Have you ever thought of making your own Linux Distribution? Every Linux user in their journey to Linux thought of making their own Linux distribution, at-least once.
The article mentions a book and provides their own partner link. Looks like this is the real link : https://linuxfromscratch.org/lfs/download.html
From Wikipedia, the free encyclopedia
Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).
Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word “Linux” in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.