page_title: Server (computing)
section_title: Operating systems
hierarchical_section_title: Server (computing) / Operating systems
caption_attribution_description: English: Cobalt Qube 3 Español: Vista frontal de un Cobalt Qube 3
context_page_description: In computing, a server is a piece of computer hardware or software that provides functionality for other programs or devices, called "clients". This architecture is called the client–server model. Servers can provide various functionalities, often called "services", such as sharing data or resources among multiple clients, or performing computation for a client. A single server can serve multiple clients, and a single client can use multiple servers. A client process may run on the same device or may connect over a network to a server on a different device. Typical servers are database servers, file servers, mail servers, print servers, web servers, game servers, and application servers.
  Client–server systems are today most frequently implemented by the request–response model: a client sends a request to the server, which performs some action and sends a response back to the client, typically with a result or acknowledgment. Designating a computer as "server-class hardware" implies that it is specialized for running servers on it.
context_section_description: On the Internet the dominant operating systems among servers are UNIX-like open-source distributions, such as those based on Linux and FreeBSD, with Windows Server also having a significant share. Proprietary operating systems such as z/OS and macOS Server are also deployed, but in much smaller numbers.
  Specialist server-oriented operating systems have traditionally had features such as:
  GUI not available or optional
  Ability to reconfigure and update both hardware and software to some extent without restart
  Advanced backup facilities to permit regular and frequent online backups of critical data,
  Transparent data transfer between different volumes or devices
  Flexible and advanced networking capabilities
  Automation capabilities such as daemons in UNIX and services in Windows
  Tight system security, with advanced user, resource, data, and memory protection.
  Advanced detection and alerting on conditions such as overheating, processor and disk failure.
  In practice, today many desktop and server operating systems share similar code bases, differing mostly in configuration.
caption: Sun's Cobalt Qube 3; a computer server appliance (2002); running Cobalt Linux (a customized version of Red Hat Linux, using the 2.2 Linux kernel), complete with the Apache web server.
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