How do I enable auto-login in Mint 18?

It seems there isn't a GUI setting for auto-login, except during initial installation.

Bahamut already pointed to the right solution. When look at the file: /etc/X11/default-display-manager, it points to the lightdm.

Then for Mint 18.2 (Cinnamon), the correct config file for lightdm is: /etc/lightdm/lightdm.conf.

The contents of the file could contain multiple settings:

  • Where USERNAME is your username, that should be auto-logged-in.
  • autologin-enable=true - this line was added for Linux MATE 18.3 64bit, but not tested for 18.2 Cinnamon. Remove it if necessary...

PS: Even it's too late to help the OP, it could be of help for other people. Let me know if someone can't get it working.

I have been looking for the same answer for Mint 19. I found the following and hope that the answer helps others.

Menu-Preferences-System Settings-Login Window--Users Tab-Username---Enter username

Save and reboot

Linux Mint 18.3 Cinnamon:

I did not have that /etc/lightdm/lightdm.conf at all. Instead, I appended code suggested by "Minister" here:

sudoedit /etc/lightdm/lightdm.conf.d/70-linuxmint.conf

and it works.