By  default,  only the user who installed the system is permitted to run sudo. To add more
       administrators, i. e. users who can run sudo, you have to add these  users  to  the  group
       'admin' by doing one of the following steps:

       * In a shell, do

           sudo adduser username admin

       * Use  the graphical "Users & Groups" program in the "System settings" menu to add the new
         user to the admin group.