Script to easily reset symbolic links for vmlinuz and initrd in the /boot directory on Linux

kernel_symlink_changer.sh

#!/bin/bash

usage() {
  echo "Usage: $0 [--apply]"
  echo "Default is dry-run mode. Use --apply to actually update symlinks."
  exit 1
}

if [ "$EUID" -ne 0 ]; then
  echo "You must run this script as root."
  exit 1
fi

# Dry-run as default
apply_changes=0

if [ "$1" == "--apply" ]; then
  apply_changes=1
elif [ "$1" != "" ]; then
  usage
fi

echo "Current symlink values:"
echo "  vmlinuz -> $(readlink -f /boot/vmlinuz)"
echo "  vmlinuz.old -> $(readlink -f /boot/vmlinuz.old)"
echo "  initrd.img -> $(readlink -f /boot/initrd.img)"
echo "  initrd.img.old -> $(readlink -f /boot/initrd.img.old)"
echo ""

# Fetch kernel lists
kernels=($(ls /boot/vmlinuz-* | xargs -n 1 basename))
echo "Available kernels:"
for i in "${!kernels[@]}"; do
  echo "$i) ${kernels[$i]}"
done

# Choose a default kernel
echo "Select the default kernel (current 'vmlinuz' symlink):"
read default_kernel_index

# Choose an old kernel
echo "Select the old kernel (current 'vmlinuz.old' symlink):"
read old_kernel_index

default_kernel="${kernels[$default_kernel_index]}"
default_initrd="initrd.img-${default_kernel#vmlinuz-}"

old_kernel="${kernels[$old_kernel_index]}"
old_initrd="initrd.img-${old_kernel#vmlinuz-}"

# Results
echo ""
echo "Selected default kernel: $default_kernel"
echo "Selected old kernel: $old_kernel"
echo ""
echo "Default kernel related files:"
echo "  vmlinuz -> /boot/$default_kernel"
echo "  initrd.img -> /boot/$default_initrd"
echo ""
echo "Old kernel related files:"
echo "  vmlinuz.old -> /boot/$old_kernel"
echo "  initrd.img.old -> /boot/$old_initrd"

# Apply
if [ $apply_changes -eq 1 ]; then
  echo "Applying changes..."
  sudo ln -sf "/boot/$default_kernel" /boot/vmlinuz
  sudo ln -sf "/boot/$default_initrd" /boot/initrd.img

  sudo ln -sf "/boot/$old_kernel" /boot/vmlinuz.old
  sudo ln -sf "/boot/$old_initrd" /boot/initrd.img.old

  echo "Symlinks updated successfully."
else
  echo ""
  echo "Dry-run mode: No changes made. Use --apply to update symlinks."
fi