Try this. To disable autologin, just press Ctrl+Alt+T on your keyboard to open Terminal. When it opens, run the command below.
sudo leafpad /etc/lxdm/default.conf
In the fist few line, you will see something like autologin=username
change it to the original state of
# autologin=dgod
. Save the file, and then reboot your machine.
Also try to go to System Settings --> Users and Groups, click on change next to Password
Make sure that the box is unchecked next to Don't ask for password on login
Try to edit sudo leafpad /etc/lightdm/lightdm.conf
with these contents:
Remove or comment out the following lines
autologin-user=username
autologin-user-timeout=0
For 14.04 everything works. The /etc/lightdm/lightdm.conf
doesn't exist in 14.04, but the other ways work. See image below:
Best Answer
According to the Lubuntu Wiki https://help.ubuntu.com/community/Lubuntu/Boot_Install_Login#For_release_12.04_and_on_.28LightDM.29
you must
For release 12.04 and on (LightDM)
You will need to create an /etc/lightdm/lightdm.conf with these contents: (do this as root)
It appears that what you have tried and say does not work is similar but not the same as this solution.