OpenSSH Server

OpenSSH Server
Introduction
This section of the Ubuntu Server Guide introduces a powerful collection of tools for the remote control of networked computers and transfer of data between networked computers, called OpenSSH. You will also learn about some of the configuration settings possible with the OpenSSH server application and how to change them on your Ubuntu system.
OpenSSH is a freely available version of the Secure Shell (SSH) protocol family of tools for remotely controlling a computer or transferring files between computers. Traditional tools used to accomplish these functions, such as telnet or rcp, are insecure and transmit the user’s password in cleartext when used. OpenSSH provides a server daemon and client tools to facilitate secure, encrypted remote control and file transfer operations, effectively replacing the legacy tools.
The OpenSSH server component, sshd, listens continuously for client connections from any of the client tools. When a connection request occurs, sshd sets up the correct connection depending on the type of client tool connecting. For example, if the remote computer is connecting with the ssh client application, the OpenSSH server sets up a remote control session after authentication. If a remote user connects to an OpenSSH server with scp, the OpenSSH server daemon initiates a secure copy of files between the server and client after authentication. OpenSSH can use many authentication methods, including plain password, public key, and Kerberos tickets.
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.
via OpenSSH Server.