Comment 40 for bug 870297

I've written a patch that updates utmp and uses pam_lastlog for wtmp. It seems
to work:

root@test-precise:~# w
 18:22:27 up 1:16, 2 users, load average: 2.44, 1.03, 0.68
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
root pts/0 remotehost 17:06 0.00s 3.40s 0.01s w
lotheac tty7 18:23 1:17m 1.07s 0.67s awesome

But, there's a problem: since the greeter session is started the same way as the
user session, we get unnecessary entries by the lightdm user when the login
screen is visible:

root@test-precise:~# who
root pts/0 2012-04-19 17:06 (this is an ssh session)
lightdm tty7 2012-04-19 18:05
root@test-precise:~# w
 18:06:50 up 1:00, 2 users, load average: 0.59, 0.41, 0.42
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
root pts/0 remotehost 17:06 0.00s 3.03s 0.01s w
lightdm tty7 18:05 1:00m 0.36s 0.01s /bin/sh /usr/lib/lightdm/lightdm-greeter-session /usr/sbin/lightdm-gtk-greeter
root@test-precise:~# last -n3
lightdm :0 Thu Apr 19 18:05 still logged in
lotheac :0 Thu Apr 19 17:56 - 18:05 (00:09)
lightdm :0 Thu Apr 19 17:56 - 17:56 (00:00)

wtmp begins Mon Apr 16 14:40:28 2012

I don't think greeter sessions should be handled identically to user sessions;
I'm not sure why it needs to go through the pam stack at all. Maybe someone
more familiar with lightdm can shed some light on this?

The attached patch isn't finished, since it introduces the issue described
above.