With gdm3, I was able to remove the last connected users from the list by removing the file '/var/log/ConsoleKit/history'

With lightdm, the last users appears even when :

• removing /var/log/ConsoleKit/history
• removing /var/lib/lightdm/.cache/unity-greeter/state

Where does lightdm store this list ?

Edit: It seems like it's using the content from the last command. Then purging the content of the file /var/log/wtmp is sufficient to remove any previously connected user from the list :

# > /var/log/wtmp

But, after doing this, I have the unwanted side effect that users loging in via lightdm doesn't appears at all in this list.

I must say that I'm in a enterprise network environment using NIS.

Edit2: Well, it seems that lightdm uses wtmp to display recent network users list, but does not update it. So, lightdm will show a network user only if it logged in in another fashion (ssh, login), like I did on this computer before. cf:

• https://bugs.launchpad.net/lightdm/+bug/871070
• http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=648604

Edit3: I just added the following line to the file /etc/pam.d/lightdm To force lightdm to store users in wtmp :

session optional        pam_lastlog.so silent