GRUB: restoring dual boot with Windows and installing a theme

After updating the kernel or GRUB, it’s common for Windows to disappear from the boot list. os-prober fixes it — but it needs some extra configuration to work.

Restoring Windows in GRUB

1. Enable os-prober

GRUB disabled os-prober by default in recent versions. Edit the configuration:

sudo nano /etc/default/grub

Add or change this line:

GRUB_DISABLE_OS_PROBER="false"

2. Mount the Windows partition (if necessary)

os-prober needs to see the NTFS partition mounted. If it isn’t mounted, do that first — you’ll need ntfs-3g:

sudo ntfs-3g /dev/nvme0n1p4 /mnt/win

Replace /dev/nvme0n1p4 with the correct partition. Use lsblk to identify which one belongs to Windows.

3. Run os-prober and regenerate GRUB

sudo os-prober
sudo grub-mkconfig -o /boot/grub/grub.cfg

os-prober detects the installed operating systems. grub-mkconfig regenerates the boot configuration file. After that, reboot and Windows should appear.

Manjaro note: on Manjaro there is the alias sudo update-grub which does the same thing as grub-mkconfig. On other distros, use the full command.

---

Installing the CyberRe theme

CyberRe is a cyberpunk theme for the GRUB boot screen. It looks great.

cd ~/Downloads
tar -xvf "Grub2-theme CyberRe 1.0.0.tar.gz"
cd "CyberRe 1.0.0"
sudo ./install.sh

The install script takes care of copying the files to the right place and updating GRUB. Reboot to see the result.