Lights out management

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Lights-out management (LOM) is the ability for a system administrator to monitor and manage servers by remote control regardless of whether the machine is powered on. A complete LOM system consists of a hardware component called the LOM module and a program that facilitates the continuous monitoring of variables such as microprocessor temperature and utilization. The program also allows for such remote operations as rebooting, shutdown, troubleshooting, alarm setting, fan-speed control, and operating system reinstallation.

Servicing and managing computer servers in a remote data center can require the physical presence of a system administrator. For example, the loading or removal of media, or direct interaction with the server through a console and keyboard. Such access requirements depend on a system administrator being co-located with the data center, an additional business expense.

A single LOM system can be used with more than one server without the need for on-site staff at any of the server locations. Communication between the controller and the remote servers can be done through an independent dial-up connection. More commonly nowadays, the LOM modules are connected by serial links to a separate management host; or the LOM module accepts telnet connections over an Ethernet connection. Either way, the LOM can then be remotely accessed over the Internet (through SSH to the management host, and/or a VPN). The LOM module keeps a record of all the operations (known as the event log), allowing the administrator to instantly check any or all of several hundred systems.

When using serial console servers care should be taken not to send any unsolicitated BREAK over the line (especially with Sun hardware, and also Linux if SysRq is enabled) as it can put the machine in "lom mode" otherwise.

An example of a LOM system is Sun's Advanced Lights Out Management (ALOM), which comes standard on newer Sun servers (SunFire V210/240/250/440, Netra 240/440.) Sun had a similar older product called LOM on their Netras, and also Remote System Control (RSC) on Sun VSP servers. Another example is Apple Computer's Xserve, serving LOM through the Ethernet network interface.