In each of my posts on setting up a local development environment on OS X, it's mentioned that you need to add your website's domain, even though it's local, in your /etc/hosts file. My preferred way to edit the hosts file on OS X is using Gas Mask. If you wanted to create the local virtual host projectx.dev, you would add the line 127.0.0.1 projectx.dev in /etc/hosts or with Gas Mask, and then use that same value in either ServerName in Apache or server_name in Nginx. This can be tedious for adding new sites. Luckily there's a way to set this up once and then never have to edit your hosts file again for adding new local virtual hosts.
The steps below will install dnsmasq from Homebrew, configure dnsmasq to return the IP address '127.0.0.1' for all requests to the fake top-level-domain ".dev," start dnsmasq on boot (don't worry, it's an extremely light-weight process), and configure OS X to use dnsmasq for queries ending in ".dev."
brew install dnsmasq mkdir -pv $(brew --prefix)/etc/ echo 'address=/.dev/127.0.0.1' > $(brew --prefix)/etc/dnsmasq.conf sudo cp -v $(brew --prefix dnsmasq)/homebrew.mxcl.dnsmasq.plist /Library/LaunchDaemons sudo launchctl load -w /Library/LaunchDaemons/homebrew.mxcl.dnsmasq.plist sudo mkdir -v /etc/resolver sudo bash -c 'echo "nameserver 127.0.0.1" > /etc/resolver/dev'
That's it! You can run scutil --dns to show all of your current resolvers, and you should see that all requests for a domain ending in .dev will go to the DNS server at 127.0.0.1:
resolver #9 domain : dev nameserver : 127.0.0.1
If you ping any domain that ends in .dev, you'll get the IP address 127.0.0.1 back as a result:
$ ping -c 1 thereisnowaythisisarealdomain.dev PING thereisnowaythisisarealdomain.dev (127.0.0.1): 56 data bytes 64 bytes from 127.0.0.1: icmp_seq=0 ttl=64 time=0.057 ms
Note that if you're using Mountain Lion you may need to reboot before the /etc/resolver settings take effect globally. I was able to get pings to work right away but Chrome would not resolve properly until I restarted.
Now you can set up a new virtual host with anydomain.dev, and it'll be available as soon as you reload Apache or Nginx! You could extend this by enabling Mass Virtual Hosting for Apache or similar with Nginx, though both require consistent layout of directories. Have fun configuring less stuff on your system!