I see. Thanks for explaining that.

The problem with this is that, according to man bash, type -p only...

In other words, it just checks if $program is in your $PATH, not if it is executable.

So, the right way to perform that check would be to use text -x, but with proper quoting:

if [ -x "$(type -p "$program")" ]
then
  [commands]
else
  [commands]
fi

Instead of merely insulting FreeBSD/TrueOS, could you (in a new thread) provide reasons for why you think using these systems is "like taking a leap to 2 decades back" and a waste of time? I would be very much interested, since I've recently tried FreeBSD (but not TrueOS) and taken some notes about my experience.

As far as I can see, all window managers are "dbus-free". dbus is, for example, required by file managers for mounting external devices. See: https://dev1galaxy.org/viewtopic.php?pid=1028

That's why you would probably want to have

exec dbus-launch --exit-with-session openbox-session

instead of just

exec openbox-session

inside your ~/.xinitrc file. At least when using Thunar or PCManFM.

If that is an official Devuan installation image, then why isn't it to be found in the Devuan release archive?

I actually didn't want to go into this (for perceived lack of sufficient qualification), but as it has been bugging me all day, let me say a few words about why I expressed the assumption that reading the manual may not be the best way of "getting under the hood".

Simply put, my experience with learning parts of how GNU/Linux or a specific distribution work and how to do things on these systems sort of contradicts the idea of sitting down, reading the book, going through some practical examples and then being a more competent user. That rather reminds me of dull introductory courses at university where I've never really learned anything. I'm really far from being a GNU/Linux expert, but the knowledge I've acquired so far mainly came from trying to solve actual problems I encountered. These included tweaking my desktop environment, wanting to find a better backup solution, trying to get hardware to work that wouldn't out of the box, finding ways of stripping down the system so it would be easy on resources, wanting to auto-generate a bunch of HTML pages, wanting to share files locally and over the network etc.

So, in reference to the Debian Administrator's Handbook, I'd say you best be your own case study. You could just start by asking yourself: Where are the rough edges of my setup? Which problems do I regularly run into using this system? Is there anything that I find kind of hard to do that may be done in a better way?

This apporach really has its advantages: Your "getting under the hood" will start from your personal perspective and use case. This not only avoids the delicate question „Why am I reading this?“, it also helps you limit your endeavors, letting your knowledge and skills evolve gradually instead of going full in, getting unnecessarily confused, not really knowing what to do with all the information later on and surely forgetting most of it in no time.

However, this doesn't mean you shouldn't be dealing with the concepts and inner workings of GNU/Linux or Devuan or computers and software in general. If you really try to solve a problem and understand the what and why of it's solution, you may actually have to read a lot of background documentation (like, e. g., parts of the Wheezy book), but it will still relate to what you want to achieve.

Also, when I read documentation in order to solve a problem and finally find a proper way to do it, I'll write it up and add it to my personal collection of documents on how to do this and that on GNU/Linux. This really helps a lot.

Unfortunately, the "browse online" link in that article points to the book for Debian Jessie. The Wheezy version can be found at https://debian-handbook.info/browse/wheezy/.

Btw, I'm not quite sure if reading these books is the best way to learn your way around Devuan and GNU/Linux in general. But it won't do any harm either, I guess.

If this is really just about finding a lightweight and stable window manager to use, I suggest that you take a good look at Openbox (or Fluxbox) before investing time in fixing bugs in a piece of software that apparently hasn't really been maintained for over a decade. Openbox etc. also are surely used much more widely than Blackbox these days, which means that they get a lot more testing and feedback.

If you should find Openbox useful, there's also some packaging work for Devuan to be done: Back in Debian Wheezy there used to be a package openbox-themes in the repositories which was later dropped. I've recently installed that package on Devuan Jessie and it worked just fine. So, I think it should be easy to re-package that for Devuan, including some additional themes.

If you're still interested in hacking Blackbox, you might want to have a look at https://github.com/bbidulock/blackboxwm.

I generally see your point. However, we decided not to include that info because if there is one piece of information on Devuan that you really don't have to hunt for, it is Devuan being a fork of Debian. It's right there on the front page at devuan.org: "Devuan GNU+Linux is a fork of Debian without systemd."