10-B.2.4: Server Roles in Linux (continued)

SSH Services

Secure Shell (SSH) is a cryptographic network protocol for operating network services securely over an unsecured network. Typical applications include remote command-line, login, and remote command execution, but any network service can be secured with SSH.

SSH provides a secure channel over an unsecured network by using a client–server architecture, connecting an SSH client application with an SSH server. The protocol specification distinguishes between two major versions, referred to as SSH-1 and SSH-2. The standard TCP port for SSH is 22. SSH is generally used to access Unix-like operating systems, but it can also be used on Microsoft Windows. Windows 10 uses OpenSSH as its default SSH client and SSH server.

There are several clients that allow users to connect to an SSH server. Linux systems come with a command line, as well as a GUI based clients. For Windows the most popular is Putty, which does not come with Windows but is easily downloaded.

Virtualization/Container Services

Virtualization

Virtualization is a technique of how to separate a service from the underlying physical delivery of that service. It is the process of creating a virtual version of something like computer hardware. It was initially developed during the mainframe era. It involves using specialized software to create a virtual or software-created version of a computing resource rather than the actual version of the same resource. With the help of virtualization, multiple operating systems and applications can run on the same machine and its hardware at the same time, increasing the utilization and flexibility of hardware.

Virtual Machines

In computing, a virtual machine (VM) is an emulation of a computer system. Virtual machines are based on computer architectures and provide functionality of a physical computer. Their implementations may involve specialized hardware, software, or a combination.

A virtual machine is a file, called an image, that mimics an actual computer. In other words, it creates a computer within a computer. It runs within an app like any other program, giving the end user the same experience on a virtual machine as they would have on the guest operating system itself. The host machine is protected from the guest system, meaning that the software inside a virtual machine can’t access the host computer itself, other than some of the hardware devices if so configured.

VPN Services

A virtual private network (VPN) extends a private network across a public network and enables users to send and receive data across shared or public networks as if their computing devices were directly connected to the private network. Applications running across a VPN may therefore benefit from the functionality, security, and management of the private network. Encryption is a common, although not an inherent, part of a VPN connection.

VPN technology was developed to provide access to corporate applications and resources to remote or mobile users, and to branch offices. For security, the private network connection may be established using an encrypted layered tunneling protocol, and users may be required to pass various authentication methods to gain access to the VPN. In other applications, Internet users may secure their connections with a VPN to circumvent geo-blocking and censorship or to connect to proxy servers to protect personal identity and location to stay anonymous on the Internet. Some websites, however, block access to known IP addresses used by VPNs to prevent the circumvention of their geo-restrictions, and many VPN providers have been developing strategies to get around these blockades.

A VPN is created by establishing a virtual point-to-point connection through the use of dedicated circuits or with tunneling protocols over existing networks. A VPN available from the public Internet can provide some of the benefits of a wide area network (WAN). From a user perspective, the resources available within the private network can be accessed remotely.

Web Services

The term Web service (WS) refers to either a service offered by an electronic device to another electronic device, communicating with each other via the World Wide Web, or it is a server running on a computer device. The server listens for requests at a particular port over a network, serves web documents (HTML, JSON, XML, images), and creates web applications services, which serve in solving specific domain problems over the Web (WWW, Internet, HTTP)

There is a lot that falls under the heading of "web services." For the most part it communicates via one of the two protocols: 1) HTTP, which uses TCP port 80; or 2) HTTPS, secure HTTP, which runs on TCP port 443.

Adapted from:
"Secure Shell Protocol" by Multiple Contributors, Wikipedia is licensed under CC BY-SA 3.0
"Virtualization In Cloud Computing and Types" by Namrata Bisht, Geeks for Geeks is licensed under CC BY-SA 4.0
"Dynamic Host Configuration Protocol" by Multiple Contributors, Wikipedia is licensed under CC BY-SA 3.0