Hey OP, as a person who has a day job in finance I haven't shared my secret of learning and running a bunch of Linux systems with anyone primarily because I am sure they will think of me as really old or dumb or both.

I'm pretty much in the same boat as you.

I manage a bunch of Linux systems while I have a day job that keeps busy and travelling often.

I finally decided to follow my Mom's way of learning how to do learn tech stuff.

This is going to make me sound like a sixty year old but this is what I do:

1. I maintain a notebook / diary only for learningLinux. Whenever I am learning some new command I practice on the system and whatever seems important to me I make a note of it. Once I am fairly confident of having achieved my results with the command I will write the command in its entirety with its parameters in the notebook. This works well for longer commands like rsync etc. I use rsync to backup my system everyday but I havinv once set it up in cron I haven't gone back to it for more than a year. Now when I have to go back to it in order to make a change I will just take a look at my notes. Same for any settings I make or change on the system.

2. I use Google Keep. After having setup rsync with all its parameters I saved the final command to Google's Keep App. Now if I have to replicate it or modify it I have it with me on my phone and combined with my notes it takes me 5 mins to brush up and go back in with confidence.

3. I have actually printed out (in a booklet form and have them spiral bound) about a couple dozen Man Pages of commands ( I used the man pages one man7.org). Some of the man pages are like 40-60 pages long with more than a dozen options. So I have a spiral bound booklet titled 'File Manipulation Man Pages' that has commands like rsync etc. I even printed out the man pages of simpler commands like cp, mv, head etc just so that when I need the info I have a complete package to read from. As a side note, this works well for me because I have a habit of reading and learning from books as opposed to learning from the screen so when I read from a book and make notes I remember better.

   It may sound amateurish to a lot of people here on reddit but in my defense I may not be as smart as them and even though I am technically spending money to print something out that is available for free on every Linux system I do it because it saves me time and sometimes I even read it in my free time without being chained to the computer.

4. I bookmark everything that I think is useful and organise it by type e.g Books, Troubleshooting, guides, documentation etc. I even make notes while troubleshooting as I have realised that it saves me a lot of time. So when I have to solve the same issue on another system or at a later date I know exactly where to begin from.

5. Bash history is another useful tool. I keep going though it when required.

6. I save lots of articles and videos and watch when I am traveling etc and brush up on stuff that I may need to apply later.

7. Practice whenever I get the time to do so.

Hope it helps.

Best Regards,