Our bathroom floor had linoleum over the flooring and we decided to replace it with a (12 inch) glazed tile floor. The floor underneath is very sturdy and flat. A 1/4 inch underlayment will go under the tiles.

Is it necessary to put down cement to install the underlayment, before nailing it down? We do not intend to take up the linoleum as it is impossible to pry up. As far as we can tell, there are only a couple of places where cement might be necessary to level out the underlayment. Thanks for any advise.