Map of Penguin Land

2026-04-30, Thu

Tools and libraries in GNU/Linux system have different origins and people behind them. And itt would be nice to have a clear picture to clarify who defines what, and what is implemented & maintained by whom.

1. The Standards

1.1. Unix standards

Unix standards like POSIX¹, XSI and SUS have relations listed below:

Standard	Managed By	Purpose	Comment
POSIX	IEEE/ISO	Portability across Unix-like OS	Baseline and mandatory core
XSI	The Open Group	Defines traditional Unix behavior	Optional fo POSIX, mandatory for UNIX branding
SUS	The Open Group	Branding of UNIX trademark	Incorporates both POSX + XSI, i.e. the Superset

1.2. Linux standards

Other standards relevant to Linux are listed below:

The Linux Standard Base (LSB)²: specifications are built upon POSIX and add Linux-specific requirements. However, not all distros (including major ones) follow thes specs in recent years.
Filesystem Hierarchy Standard (FHS)³: defines where files and directorys should be located. Most distros follow this closely.
C Standard (ISO C)⁴: Linux's standard C library (usually glibc) follows ISO C standards
Networking Standards from RFC⁵: Linux impoements standard networking protocols defined by RFCs from IETF.

Aside from these standards, Linux Kernel docs⁶ also provides latest API update.

2. The Implementations

Take a closer look at AUTHOR section man pages and we have:

GNU⁷: what's defined in POSIX, et al., e.g. core utils and glibc
Linux: whta's beyond POSIX et al., e.g. util-linux⁸

Other than these two, we also have tools from distro vendors like ReadHat, Debian, or GUI application suite from project like Gnome and KDE, as well as independent projects like FFmpeg, OBS Studio, Blender, etc. They are not related to the UNIX standards, so not listed here.