错误提示：

ferris@UBT14LTS-VM:~$ sudo apt-get install openssh-server
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:
 libcogl15 : Depends: libegl1-mesa-drivers
 openssh-server : Depends: openssh-client (= <span style="color:#009900;">1:6.6p1-2ubuntu1</span>)
E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.

先安装openssh-server指定版本的openssh-client：

Ubuntu 14:

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

Ubuntu 18:

sudo apt-get install openssh-client=1:7.6p1-4

再安装openssh-server：

sudo apt-get install openssh-server