Be careful with this. Since you have to reboot with the new file, and there no way to test, it is easy to have a machine that doesn't have a usable console. Usually, a wrong mode won't prevent the machine from booting, so if you can log into your machine remotely, you can wait until it boots and change the file that way. If you can't log into your machine remotely, you'll have to boot off an alternative media (such as the CD).