Reddit reviews Building Embedded Linux Systems: Concepts, Techniques, Tricks, and Traps

Oh hell no. I have much less time to play and tinker than I did in my 20s/college years. All/most of the current and new understanding does come from my background but mostly my jobs.

I started as a system admin, loved Linux so much I focused on that, got a job as a mid, then a job as a senior Linux SA. My senior SA job was for a small electronic research lab and I once I had their environment solid and automated I had more free time for other work so I took on more typical System Engineer duties and worked on their software build environments. Git/Jenkins/Compilers (GCC, Intel CC, and Intel Fortran) as well as migrating their build code from M4/autotools to CMAKE and Python. Anyways, they also had side projects for porting their code-base to new mobile devices so I learned a lot from that. Simple programs are really as easy as having your toolchain in place and build...but the easiest would be just get say a Raspberry Pi and natively compile.

I might recommend a good book co-authored from Jon Masters, the Chief ARM Architect at Red Hat (great guy IRL BTW, had a few pints few years back at a conference. We both used to be quite fat/obese so we hit it off about that and Linux/ARM)

https://www.amazon.com/Building-Embedded-Linux-Systems-Techniques/dp/0596529686

But back to your original point; I'm in my mid thirties but already see people 10 years younger than me that know the newest tools and shiny new things but I have a more solid understanding of the big picture. My advice is find a niche, focus on it, but also make sure you know/understand everything else. You would be amazed how quickly you can go from not ever touching a new tech or piece of software to a good understanding as long as you have that core fundamentals down.

It just takes years of moving around and touching everything you can get your hands on and loving every bit of it. That is key to this field, you have to love it.

Edit:

You really want to learn Linux and compiling then do the Linux From Scratch.

http://www.linuxfromscratch.org

As already mentioned Mastering Embedded Linux Programming is a very good book about the topics you're interested in. Did you also have a look at Building Embedded Linux Systems? There is also Embedded Linux Primer, 2nd Edition, by Chris Hallinan, or Linux for Embedded and Real-Time Applications, 3rd Edition, by Doug Abbott, which are very good. Each covers the topics you're interested in; by the end of the day it's quite subjective which writing style you prefer.