I recently documented how I installed Ruby Enterprise and nginx on Mac OS X. Here we see how to make subdomains work on your local development machine using nginx. These instructions should be relevant for most unix based systems.

Why use subdomains. On shared hosts like webfaction it is more efficient to serve images, downloads, etc from a nginx server rather than run them through your web application, like rails, sinatra, etc.

First modify you hosts file, adding in all the subdomains you need.

$ vim /etc/hosts     localhost     downloads.localhost

Then modify the nginx.config file, making it listen for the new subdomains.

http { 
   server {
      listen       80;
      server_name  localhost;
      passenger_enabled on;
      root /Users/Shared/Code/Amaras-Site/public;   # <--- be sure to point to 'public'!

   server {
      listen 80;
      server_name downloads.localhost;
      root  /Users/Shared/Code/Amaras-Site/Uploads; # <-- Not a Rack application just plain static files

NB: to find the location of your nginx.conf file:

$ find / -iname "nginx.conf"

Start or restart the nginx server

$ sudo ~/bin/nginx/sbin/nginx
$ sudo ~/bin/nginx/sbin/nginx -s reload

For portability in Sinatra applications I refer to subdomains using this method:

<% url = request.env["HTTP_HOST"] %>
<a href="http://downloads.<%=url%>/something">link to subdomain</a>