Mini Shell

#!/usr/bin/bash

if ! [[ $KERNEL_INSTALL_MACHINE_ID ]]; then
    exit 0
fi

COMMAND="$1"
KERNEL_VERSION="$2"
BOOT_DIR_ABS="$3"

# If $BOOT_DIR_ABS exists, some other boot loader is active.
[[ -d "$BOOT_DIR_ABS" ]] && exit 0

run_hooks()
{
    local f
    local files="$1"
    for f in $files ; do
        [ -x "$f" ] || continue
        "$f" "$KERNEL_VERSION" "/boot/vmlinuz-$KERNEL_VERSION"
    done
}

case "$COMMAND" in
    add)
        run_hooks "/etc/kernel/postinst.d/*[^~] /etc/kernel/postinst.d/$KERNEL_VERSION/*[^~]"
        ;;
    remove)
        run_hooks "/etc/kernel/prerm.d/*[^~] /etc/kernel/prerm.d/$KERNEL_VERSION/*[^~]"
        ;;
    *)
        exit 0
esac