See the up-to-date post at http://www.snekul.com/wordpress/?p=400.
In Ubuntu 11.10 and above, Ubuntu has a guest session enabled by default on all computers, even on an upgrade from a release without the guest session. This is part of the new display manager added in the Ubuntu 11.10 release called lightDM. In some environments, a guest account may present an unacceptable risk. Starting in Ubuntu 12.10, an option for “Remote Login” is available in addition to the guest session. This too may represent an unacceptable risk in some environments. While I’m personally not too concerned with having an option to connect to remote workstations and servers at the login screen, utilizing the feature does require giving up some information to Canonical and require setting up a Ubuntu One account.
To disable the guest session and/or remote logon in Ubuntu 12.10 (Quantal Quetzal):
- Open a terminal window.
- Type “sudo nano /etc/lightdm/lightdm.conf”
- Type in your sudo password.
- Add the following in a new line at the end of the file if you want to disable the guest session: allow-guest=false
- Add the following in a new line at the end of the file if you want to disable the remote login option: greeter-show-remote-login=false
- If you choose to disable both, your lightdm.conf file should probably look like this:
- Hit CTRL-X to exit nano.
- Hit Y to save the file.
- Hit Enter to accept the original filename and overwrite the file.
- On the terminal, type “sudo restart lightdm” to restart the display manager. Doing so will require you to log in again and may close running apps, so save your work before doing so.
- The guest session and/or remote logon options should now be disabled.