I’ve always wanted to learn the specifics of how Linux works i.e. the kernel and internals. While learning higher level tools is all fine and will help you to do your 90% of your job, to become a better engineer you’ll have to learn the lower level interfaces of the systems you work with.

I’ll be starting with the book The Linux Programming Interface. Chapter 1 of tlpi covers the history of Unix, the C programming language, GNU project and the Linux kernel along with a bunch of stuff about POSIX standards and the Single Unix Specification. I’m sure I’ll not retain all the details, specifications and the years in which these were released, but the info in this chapter is common knowledge to anyone who has taken even a rudimentary interest in the history of operating systems.

POSIX(portable operating system interface) - which specifies the standards that an OS must adhere to in order to be POSIX compliant, which Linux mostly does

There is also the distinction between kernel and what passes as the operating system as whole in common parlance(kernel + other tools like shells, GUI, editors, compilers etc)

Basically this chapter is a good summary of the complicated history of Unix, C, Linux and the jumble of standards from which POSIX has emerged.