How to remove subdomain from index

[zokiii]

I would like to remove subdomain from google's index.

Do I need to have different robots.txt for my subdomain ?

I put this robots.txt in my subfolder :
User-agent: *
Disallow: /

And it is reachable with subdomain.domain.com/robots.txt

I use different robots.txt for subdomain.

Is this ok ?

[jakomo]

Hello,
This is correct, but to help more add under each a href the tag rel="nofollow"...