reexec: check root status

shopt -s nullglob

(( UID > 0 )) && { echo "You must be root" >&2; exit 1; }

type -P kexec >/dev/null || { echo "kexec is not in PATH" >&2; exit 1; }

[[ -r /boot ]] || { echo "Unable to read /boot" >&2; exit 1; }