Failed to start session with LXDE on Ubuntu Server

**fabius85** · March 10th, 2024

I'm having trouble starting LXDE on Ubuntu Server.

I installed Ubuntu Server 22.04.4 LTS on a VM, logged in and run:

Code:

sudo apt update && sudo apt upgrade

Then installed LXDE:

Code:

sudo apt install lxde

After that i rebooted and when entering the password I got the error message: "Failed to start session" and nothing else happened.
If installing xinit package i can succesfully start LXDE from the command line with startx command.
But this doesn't solve the problem cause if i try to login from LightDM, i always get that message.

The only wordaround i found to make this work is to install lightdm-gtk-greeter package, reboot, login from the gtk greeter at least once.
After that i can even remove lightdm-gtk-greeter package and purge it, and the default ubuntu greeter for LightDM will work as expected and no longer give "Failed to start session" error.

I'm wondering why that error occurs and if there's a proper way to fix it without the lightdm-gtk-greeter workaround.

PS: installing lubuntu-desktop package is not an option as i dont need any of the stuff that it comes with. I just need a minimal graphical interface.

**MAFoElffen** · March 10th, 2024

When you install a minimal LXDE or LXQT desktop with LightDM, it is installed without a default pointer to the user-session set in file /etc/lightdm/lightdm.conf.

When it only has one Desktop installed, it doesn't trigger the process to turn on and populate LightDM's Session Chooser, so you need to tell it which session to use. As you mentioned, if you installed something like ubuntu-desktop, it would trigger that process, because it has two session types (more than one), Ubuntu Xorg & Ubuntu Wayland, so would trigger that process to populate the Session Chooser.

Of course that would add unwanted fluff. Not what needs to happen with a minimal install goal.

If you open file /etc/lightdm/lightdm.conf, and look under the Section [SeatDefaults]... By default, on a clean minimal install, here is the default contents:

Code:

[SeatDefaults]
autologin-user=

To get around that error ("Failed To Start Session"), and get it to work, add this line to point a session:

Code:

user-session=lxde

Just one of those things that isn't well documented.

Of course, now that you have installed a desktop on a Server Eition, this thread is now more of a "Desktop" question, but no matters.

**fabius85** · March 10th, 2024

There was no /etc/lightdm/lightdm.conf file, so I created it and added the following content:

Code:

[SeatDefaults]
user-session=LXDE

rebooted and it worked!

I initially tried with user-session=lxde (lowercase) but i still got the "Failed to start session" error.
I think it's uppercase because there's a "LXDE.desktop" file inside "/usr/share/xsessions/" folder.

It works also this way:

Code: