given $ x in mathbb {R ^ n} $ I now have the first derivative of the absolute value function

$$ frac {d | x |} {dx} = frac {x} {| x |}. $$

But what is the second derivation of it? I need it to calculate the second derivative for the function $ u: mathbb {R} ^ n rightarrow mathbb {R} $

$$ u (x) = | x | ^ alpha $$

With $ alpha> 0. $