A device is a term used mostly for hardware-related activities in a system, including disks, printers, graphics cards, and keyboards. When FreeBSD boots, the majority of the boot messages refer to devices being detected. A copy of the boot messages are saved to /var/run/dmesg.boot.
Each device has a device name and number. For example, acd0 is the first IDE CD-ROM drive, while kbd0 represents the keyboard.
Most devices in a FreeBSD must be accessed through special files called device nodes, which are located in /dev.
When adding a new device to your system, or compiling in support for additional devices, new device nodes must be created.
The device file system, DEVFS, provides access to the kernel's device namespace in the global file system namespace. Instead of having to manually create and modify device nodes, DEVFS automatically maintains this particular file system. Refer to devfs(5) for more information.