os: expand on linux overview

Author: practicalli-johnny

docs/os/linux/index.md

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+# Linux  Operating System
+
+Linux is an open source kernel with a very large collection of software tools.
+
+Linux is typically installed via a distribution, a community or commercial effort to package that large collection of software so that it is easy to install and maintain.
+
+Most commonly used Linux operating system
+
+- Debian Linux & Ubuntu
+- Red Hat & CentOS
+- Arch Linux
+- OpenSUSE
+- Slackware Linux
+
+There are 100s of Linux distribution, typically based on one of the above.
+
+
+## Packaging Standards
+
+Deb package is a well defined standard that helps avoid conflicts between software and its package dependencies.  The standard ensures consistency across all packages.
+
+RPM is a simpler package design and has less strictness for managing dependencies.
+
+Arch is described as a rolling release, although occasionally the install ISO is updated.  Packages are continually updated in the Arch repository.  Arch User Repository contains community managed packages, each package is built from Git repositories.