I tried going down your path and blogged only about stuff that's arcane or interesting tech wise, and it did nothing but cause me writer's block and turn me off blogging. Learn to write for yourself first. If you set up Raspian on a Raspberry Pi over the weekend, write about it! If you popped a CentOS install disk and set up a server, write about that. It doesn't matter if there's 10000 blog posts about the same exac…
Very much this. I find how-to guides to be a very good type of topic to blog about: 1) It serves as documentation for yourself to get back to later on (it has come in useful for myself many times to look back at my blog on how I set up something), 2) It serves as a good guide for others and is how you build your audience. Almost any how-to guide out there misses some information. Not everyone ran into the same issues. Your guide will have some info others who have written similar ones have missed. Similarly, you won't be covering some issues that the next person will write about. Someone googling around setting up their raspberry pi or CentOS server about the exact same issue you had, will find your article (and not any other because other guides didn't mention it), and save hours of time because of your guide. (I have comments on my blog telling me this, despite writing about topics that have hundreds of guides out there about)