How to list logged-in users on Scientific Linux (RHEL clone)?

Solution 1:

I believe in RHEL6 (before systemd anyhow) session management is tracked by consolekit.

Try ck-list-sessions and see if that shows you anything.

For completeness, on Fedora 16 and 17 this feature was deprecated in favour of systemd-logind which you can list sessions with using loginctl.