Console server

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A console server (also console access server or console management server or serial console server) is a device or service that provides access to the system console of a computing device via networking technologies.

Most commonly, a console server provides a number of serial ports, which are then connected to the serial ports of other equipment, such as servers, routers or switches. The consoles of the connected devices can then be accessed by connecting to the console server over a serial link such as a modem, or over a network with terminal emulator software such as telnet or ssh, allowing remote users to log in the various consoles without being physically nearby.

Dedicated console server appliances are available from a number of manufacturers in many configurations, with the number of serial ports ranging from one to 32 or more, with varying features provided by their embedded software.

Many users have created their own console servers using off-the-shelf commodity computer hardware, usually with multiport serial cards (such as those from Cyclades or Digi), typically running a slimmed-down Unix-like operating system such as Linux. Such "home-grown" console servers can be less expensive, especially if built from components that have been retired in upgrades, and allow greater flexibility by putting full control of the software driving the device in the hands of the administrator. This includes full access to and configurability of a wide array of security protocols and encryption standards, making it possible to create a console server that is more secure.

This increased flexibility comes at the cost of an increased workload on an administrator, however, requiring time and effort to set-up and maintain another computer, as opposed to console server appliances, which "just work" after minimal configuration. This greater administration burden can translate into a higher total cost of ownership than console server appliances, despite the potentially lower initial cost.

An alternative approach to a console server used in some cluster setups is to null-modem wire and daisy-chain consoles to otherwise unused serial ports on nodes with some other primary function.