3.10.5 Installing the Other Components

		4.7 Linux's Unique Features

		There are a some features of Linux that are especially useful and sometimes unique when compared to other operating systems.

		The /proc file system Linux has a process file system, which serves as an interface to kernel data structures. It presents statistics, status information, and configuration data in a machine independent way accessible as a set of files. The /proc file system doesn't actually exist on your hard drive, but is made to appear that way for ease of use. By doing this, system information and devices can be manipulated by standard tools and remotely accessed through a network file system instead of using special tools specifically defined for that purpose. For example, system memory information can be obtained simply by reading the file /proc/meminfo.

		Loadable kernel modules Linux has always been highly customizable, but in the early years, customizations always required that you recompile the kernel. Though not overly difficult, compiling a kernel can be a tricky business that may present non-programmers a certain amount of difficulty. In addition, kernel compilation can be a lengthy process that is undesirable when all you want to do is add support for a sound card. These inconveniences gave way to the idea of loadable kernel modules, which are dynamically loaded extensions to a monolithic kernel. This approach yields many of the advantages of a microkernel without the performance impact. In a Beowulf system, loadable modules make system management a much easier task. It avoids the need to recompile a kernel, install it on every node of the system, and reboot every node. Instead, only the particular feature being added needs to be compiled as a module, and then installed on every node without rebooting a single machine.

		Virtual consoles A problem endemic to many operating systems is that they have only one user console. If the window system freezes, or some other error occurs, there is no way to recover without rebooting the machine. In addition, it is not possible to use the system effectively in text-only mode, if such a mode is even possible. Linux originally ran on PCs that sometimes had insufficient memory to run an X server. Also, many users simply had no need for a window system, and could work effectively from a text console. Therefore a virtual console system was added to Linux from the very early stages. The virtual console system allows you to simultaneously maintain separate login sessions. You can run an X server in one console, hit a function key combination and be presented with a text-only