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 what
FreeBSD displays are devices being detected. You can look through the boot messages again
by viewing /var/run/dmesg.boot.
For example, acd0 is the first IDE CDROM drive, while kbd0 represents the keyboard.
Most of these devices in a UNIX® operating system
must be accessed through special files called device nodes, which are located in the /dev directory.
When adding a new device to your system, or compiling in support for additional
devices, you may need to create one or more device nodes for the new devices.
On systems without DEVFS (this concerns all FreeBSD
versions before 5.0), device nodes are created using the MAKEDEV(8) script as
shown below:
# cd /dev
# sh MAKEDEV ad1
This example would make the proper device nodes for the second IDE drive when
installed.
The device file system, or DEVFS, provides access to
kernel's device namespace in the global file system namespace. Instead of having to
create and modify device nodes, DEVFS maintains this
particular file system for you.
See the
devfs(5) manual
page for more information.
DEVFS is used by default in FreeBSD 5.0 and above.
