F21: can I have multiple X logins on the console?

edit

Yeah, what you're talking about is a multiseat configuration, and it's awesome. Systemd makes this possible in Fedora 21. I outline the general procedure on my blog and include a link to a detailed instruction set from Fedora 17 which is still applicable. Said general procedure is as follows:

1) Identify the seats currently defined for your system (probably just seat0).

loginctl list-seats

2) List the devices currently attached to the seats (simple if it’s just seat0)

loginctl seat-status seat0

3) Identify the devices you would like to repurpose for the new seat (seat1, in this example).

loginctl seat-status

4) Attach the devices to seat1.

loginctl attach seat0 /sys/devices/device_path_here [attach as many as are necessary for your purposes]

5) Observe success and rejoice.

The general prerequisites are sufficient hardware - you'll need two graphics adapters so that one can be assigned to each seat, and obviously you'll need two monitors, keyboards, and mice at a minimum. You can basically assign any device connected to your system to either seat, however, so you can even provide independent sound cards or other PCI/USB devices for each seat.

You can do something like xinit gnome-session -- :3 vt7 if you don't want to use GDM to switch sessions - although, GDM is probably doing more than simply launching gnome-session, so switching users with GDM is probably still a better approach.