Ubuntu 12.04 changed itself to xubuntu and stopped working

[Colin Law]

On 30 July 2015 at 11:11, Bret Busby <bret.busby at gmail.com> wrote:
> Hello.
>
> I have an Acer V3-772G laptop computer, which has an Intel i-7 4702MQ
> Haskell CPU/graphics controller and an nVidia GEForce GT-750M graphics
> thing.
>
> I have on the system, Debian 7, Debian 6, Ubuntu 14.04, and, what was
> Ubuntu 12.04, installed.
>
> After two yars of trying to get the computer working, I have found
> that, of those operating systems, only the two Ubuntu systems have the
> necessary drivers.
>
> To get the interrface that I wanted, I installed the mate desktop
> environment, along with a number of other desktop environments, and
> have been using the mate desktop environment as the preferred desktop
> environment, on both of the Ubuntu installations.
>
> In the last week, the Ubuntu 12.04 installation changed the boot
> splashscreen, to a blue one, and, after the blue splashscreen, the
> screens (I use an external monitor) go blank, and nothing else is
> displayed auntil I do a crash/reboot, using the power switch (holding
> it down until the system stops breathing).
>
> I have found that the blue screen displays "xubuntu", and in searching
> for that, I have found that xubuntu is an xfce version of Ubuntu.
>
> I had not wittingly switched the system from being Ubuntu, to xubuntu.
>
> In using the recovery mode booting, and getting to a root shell
> prompt, I tried to use apt-get remove xfce, in the hope that that
> would get rid of the switch from Ubuntu to xubuntu, and it reurned
> "xfce not found".

Did you have autologin enabled?  If so then first try disabling it so
that it should take you to a login screen where you can choose which
ui to use.  I have no longer got a 12.04 system to check, but have
have a look at /etc/lightdm/lightdm.conf if it exists.  In there you
should find a section [SeatDefaults] with a line
autologin-user=<your user name>
Make a backup of the file in case you mess it up and then in the
original delete the text after the = in that line and reboot, which
should take you to a login screen.

Colin