A headless server is a computer without a monitor, keyboard, mouse, or other peripherals. Headless computers are normally controlled over the network. For example, picture the computers sitting on racks in data centers while powering websites. Those are headless servers.
What Does “Headless” Mean?
A “headless” computer system is just one without a local interface. There’s no monitor (“head”) plugged into it. There’s also no keyboard, mouse, touchscreen, or other local interface for controlling it.
These systems aren’t computers you sit down and use like a desktop computer. They don’t have a graphical interface set up. You access and administer them remotely—generally over a network. For example, you might control a headless server through a web-based control panel or via SSH, which gives you a secure command-line shell you can access over a network. You could even access a graphical desktop over the network with a solution like Remote Desktop or VNC.
You’ll see the term “headless” pop up in a variety of different contexts, but it always means the same thing. “Headless Linux” refers to a Linux system without a monitor and keyboard. A “headless Minecraft server” is a computer without a monitor and keyboard running a Minecraft server. You connect to the server over the network.
What’s the Point of a Headless Server?
Not every computer system needs a monitor, keyboard, and mouse. Many computers are servers designed for remote access. Data centers are full of “rack-mounted” computers, packing as much computing powers into as small a space as possible. They’ll save space, electricity, and money by not connecting each server computer to a separate monitor.
Headless systems aren’t just for data centers. For example, you might choose to host a media server on an old computer you have lying around, letting you stream media from any device on your local network. Once you have, you might decide that you can just remove the media server computer’s monitor, keyboard, and mouse—after all, you just access it over the network. You can keep your server PC in a closet somewhere and control it without sitting down in front of it. You now have a headless server.
These systems can be controlled and managed remotely without the peripherals getting in the way. If there is a reason you need a monitor and keyboard with a headless server—perhaps for troubleshooting a problem—you can always connect those peripherals when you need them.
For example, Gartner estimated Google had around 2.5 million servers in its data centers around the world back in July 2016. Those are largely going to be headless servers—Google doesn’t need 2.5 million monitors and keyboards, too.