Linux Devices - Part IV

Linux Devices - Part IV

We jumped into another GnomeCORE series last week. This time around, we’re taking a few days to look into the mysterious /dev directory on Linux systems. /dev contains the “device files” that communicate with the hardware on your system. We decided that these files aren’t really files at all, though they have many of the attributes of files. In fact, they’re abstractions of the hardware - representations of devices that make it possible for the kernel to communicate with the hardware. Today, we’re continuing this look into the /dev directory.

/mixer: The /dev/mixer directory exists to communicate with the Open Sound System (OSS), an essential element of communicating with many sound cards. My SoundBlaster PCI-512 (a budget SoundBlaster Live!), for example, utilizes OSS for all the normal SoundBlaster tweaks. This is an essential part of your sound subsystem if your card is capable of using OSS.

/null: What do you do if you want to send a file to nowhere, to a permanent void where it will never be recovered? You send it /dev/null and that’s that. This is a device file that’s even less of a device file than the others. /dev/null is, in effect, a black hole where to which files can be permanently banished. In the real world, /dev/null has some very useful applications. I, for example, use this black hole in my .procmailrc file, exiling known spam messages without a trace. While the concept of /dev/null sounds a bit odd, you’ll find more interesting uses for it as you progress along in your Linux use.

/psaux: /dev/psaux is the device file for PS/2 mice in Linux. This ties in nicely to our discussion of XF86Config, underway in the GnomeTWEAK section. Along with configuration lines for protocol, buttons and other mouse elements, XF86Config contains a line for the mouse device. If your mouse is a PS/2 mouse, it’s likely that this is the device file providing communication with the kernel.

Sound, mice and nothing. Each requires it’s own communicating file, a /dev file in Linux.

Tomorrow, we’ll look at parallel devices.