pg_ctl start
psql -c "create extension sslinfo;"


[postgres@centos7 ~]$ psql -c "\dx"
                    List of installed extensions
  Name   | Version |   Schema   |            Description             
---------+---------+------------+------------------------------------
 plpgsql | 1.0     | pg_catalog | PL/pgSQL procedural language
 sslinfo | 1.2     | public     | information about SSL certificates
(2 rows)