Changes to local hosts file lost

When staging websites locally, I edit my hosts file to point a given URL to localhost, so I can preview sites with the correct URL for link testing, etc.

To do so, I ru开发者_如何转开发n

sudo vi /etc/hosts

then edit my file and save with :wq.

This works fine until I reboot. As soon as I restart, my changes are lost.

However, only changes I've made that reference localhost (like 127.0.0.1 www.somesite.com) are wiped out. Changes I've made to point to staging servers (like 555.555.55.5 www.anothersite.com) remain.

What am I missing here?