scripts/arch_post_update_update_boot.sh

#!/bin/sh
# arch_post_update_update_boot.sh
#
# In your /etc/profile, export the following variables
# LVM_VG_BOOT=vg0
# LVM_LG_BOOT_NAME=boot
# BOOT_DIR_SUFFIX=/archlinux
#
# Optional variables:
# PACMAN_BIN=/usr/bin/pacman # Alternative pacman binary (eg: aura)
# BOOT_SYMLINK=current (in good boot dir)

set -e

source /etc/profile

ask_overwrite() {
  echo "Existing destination folder ($ARCH_BOOT_DST_CURRENT_VERSION), do you want to overwrite? (y/n)";
  read OVERWRITE;
  test "$OVERWRITE" = "y" && return
  echo "Do not overwrite. Exitting gently..."
  exit 0;
}

PACMAN_BIN=${PACMAN_BIN:-/usr/bin/pacman}
BOOT_SYMLINK=${BOOT_SYMLINK:-current}

CURRENT_VERSION=`${PACMAN_BIN} -Qi linux \
  | sed -n '/^Version *:/p' \
  | grep -o '[^ ]*$'`
BOOT_BLK=/dev/$LVM_VG_BOOT/$LVM_LG_BOOT_NAME
BOOT_ORIG=/boot
TMP_BOOT_DST=`mktemp -d`

ARCH_BOOT_DST=$TMP_BOOT_DST/$BOOT_DIR_SUFFIX
ARCH_BOOT_DST_CURRENT_VERSION=$ARCH_BOOT_DST/$CURRENT_VERSION 
ARCH_INITRAMFS=initramfs-linux.img
ARCH_INITRAMFS_FALLBACK=initramfs-linux-fallback.img
ARCH_VMLINUZ=vmlinuz-linux

mount $BOOT_BLK $TMP_BOOT_DST;
test -d $ARCH_BOOT_DST_CURRENT_VERSION \
  && test `realpath $ARCH_BOOT_DST/$BOOT_SYMLINK` = $ARCH_BOOT_DST_CURRENT_VERSION \
  && echo "Linux version already up to date ($CURRENT_VERSION)" && exit 0;

mkdir $ARCH_BOOT_DST_CURRENT_VERSION || ask_overwrite;

(
    cd $BOOT_ORIG;
    # Copy the new kernel files to the real destination in boot fs
    cp -t $ARCH_BOOT_DST_CURRENT_VERSION $ARCH_INITRAMFS $ARCH_INITRAMFS_FALLBACK $ARCH_VMLINUZ;
)

(
    cd $ARCH_BOOT_DST;
    # Re-link the good version
    test -h $BOOT_SYMLINK && rm $BOOT_SYMLINK;
    ln -s $CURRENT_VERSION current;
)


echo "Linux version updated to $CURRENT_VERSION"
umount $TMP_BOOT_DST;
rmdir $TMP_BOOT_DST;
exit 0;