If you are a Debian user and want to know your system through the command line, you should get this book: Download the book
It’s free to download and covers some topics that should be helpful to Ubuntu users as well.
In case you want to know more about it, here’s the book review:
Thanks I always like to have books like this even if I am not using them as you never know when they might come in handy with information that you can use, even if that is to help others.
i have been dragging my feet about getting back to my debian partition to install wifi drivers. this may be the perfect reason to take a swing. thanks for the share 
In many ways I prefer debian to ubuntu - and kinda prefer it as a server - however - I always run into the issue of f–king WIFI drivers (as @01101111 mentions above) when I’m installing on a laptop… yeah you can work around this (find the right deb file for non-free and put it on yet ANOTHER USB thumb drive [i.e. other than the one you’re installing from!] - or - plug it into ethernet) - but it’s still a PITA - and Ubuntu doesn’t make you do that…
Also - that book when opened as an epub in Cosmic Cuttlefish - looks awful (using Cosmic’s default epub viewer) - I had to install Calibre to view it properly…
I opened it as PDF and downloaded it without problems via Vivaldi on Mint 19.1. I have never used Debian so thought this would be a good introduction to it. So far it is very readable and I am finding it interesting.
So I read a couple of chapters that interested me in this book and all in all it is a very good introduction to Debian. The problem I see for me personally is that most of the information provided is, let’s say, “not up to date”. I’m sure that most of the stuff in there works right now on the newest Debian, but some stuff in the book is not only old but is getting on the edge of being deprecated or at least it is becoming a bad practice to still use this old stuff, nowadays. So the problem with that is, if someone seriously wants to start using Debian very efficiently and well, by putting time and effort into the book, then by the time they master the content and actually could pass a test for this book’s information, the information itself is already so stale, you basically need to update a lot of your information.
Therefore, as mentioned, all in all this book is a good introduction, but this will remain only as a starting point, if you really want to know current Debian.
i almost always have mine plugged in anyways (and did so when installing), but wanted to get the wifi situated just in case for whatever reason that became unavailable. i am happy to say that i was inspired by this post and another to finally get all of that worked out. i feel a bit more comfortable in my debian partition now so that is a good thing 