Changing the default desktop on Ubuntu 16.0414 Dec 2017
In my office at university, I have a desktop machine managed by the IT department, that runs a customised version of Ubuntu 16.04. I have sudo and can install whatever packages I like, but not necessarily without causing problems with the customisations made by IT.
A while back I decided to install i3 instead of using the default desktop, Unity. This worked nicely for a while, and I eventually decided to switch back to Unity. I uninstalled i3 and the other packages I used alongside it. Then I tried to log into my user account on the lightdm login screen, and was greeted by a scary message, saying ‘Failed to execute login command’.
Uh-oh. It seems like the system was able to change my default desktop to i3 when I installed it, but not change it back when I removed it.
After much googling, I found several potential solutions to this:
ubuntuas the user’s session
[SeatDefaults] user-session=ubuntu ...
Run the following commands:
sudo dpkg-reconfigure ubuntu-session sudo dpkg-reconfigure ubuntu-desktop sudo apt install --reinstall ubuntu-session ubuntu-desktop
I did all of this, and still got the error. Those commands may have been necessary, I don’t know. What I do know is that after editing
/var/lib/AccountsService/users/my-username to say
XSession=ubuntu, I was able to log in again properly.