Excellent open source
Open Source Ecology - World of collaborative design – for a transparent and inclusive economy of abundance
Linux kernel - Linux is a clone of the operating system Unix, written from scratch by Linus Torvalds with assistance from a loosely-knit team of hackers across the Net. It aims towards POSIX and Single UNIX Specification compliance.
Void Linux - Void is a general purpose operating system, based on the monolithic Linux kernel. Its package system allows you to quickly install, update and remove software; software is provided in binary packages or can be built directly from sources with the help of the XBPS source packages collection.
ysap - Series on bash scripting
The Complete Bash Course - The official YSAP Bash course