Secure Shell (SSH) is an extremely useful tool when administering a number Linux servers. For instance, in my home office environment I have server configured with Proxmox Virtual Environment on whch I host a number of Ubuntu 14.04 virtual servers, which I use for all my development, testing and DevOps environment. I will frequently need to access those machines to carry out some administration tasks or configuration. Being able to access them any terminal window on any of the workstations that I have scattered around my office and home, is a real convenience.
What is Secure Shell ?
Secure Shell, or rather more commonly referred to as SSH, enables the secure communication between networked computers enabling users to log-in to a remote machine and run commands and interact with the file system, as if you directly on the machine while using the Terminal Window on your machine.
SSH is not enabled on Ubuntu by default. A SSH command is available, on a server but it only the client module, which will enable a server to communicate externally with other servers, but no servers will be able to connect to it.
To enable SSH on a server or desktop can be done by installing openssh-server from the ubuntu repositories i.e. apt-get
After installing, you should be able to access the server as is, using SSH from the terminal using ssh username@host i.e
However, you may want to male some configuration changes to servers SSH configuration file to improve security. You can access the configuration file using any text editor.
After you have made your changes, you simply need to restart the service