Reload nginx config

First make your changes to nginx.conf.

Then run the following command to test the new configuration:

# nginx -t -c /etc/nginx/nginx.conf
2007/10/18 20:55:07 [info] 3125#0: the configuration file /etc/nginx/nginx.conf syntax is ok
2007/10/18 20:55:07 [info] 3125#0: the configuration file /etc/nginx/nginx.conf was tested successfully
Next, look for the process id of the master nginx process:

# ps -ef|grep nginx
root 1911 1 0 18:00 ? 00:00:00 nginx: master process /usr/sbin/nginx
www-data 1912 1911 0 18:00 ? 00:00:00 nginx: worker process
Lastly, tell nginx to reload the configuration and restart the worker processes:

# kill -HUP 1911

taken from:
http://snippets.aktagon.com/snippets/93-Change-nginx-configuration-on-the-fly