安装过程出错：

sudo apt-get install openssh-server

输出如下错误：

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:
openssh-server : Depends: openssh-client (= 1:6.6p1-2ubuntu1)
E: Unable to correct problems, you have held broken packages.

google了一下，直接安装相应的版本就行: 

sudo apt-get install openssh-client=1:6.6p1-2ubuntu1