$ 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:
openssh-server : Depends: openssh-client (= 1:7.2p2-4)
Depends: openssh-sftp-server but it is not going to be installed
Recommends: ssh-import-id but it is not going to be installed
E: Unable to correct problems, you have held broken packages.
解决方法
给需要的源打钩，不需要的源不打钩。
关闭后$sudo apt-get update搞定。
发现一个好用scp，可视功能。