How to make Lubuntu login automatically?

According to the Lubuntu documentation, https://help.ubuntu.com/community/Lubuntu/Boot_Install_Login#For_release_12.04_and_on_.28LightDM.29, You will need to create an /etc/lightdm/lightdm.conf with these contents: (do this as root)

[SeatDefaults]
autologin-user=<YOUR USER>
autologin-user-timeout=0
# Check https://bugs.launchpad.net/lightdm/+bug/854261 before setting a timeout
user-session=Lubuntu
greeter-session=lightdm-gtk-greeter

This solution worked for me. The link (at the bottom) is dead but I got a cached version.

$ sudo nano /etc/lightdm/lightdm.conf

Add the following lines replacing myusername with your user:

[Seat:*]
pam-service=lightdm
pam-autologin-service=lightdm-autologin
autologin-user=myusername
autologin-user-timeout=0

To check use:

$ /usr/sbin/lightdm --show-config

Source: http://www.neatlittleinsights.com/htdocs/lubuntu_16.04_autologin.html

Lubuntu uses LightDM for login, You need to modify the config file. You need to check, where are they:

/usr/sbin/lightdm --show-config

You will see the proper config files under the "Sources" paragraph.

Then you can edit the first one with root privileges (eg. for Ubuntu 17 this is):

sudo nano /usr/share/lightdm/lightdm.conf.d/20-lubuntu.conf

Add your username to the autologin-user line (or add the line if it is not defined). It will look like:

[Seat:*]
user-session=lubuntu
autologin-user=myusername
autologin-user-timeout=0

Save and check again with

/usr/sbin/lightdm --show-config