= Device node
A \b[device node] is a special <file system> object through which a program accesses a device interface. In the Linux model, its <inode> records a device-special file type and a <device number>; the path supplies a name in the <file-system namespace>. Opening it supplies a <file descriptor> through which the applicable <device driver> handles operations. Device-special objects differ from ordinary files containing a stored byte sequence.<Device file metadata in the Linux man-pages project>[inode(7), device ID and file types; mknod(2), DESCRIPTION]{ref}
Two device identifiers must be distinguished. The metadata field `st_dev` identifies the device containing the <file system> that holds the inode. For a <character device> or <block device>, `st_rdev` instead identifies the represented device. Its major and minor numbers belong to that represented-device identification. The inode's own number is a third identifier.<Device file metadata in the Linux man-pages project>[inode(7), Device where inode resides and Device ID; mknod(2), dev argument]{ref}
For an original metadata example, stipulate that names `/dev/example-a` and `/dev/example-b` reach different inodes numbered 42 and 43 in one file system. Both inodes have character-device type and represented-device numbers `(240,7)`. They name the same device interface in this example despite being different named file-system objects. Different permissions on the nodes can still affect access. Their inode numbers alone do not identify two physical devices.
A <character device> presents a driver-defined stream or control interface; it need not contain human-readable characters. A <block device> presents block-oriented storage access. The special-file type is part of the identification, so equal numerical major/minor pairs do not alone equate character and block interfaces. A <video device node> is a concrete <Video4Linux> example, whose supported functions must still be queried.
Creating a device-special file supplies a namespace entry and device identification; it does not manufacture hardware, load a guaranteed working driver or establish a supported data format. Conversely, a <symbolic link> pointing to a device node is an ordinary naming indirection: its target's special-file metadata determines the accessed interface.
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