What is the correct procedure to replace MDM with LightDM on Linux Mint?

Question

OS: Linux Mint 18.3 Cinnamon 64-bit.

I almost got a heart attack, after reboot preceding this; in an important VM:

sudo apt-get install lightdm

... I chose LightDM as the default DM ...

sudo apt-get purge mdm

I underestimated it as after reboot the LightDM failed to start. What's more I could not get to Virtual Console, there was just an underscore blinking. After yet another reboot, the same behavior.

I fixed that in a while over SSH by purging LightDM and installing MDM back.

What is the correct procedure to replace MDM with LightDM on Linux Mint?

Solution 1

Following the official statement:

sudo apt-get install slick-greeter lightdm lightdm-settings apparmor

Did not yet get me to the result.

I had to create a file:

/etc/lightdm/lightdm.conf

with contents:

[Seat:*]
allow-guest=false

Solution 2

I believe this can be done with dpkg-reconfigure:

$ sudo dpkg-reconfigure lightdm

or

$ sudo dpkg-reconfigure mdm

http://manpages.ubuntu.com/manpages/trusty/man8/dpkg-reconfigure.8.html