How to make a 301 in htaccess?

Question

Apache HTTP Server

Good afternoon!
The crux of the matter is that there are 2 domains site.ru and sub.site.ru so that when site.ru is requested, index.html opens and the entire main project opens on sub.site.ru, in other words, the main site moves to the sub domain and on the domain there will be a one-pager, how to implement this?

Answer 1

you translate the site,
you create a one-pager, what's wrong with that?
You create the second site you transfer the folder there.
On the old lie down 1 file.

Answer 2

when accessing the site.ru domain, the redirect should be to sub.site.ru