Hello to everybody.

I try to add the sub-domain and describe it in configuration files of nginx.

I read a lot from internet resources about this issue and i got the next solution:
server {
listen 80;
server_name sub.sitename.com;
root /var/www/sitename.com/sub;
index index.html index.php;
}

What is wrong and what is need also?

Do i need to edit etc/hosts?

Thanks beforehand to all.