rewrite url with virtual host - apache

Question

I have very limited experience with system administration and I'm currently trying to re-route/write (which ever is the appropriate term) sub-domains to top level domains. For example, I have a domain called bar.com, and I've created a number of sub-domains such as foo.bar.com. I'd like foo.bar.com to resolve to foo.com which I also own. Foo.com has an A record that points to the IP address where foo.bar.com resides.
If it sounds like I'm not describing this correctly, it's because I'm still learning how this all works.
The following is the foo.bar.com virtual host file.
foo.conf:
<VirtualHost 127.0.0.1:81>
Define DOCUMENT_ROOT /PATH/TO/PUBLIC/APP
Define PHP_PORT 22844
Define PHP_PROXY_URL fcgi://127.0.0.1:${PHP_PORT}
ServerAdmin webmaster#
DocumentRoot ${DOCUMENT_ROOT}
ServerName server-foo
ServerAlias foo.bar.com
ServerAlias www.foo.bar.com
ErrorLog "/PATH/TO/error.log"
CustomLog "/PATH/TO/access.log" common
</VirtualHost>
My question is how would I modify this file to make it so that foo.bar.com resolves to foo.com.

Answer 1

It sounds like you're looking for a way to redirect within the virtual host.
If that's the case then, you should be able to use mod_rewrite within your virtual host to accomplish this.
RewriteEngine On
RewriteCond %{HTTP_HOST} ^foo\.bar\.com$ [NC]
RewriteRule ^(.*) http://foo.com/ [L,R]
This thread might help: https://serverfault.com/a/120507
Edit: To have foo.com be the primary URL, use something like the below.
<VirtualHost 127.0.0.1:81>
ServerName foo.bar.com
ServerAlias www.foo.bar.com
Redirect "/" "http://foo.com/"
</VirtualHost>
<VirtualHost 127.0.0.1:81>
Define DOCUMENT_ROOT /PATH TO CURRENT FOO.BAR.COM/
[your other settings]
ServerName foo.com
</VirtualHost>