Introduction

GRUB is highly configurable without third‑party tools. By editing a few files and generating the final config, you get predictable results that are easy to track in dotfiles.

Here’s my minimal, reproducible GRUB setup using only config files:

Customization Options

1) Essential Files to Edit

/etc/default/grub          # Main configuration
/etc/grub.d/00_header      # Header customization

2) Install Requirements

sudo pacman -S grub os-prober ttf-dejavu

The os-prober package detects other OSes like Windows. The ttf-dejavu package provides a clean monospace font for GRUB.

3) Configure /etc/default/grub

GRUB_TIMEOUT_STYLE=menu
GRUB_GFXMODE=1920x1080x32
GRUB_THEME="/boot/grub/themes/minimal/theme.txt"
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_DISABLE_OS_PROBER=false

4) Create a Minimal Theme

Create the directory and theme file:

# Create theme directory
sudo mkdir -p /boot/grub/themes/minimal

# Create theme.txt
sudo nano /boot/grub/themes/minimal/theme.txt

Example theme.txt:

desktop-color: "#000000"
title-color: "#EEEEEE"
message-color: "#AAAAAA"
message-bg-color: "#111111"
terminal-font: "DejaVu Sans Mono"

+ boot_menu {
    left = 30%
    top = 30%
    width = 40%
    height = 40%
    item_font = "DejaVu Sans Mono 14"
    item_height = 30
    item_padding = 5
    item_color = "#111111"
    selected_item_color = "#888888"
}

5) Generate a Font File

sudo grub-mkfont -s 18 -o /boot/grub/fonts/DejaVuSansMono18.pf2 \
/usr/share/fonts/TTF/DejaVuSansMono.ttf

6) Create a Custom Menu Entry

Add to 40_custom:

sudo nano /etc/grub.d/40_custom

Sample entry for Windows 11 (replace YOUR_WINDOWS_UUID with actual UUID):

#!/bin/sh
exec tail -n +3 $0

menuentry "Windows 11" {
    search --no-floppy --fs-uuid --set=root YOUR_WINDOWS_UUID
    chainloader (${root})/EFI/Microsoft/Boot/bootmgfw.efi
}

Find Partition UUIDs:

# For Windows EFI partition
sudo blkid /dev/nvme1n1p1

7) Generate the Final Config

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

# Verify entries
grep menuentry /boot/grub/grub.cfg

Troubleshooting: Emergency Shell Recovery

If you see “You are now being dropped into an emergency shell”, this means initramfs failed to mount your root filesystem. Fix it quickly by following these steps:

1. Identify Root Partition

# List available block devices
lsblk -f

# If lsblk isn't available:
# Try mounting likely candidates:
# NVMe drives: /dev/nvme0n1p2, /dev/nvme1n1p1
# SATA drives: /dev/sda2, /dev/sdb1

2. Mount Root Partition

# Mount your Linux root partition to /new_root
mount /dev/nvme0n1p2 /new_root

# If you have separate boot partition:
mount /dev/nvme0n1p1 /new_root/boot

3. Exit to Continue Boot

exit

4. Fix After Boot

# Verify root parameter in GRUB config
grep GRUB_CMDLINE_LINUX /etc/default/grub

# Should include root parameter like:
# GRUB_CMDLINE_LINUX="root=/dev/nvme0n1p2"

# Regenerate GRUB config
sudo grub-mkconfig -o /boot/grub/grub.cfg