我是新手，所以如果我写下的信息不够，请告诉我还需要添加什么。我正在尝试使用 xserver 创建虚拟显示器并启动 X 以使用 Unity 进行机器学习。这是我收到的错误消息：
ubuntu@ip-172-31-1-5:~$ sudo apt-get install xserver-xorg
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:
xserver-xorg : Depends: xserver-xorg-core (>= 2:1.17.2-2) but it is not going to be installed
Depends: xserver-xorg-input-all but it is not going to be installed or
xorg-driver-input
Recommends: xserver-xorg-video-all but it is not going to be installed
E: Unable to correct problems, you have held broken packages.