Linux superuser password settings and user __linux

First unlock root, set password for root user 

open terminal input: sudo passwd

        Password: <---Enter your current user's password 

        enter new UNIX Password: <--- New root password Retype new

        UNIX password: <---Repeat root password

         passwd: Password has been updated successfully

You can then switch to root

There are two ways for Su to switch to Superuser:
1.su root: Get the user's temporary permissions, the environment does not change
2.su-root: completely switch to root user