Just having my first play with 14.04 LTS (server), and I'm struggling!
The upgrade from 12.04 'almost' worked, but after struggling with intermittent hangs decided to back off and do a fresh install. There were numerous problems getting a bootable system, but finally achieved this with an absolutely clean install of a minimal system on totally fresh partitions.
My next step was to install lightdm/lightdm-gtk-greeter to give me a desktop manager. lightdm installed fine, but the greeter installation fails with
update-alternatives: error: alternative path /etc/lightdm/lightdm-gtk-greeter-ubuntu.conf doesn't exist'
Quite correct - it doesn't. I took a stab that this was purely a creation problem, so created an empty file, reran the installation, and it appears to work successfully. However, any attempts to start lightdm fail with
Seat: Stopping; failed to start a greeter
I haven't found anything in the greeter logs, and suspect the problem goes back to the greeter installation issues, and its not quite as simple as fudging the missing file. I've removed/reinstalled both lightdm and the greeter a number of times, but haven't got any further.
All versions should be the current stable versions - 1.10.3 for lightdm, and 1.8.5 for the greeter.
I've spent a bit more time today seeing if I could get to the bottom of this. I'm still suspicious that something hasn't installed correctly, but haven't a clue what.
I deinstalled the standard gtk greeter, and installed an alternative greeter (I happened to grab lightdm-webkit-greeter for no other reason that it was readily available). This installed fine, and on reboot I was presented with a standard login screen. That's a step forward, but it was impossible to login - it refused to authenticate.
Having a look at the lightdm log, there are some indications that authentication worked fine, but session creation was the culprit. There are log entries of the form;
- Authenticate result for user andrew: Success
- User andrew authorized
- Greeter requests session ubuntu
- Seat: Failed to find session configuration ubuntu
- Seat: Can't find session 'ubuntu'
Not sure if this is relevant at all, but I've been trying to understand exactly what config files should be present. /etc/lightdm exists, but is empty (I understand this was deprecated in 14.04, so makes sense). In /usr/share/lightdm/lightdm.conf.d there are the following config files;
40-lightdm-webkit-greeter.conf 50-greeter-wraper.conf 50-guest-wraper.conf 50-unity-greeter.conf 50-xserver-coand.conf
I won't pretend I understand how all these fit together, nor exactly what I should expect, but I assume the leading numbers give some order for processing these. A couple of entries in this forum have referred to a 50-ubuntu.conf, but I don't have one of those. Should there be one there (ie. is this the 'ubuntu' mentioned in the session creation error)? If so, this could indicate the problem is with the lightdm installation rather than the greeter?