Chapter 16. File System Hierarchy

An LSB conforming implementation shall provide the mandatory portions of the file system hierarchy specified in the Filesystem Hierarchy Standard (FHS), together with any additional requirements made in this specification.

An LSB conforming application shall conform to the Filesystem Hierarchy Standard.

The FHS allows many components or subsystems to be optional. An application shall check for the existence of an optional component before using it, and should behave in a reasonable manner if the optional component is not present.

The FHS requirement to locate the operating system kernel in either / or /boot does not apply if the operating system kernel does not exist as a file in the file system.

The FHS specifies certain behaviors for a variety of commands if they are present (for example, ping or python). However, LSB conforming applications shall not rely on any commands beyond those specified by the LSB. The mere existence of a command may not be used as an indication that the command behaves in any particular way.

The following directories or links need not be present: /etc/X11 /usr/bin/X11 /usr/lib/X11 /proc

16.1. /dev: Device Files

The following shall exist under /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.


An infinite data source and data sink. Data written to this device shall be discarded. Reads from this device shall always return end-of-file (EOF).


This device is a source of zeroed out data. All data written to this device shall be discarded. A read from this device shall always return the requested number of bytes, each initialized to the value '\0'.


In each process, a synonym for the controlling terminal associated with the process group of that process, if any. All reads and writes to this device shall behave as if the actual controlling terminal device had been opened.