Mastering Embedded Linux Programming - Second Edition

The proc and sysfs filesystems

proc and sysfs are two pseudo filesystems that give a window onto the inner workings of the kernel. They both represent kernel data as files in a hierarchy of directories: when you read one of the files, the contents you see do not come from disk storage; it has been formatted on-the-fly by a function in the kernel. Some files are also writable, meaning that a kernel function is called with the new data you have written and, if it is of the correct format and you have sufficient permissions, it will modify the value stored in the kernel's memory. In other words, proc and sysfs provide another way to interact with device drivers and other kernel code. The proc and sysfs filesystems should be mounted on the directories ...