Switched to gdm from cde for my login screen on OpenSolaris. This is how you can do that (assuming you want to use GNOME and not using CDE.)
- Close all your applications.
- As superuser, do svcadm disable cde-login. You will immediately exit out of your session. You will be displayed a commandline login prompt.
- Login now and do svcadm enable gdm. It this one doesn’t work for some reason, you can always fall back by doing svcadm enable cde-login.