Ordering page for the Open Group's Single Unix Specification.

Help site and portal documenting all major Unix distributions.

The original Unix users manual.

Source material from Bell Labs.

Brief Unix tutorial, online man pages and reference materials for the Unix operating system and common Unix utilities.

Description of how the filesystem works internally.

Unix tutorials, exercises and resources. Features on-line tests and training materials.

A simple daemon that monitors and limits usage of ttys. It is implemented in Python. A simple config file can specify monthly, daily, session, and idle limits based on tty, user, group, and ttys in use.

Basic as well as more obscure commands for Unix/Linux operating systems.