Install/Enable Open SSH in Ubuntu

Installation

Installation of the OpenSSH client and server applications is simple. To install the OpenSSH client applications on your Ubuntu system, use this command at a terminal 
prompt:sudo apt-get install openssh-client

To install the OpenSSH server application, and related support files, use this command at a terminal prompt:
sudo apt-get install openssh-server

The openssh-server package can also be selected to install during the Server Edition installation process.

Configuration

You may configure the default behavior of the OpenSSH server application, sshd, by editing the file /etc/ssh/sshd_config. For information about the configuration directives used in this file, you may view the appropriate manual page with the following command, issued at a terminal prompt:
man sshd_config

There are many directives in the sshd configuration file controlling such things as communication settings and authentication modes. The following are examples of configuration directives that can be changed by editing the /etc/ssh/sshd_config file.

sudo cp /etc/ssh/sshd_config /etc/ssh/sshd_config.original
sudo chmod a-w /etc/ssh/sshd_config.original