Redirect a known folder on subdomain to main site for nginx

Question

I have several subdomain based sites in my CMS like:

a.site.com
b.site.com

All uploaded files are under the /upload directory like:

site.com/upload/2012/a.jpg

But URL's are generated like this: "/upload/2012/a.jpg". In this situation, the same image can be accessed at a.site.com/upload/2012/a.jpg URL and b.site.com/upload/2012/a.jpg URL.

How can I configure nginx to redirect all requests that point to /upload to site.com/upload. Example:

a.site.com/upload/2012/a.jpg => site.com/upload/2012/a.jpg

Answer 1

adding the following to the config for your subdomains should do the trick if you have a sepperate server block for *.site.com

location /upload/ {
  rewrite ^ http://site.com$request_uri permanent;
}

if you're catching both site.com and *.site.com in the same server block you need to add an extra if statement to that:

location /upload/ {
  if( $host != site.com ) {
    rewrite ^ http://site.com$request_uri permanent;
  }
  # if we get here it's the main site
  # directives for serving http://site.com/upload/ go here
}

Answer 2

Nginx not generate urls. It is a web server. It answer to requests like http://site.com/upload/2012/a.jpg.

So you can change relative links /upload/2012/a.jpg in you html code to absolute http://site.com/upload/2012/a.jpg and not change nginx config. Or change nginx config for subdomains and nginx will send same image for http://site.com/upload/2012/a.jpg and http://a.site.com/upload/2012/a.jpg and http://b.site.com/upload/2012/a.jpg requests.

If you prefer change config you have to create unificated config for all subdomains. Because

When searching for a virtual server by name, if name matches more than one of the specified variants, e.g. both wildcard name and regular expression match, the first matching variant will be chosen, in the following order of precedence

server {
    listen       80;
    server_name  *.site.com;

    location ^~ /upload {
         root   /real/path/to/upload/; 
         ...
    }

}

location directive manual