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7.3. Overview of Device and Module Handling
In Chapter 6, we installed the Udev package when eudev was built. Before we go into the details regarding how this works, a brief history of previous methods of handling devices is in order.
Linux systems in general traditionally used a static device creation method, whereby a great many device nodes were created under /dev (sometimes literally thousands of nodes), regardless of whether the corresponding hardware devices actually existed. This was typically done via a MAKEDEV script, which contains a number of calls to the mknod program with the relevant major and minor device numbers for every possible device that might exist in the world.
Using the Udev method, only those devices which are detected by the kernel get device nodes created for them. Because these device nodes will be created each time the system boots, they will be stored on a devtmpfs file system (a virtual file system that resides entirely in system memory). Device nodes do not require much space, so the memory that is used is negligible.