SSH连接错误

用xshell客户端连接主机出现错误：

ssh 用户名@ip_address [port]

官方文档上的提示：

"Could not connect to ‘hostname‘ (port 22): Connection failed."

Check if the host machine is ready for connection and the port is reachable. If you are connecting to a SSH server, make sure that SSH daemon is running on the remote host.

于是sudo apt-get install openssh-server

出现如下错误：

解决方法：安装所有安全更新和重要更新

问题解决。