Add update_grub.sh

Signed-off-by: Tommy <contact@tommytran.io>

update_grub.sh

@@ -0,0 +1,27 @@
+#!/bin/bash
+
+# Copyright (C) 2021-2024 Thien Tran
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License. You may obtain a copy of
+# the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations under
+# the License.
+
+# Install new grub version
+grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=GRUB --modules="normal test efi_gop efi_uga search echo linux all_video gfxmenu gfxterm_background gfxterm_menu gfxterm loadenv configfile gzio part_gpt cryptodisk luks gcry_rijndael gcry_sha256 btrfs" --disable-shim-lock
+
+# Disable root subvol pinning.
+## This is **extremely** important, as snapper expects to be able to set the default btrfs subvol.
+# shellcheck disable=SC2016
+sed -i 's/rootflags=subvol=${rootsubvol}//g' /mnt/etc/grub.d/10_linux
+# shellcheck disable=SC2016
+sed -i 's/rootflags=subvol=${rootsubvol}//g' /mnt/etc/grub.d/20_linux_xen
+
+# Generate grub config
+grub-mkconfig -o /boot/grub/grub.cfg