将 ubuntu 14.04 升级到 16.04 后，似乎可以与 gnome 配合使用，但我找不到安装或激活 unity 7 的方法。（现在与 lightdm 配合使用）您能帮忙吗？谢谢！
damien@earth:~$ sudo apt-get install --reinstall ubuntu-desktop
[sudo] password for damien:
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 to resolve the situation:
The following packages have unmet dependencies:
ubuntu-desktop : Depends: checkbox-gui but it is not going to be installed
Recommends: unity-webapps-common but it is not going to be installed
E: Unable to correct problems, you have held broken packages.