Server Operating System

A server operating system (Server OS) is a type of operating system that is designed to be installed and used on a server computer. It is an advanced version of an operating system, having features and capabilities required within a client-server architecture or similar enterprise computing environment. Some of the key features of a server operating system include:

• Ability to access the server both in GUI and command-level interface
• Execute all or most processes from OS commands
• Advanced-level hardware, software and network configuration services
• Install/deploy business applications and/or web applications
• Provides central interface to manage users, implement security and other administrative processes
• Manages and monitors client computers and/or operating systems

Most Popular Server Operating Systems
Popular server operating systems include Windows Server, Mac OS X Server, and variants of Linux such as Red Hat Enterprise Linux (RHEL) and SUSE Linux Enterprise Server. According to SpiceWorks, this list is the most deployed on-premises server operating systems (August 2016):

• Windows Server 2003
• Windows Server 2008
• Windows Server 2012
• Linux (excluding RHEL)
• Windows Server 2000
• Red Hat Enterprise Linus (RHEL)
• Mac OS X Server

Selecting a Server Operating System
There are many factors that should be taken into consideration in the selection of a server operating system. They include determining the amount of money one can afford to spend, the hardware requirements of the system, the applications that are included or "bundled" into the software, the power of the hardware and the system, security, scalability, administrative tools available and options to install third-party programs. Consideration of administrative tools and knowledge of how to use them also is important because a server operating system does not tend to be nearly as user-friendly as systems for non-commercial, single-user purposes are.

If the number of requests that client computers will be making of the server is very high, a very powerful server that can run on hardware with a very large storage capacity and multiple processors usually is needed to prevent downtime. Other hardware considerations are dictated by the specific server operating system of choice. Stability also is of extreme importance; if a web server hosting a commercial website breaks down, a company's sales could plummet and affect profits. Consideration of the availability of crucial applications that can run under the server operating system also is very important because if what is needed is not included, there will be the need to install third-party programs to satisfy computing needs such as the handling of company emails.

Common applications for Server Operating Systems

• File and printer sharing: File sharing involves setting up a common storage point for a company's documents - a network drive, as it were. Print sharing allows multiple computers to use a single printer. Windows 95, 98 and ME do have file and print sharing, but are not recommended for use as server OSes.
• Application services (including databases): a server OS's ability to run the applications you need is obviously crucial. Servers function as crucial database stores and shared environments for collaborative applications (such as networked MYOB or Quicken).
• Web site services: A hypertext transfer protocol (HTTP) server is included with many server OSes, either via an integrated application, or other HTTP applications such as the Apache open source server. Some OSes also come with more advanced features, such as database integration (so you can dynamically build Web pages based on information in a database), personalisation and scripting. The world's most popular HTTP server application, Apache, comes with just about every version of Unix and also runs on Windows. Microsoft provides Internet Information Server (IIS) for Windows platforms.
• E-mail, groupware and messaging: A central e-mail server allows you to forward and receive e-mails to and from your business, as well as control individual e-mail accounts based on a domain. Groupware applications, such as Lotus Notes, Microsoft Exchange or Novell GroupWise, provide email as well as much more sophisticated collaboration. These applications can include shared calendars, document version management, group forums, database/messaging integration, instant messaging and whiteboard sharing. Open source mail systems such as SendMail and Exim are also popular.
• Terminal services: Allow a client to run a productivity application on a server, while seeing the visual results of the application on their screen. For instance, a client ('terminal') could be running Microsoft Word on the server from their desktop. The server does all the processing work, and just transmits the graphical changes to the terminal, while taking the user's input (mouse movements and key strokes) and sending them to the server. This model allows a company to use clients that don't have a lot of processing power (and enforces the storage of documents on the server, rather than on local hard drives). A server with a lot of memory and a fast processor is needed if it's going to be running productivity applications for the whole office. Nearly every current server OS can do this via Windows Terminal Server, Citrix MetaFrame or the X Window System (which is used by Novell and just about every Unix variant).
• Caching: Speeding up network access (usually Internet access) by storing previously downloaded files in a cache - kind of like the way an Internet browser keeps a cache of the Web pages you have visited so it doesn't have to download the files all over again. Examples of caching server applications include Novell BorderManager, Microsoft Internet Security and Acceleration Server, Inktomi Traffic Server and Squid.