Ubuntu 14.04 - You have held broken packages

Question

This is a very popular question, but bear with me as I have tried everything you are all about to suggest. So this is what I get:

sudo apt-get install ubuntu-desktop
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help resolve the situation:

The following packages have unmet dependencies:
 ubuntu-desktop : Depends: ubuntu-session but it is not going to be installed
                  Depends: unity-control-center but it is not going to be installed
                  Depends: unity-settings-daemon but it is not going to be installed
                  Recommends: xul-ext-webaccounts but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

So I try to install unity-control-center

Depends: unity-settings-daemon but it is not going to be installed

So I try to install unity-settings-daemon

Depends: gnome-settings-daemon-schemas (< 3.10) but 3.12.2-0ubuntu1~trusty2 is to be installed

The root problem appears to be that gnome-settings-daemon-schemas version 3.10 or less is needed, but it can't get it for some reason.

So you might be thinking try the following:

sudo apt-get update
sudo apt-get upgrade
sudo apt-get dist-upgrade
sudo apt-get clean
sudo apt-get autoclean
sudo dpkg --configure -a
sudo -f

I am logged into gnome, when I try to boot into lightgdm the system hangs right after something about printer spooling.

I currently have gdm, kdm and lightgdm.

I want my computer back to just gnome and ubuntu unity. Any thoughts? (A re-install is out of the question)

Solution

Unity is based on gnome. A lot of the unity packages (and ubuntu-desktop) packages depend on gnome packages.

So the problem here appears to be that the Gnome 3.12 ppa has been added.

gnome-settings-daemon-schemas

is part of Gnome. The packages you are trying to install (ubuntu-desktop) need version 3.10 from gnome, but it can't get to version 3.10, because of the ppa telling it to get it from the 3.12 repos.

If you want unity back, you need to install the previous version:

sudo apt-get install gnome-settings-daemon-schemas=3.8.6.1-0ubuntu11.2

but this will remove some because of dependencies - so gnome 3.12 will break...

The following packages will be REMOVED
  gdm gnome-control-center gnome-session gnome-settings-daemon gnome-shell
The following packages will be DOWNGRADED:
  gnome-settings-daemon-schemas

Comments

[Tim]

Yep, have the same problem myself. I have moved to gnome - try askubuntu.com/questions/452864/…

[user3379926]

@Tim None of that helps. I want unity back.

[Tim]

Have you added the gnome 3.12 ppa?

[HCarrasko]

it doesnt work.

[Tim]

What error message?

[HCarrasko]

the same error of the question, I run gnome-settings-daemon-schemas but the order does not exist

[Tim]

Don't know then, sorry...