http://d.hatena.ne.jp/lettas0726/20110723/1311386896

redmine.conf

upstream unicorn {
  server unix:/tmp/unicorn.sock;
}

server {
  listen 80;
  server_name example.com;
  root /var/www/redmine/public;
  error_log /var/www/redmine/log/error.log;
  location / {
    if (-f $request_filename) { break; }
    proxy_set_header X-Real-IP  $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $http_host;
    proxy_pass http://unicorn;
  }
}