  • Check Boot Mode (UEFI vs BIOS):

  [ -d /sys/firmware/efi ] && echo "UEFI mode" || echo "BIOS mode"
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  • Backup GRUB Settings: 
  sudo cp /etc/default/grub /etc/default/grub.bak
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  • Manually Edit Boot Parameters:

    • Press e at the GRUB menu to edit boot options for a session.

  • View Boot Logs:

  journalctl -b
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🎨 Optional: GRUB Theme

Install a GRUB theme for a visual boost:

yay -S grub-theme-vimix
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Then enable it in /etc/default/grub:

GRUB_THEME="/usr/share/grub/themes/Vimix/theme.txt"
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🧱 GPU Drivers (Optional)

Install appropriate GPU drivers to avoid graphical issues:

# NVIDIA
sudo pacman -S nvidia nvidia-utils

# AMD
sudo pacman -S mesa xf86-video-amdgpu

# Intel
sudo pacman -S mesa xf86-video-intel
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✅ Summary

Task Command
Install required tools sudo pacman -S grub os-prober ntfs-3g
Edit GRUB config sudo nano /etc/default/grub
Enable Windows detection GRUB_DISABLE_OS_PROBER=false
Mount EFI sudo mount /dev/sdX1 /boot/efi
Generate config sudo grub-mkconfig -o /boot/grub/grub.cfg
(Optional) Reinstall GRUB sudo grub-install ...
Reboot system reboot

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