How to create a Sub domain in Rackspace

hi all, i’m using a Rack Space server now i want to create a sub domain
for my rails app.can any one help me out i have Google it but did not
correct link which can help me.

Thanks in advance

What web server are you using? Nginx?

Em tera-feira, 26 de junho de 2012 09h43min30s UTC-2, honey ruby

it Nginx