unity - How do I change the default session for when using auto-logins?

When autologon is active, lightdm will start the Unity 3D session, not the 2D (or any other shell that I want to auto-login to).

Is there a way to start the shell I want automatically (autologon)?

Anyway, if autologon is disabled, the last used session is launched, and that's fine. I just want to choose which is default with autologon.

The list of sessions is described in the directory /usr/share/xsessions.

Some of the more common session names are as follows:

• For unity-2d the session file is called ubuntu-2d.desktop


• For gnome-classic the session file is called gnome-classic.desktop



• For gnome-classic (no effects) aka gnome-fallback the session file is called gnome-fallback.desktop


• For unity-3d the session file is called ubuntu.desktop


• For Lubuntu the session file is called Lubuntu.desktop


• For LXDE the session file is called LXDE.desktop

Thus, if you change the light-dm configuration file to "ubuntu-2d" this will default the session to Unity-2D

i.e.

sudo nano /etc/lightdm/lightdm.conf

change the line

user-session=ubuntu

to

user-session=ubuntu-2d

Note - if you don't have a lightdm.conf file then for a autologin use the following values for this file:

[SeatDefaults]
greeter-session=unity-greeter
user-session=ubuntu-2d
autologin-user=myusername
autologin-user-timeout=0

Another possibility is to run:

sudo /usr/lib/lightdm/lightdm-set-defaults -s 

E.g.:

sudo /usr/lib/lightdm/lightdm-set-defaults -s ubuntu-2d

This will also create the lightdm.conf file if it wasn't already present.