/dev : Devices and special files

The following devices must exist under /dev.

/dev/null: All data written to this device is discarded. A read from this device will return an EOF condition.
/dev/zero: This device is a source of zeroed out data. All data written to this device is discarded. A read from this device will return as many bytes containing the value zero as was requested.
/dev/tty: This device is a synonym for the controlling terminal of a process. Once this device is opened, all reads and writes will behave as if the actual controlling terminal device had been opened.

Previous versions of the FHS had stricter requirements for /dev. Other devices may also exist in /dev. Device names may exist as symbolic links to other device nodes located in /dev or subdirectories of /dev. There is no requirement concerning major/minor number values.