The first ever zine I wrote, in 2015, was about strace, a tool for tracing system calls. I wrote it all with a sharpie, painstakingly photocopied it at a Staples, and printed 200 copies to give out at a talk called A swiss army knife of debugging tools. (you can see the scanned Sharpie zine in all its original glory here).
The reason I bothered to do all this was that strace is an AMAZING TOOL that lets you see what ANY LINUX PROGRAM IS DOING. Any program! You don't need to have the source code! It's one of my go-to tools for figuring out why an unfamiliar program is doing something weird, and I like it so much that I wrote 9 blog posts about strace in 2014-2015. If you want to know more, you should read the zine! (Spying on your programs with strace)
These 2 pages from that zine explain my favourite 6 strace command line flags.
The full zine is called Spying on your programs with strace, and you can read it for free! I redid it on an iPad (which is what I use now to draw) from the original scanned Sharpie version to make it a little easier to read.
The zine: Spying on your programs with strace