How to disabling direct root login

Inorder to disable direct root login on a linux server, you need to do the following thing:

1. vi /etc/ssh/sshd_config in that file make 
Permitrootlogin no then save it

2. Restart sshd service

/etc/init.d/sshd restart

3. Now create a new user and set password for that user.

4. Add that user to the wheel group

vi /etc/groups // add that user to the group of wheel

5. Now logon to the server using the username and password and then do 
su - and provide the root password

Inorder to work this properly you should have the following permission settings

chmod 4755 /bin/su
chmod 1700 /etc/passwd
chmod 1700 /etc/shadow
chmod 1755 /etc/groups

If there is anything wrong with this permission, you may get permission denied or incorrect password errors.