原文地址：http://askubuntu.com/questions/360598/13-10-black-borders-black-terminal

I've just upgraded to Ubuntu 16.04 and I'm seeing a strange behaviour. All windows I open have a black, boxy border, including popups, as you can see in the provided image. (The black box in the bottom right is a terminal, which fails to display any text. However, I can enter commands and they execute.) I followed the steps in this post: How do I reset my Unity configuration? to reset Unity using the unity-tweak-tool. Although helpful, that did not fix the issue. I'm thinking this may be a graphics card driver issue.

Screenshot from 2017-01-01 18-31-27.png

solutions are as follows:

Removing the system-compositor-testing PPA

Should you have been using the system-compositor-testing PPA you will have to remove the PPA and it's content from your system prior to installing XMir from archive.

$> sudo apt-get update
$> sudo apt-get install ppa-purge
$> sudo ppa-purge ppa:mir-team/system-compositor-testing
$> sudo rm /etc/apt/preferences.d/50-pin-mir.pref

Then, follow "Installing from Archive".

Installing from Archive

Prior to landing Mir and related packages in the Ubuntu archive, we offered XMir via the system-compositor-testing ppa (ppa:mir-team/system-compositor-testing). As of August 9, 2013 XMir can be installed directly from archive via

$> sudo apt-get update
$> sudo apt-get dist-upgrade
$> sudo apt-get install unity-system-compositor
$> sudo apt-get install ubuntu-desktop-mir
$> sudo restart lightdm

Verifying that unity-system-compositor is running

You can check in 3 ways whether unity-system-compositor is running:

$> ps aux | grep unity-system-compositor
$> grep -i xmir /var/log/Xorg.0.log
$> ls -l /var/log/lightdm/unity-system-compositor.log

Removing unity-system-compositor

Temporarily

If you want to temporarily switch back to using X.org on your system, run following commands:
$> sudo vi /usr/share/lightdm/lightdm.conf.d/10-unity-system-compositor.conf

and add a comment to the second line:
[SeatDefaults]
#type=unity;xlocal

and restart lightdm
$> sudo restart lightdm

If you want to enable XMir back again, you simply remove the comment:
[SeatDefaults]
type=unity;xlocal

and restart lightdm
$> sudo restart lightdm

Permanently

In order to remove unity-system-compositor permanently from your system, run following command:

$> sudo apt-get remove unity-system-compositor
$> sudo restart lightdm

I choosed the "permanently", and the problem was finally solved.