The proc pseudo file-system

The /proc directory on GNU/Linux systems provides a file-system like interface to the kernel. This allows applications and users to fetch information from and set values in the kernel using normal file-system I/O operation.

The proc file system is sometimes referred to as a process information pseudo-file system. It does not contain ``real'' files but rather runtime system information (e.g. system memory, devices mounted, hardware configuration, etc). For this reason it can be regarded as a control and information center for the kernel. In fact, quite a lot of system utilities are simply calls to files in this directory. For example, the command lsmod, which lists the modules loaded by the kernel, is basically the same as 'cat /proc/modules' while lspci, which lists devices connected to the PCI bus of the system, is the same as 'cat /proc/pci'. By altering files located in this directory you can change kernel parameters while the system is running.

The proc(5) manual page describes most entries in detail.