who nominates cabinet members and who are they confirmed by
Cabinet of the United States The heads of the executive departments and all other federal agency heads are nominated by the President and then presented to the Senate for confirmation or rejection by a simple majority (although before the use of the "nuclear option" during the 113th US Congress, they could have been blocked by filibuster, requiring cloture to be invoked by ​3⁄5 supermajority to further consideration). If approved, they receive their commission scroll, are sworn in and then begin their duties.
United States presidential line of succession The succession follows the order of vice president, Speaker of the House of Representatives, President pro tempore of the Senate, and then the heads of federal executive departments who form the Cabinet of the United States. The Cabinet currently has fifteen members, beginning with the Secretary of State, and followed by the rest in the order of their positions' creation. Those heads of department who are ineligible to act as president are also ineligible to succeed the president by succession, for example most commonly if they are not a natural-born U.S. citizen.