I've been considering moving an app off of Heroku and to Digital Ocean so I could learn the ropes of administrating a Linux server but I feel there's so much I

I've been considering moving an app off of Heroku and to Digital Ocean so I could learn the ropes of administrating a Linux server but I feel there's so much I don't know that I should know if I wanted to effectively manage my own server. If I got hacked with m64.pl, I'd get as far as running top and killing the process. His immediate assumption was that someone got a file that file on to his server and so he went on to check the logs and found all the failed login attempts. I would have wondered what the file was, googled around and sat around confused. Luckily deploying a new instance on Digital Ocean sounds simple enough so I would probably just do that but that approach would leave me with a sense that I don't know what I'm doing at all. There was a time when my solutions to problems on Windows machines was to restart and/or format but I don't do that anymore but still meet people who do. I'd rather not start from square 1 when I make the leap to Linux. What are the things one should know to legitimately say they can manage their own Linux server? I could try to just wing it and solve every problem as I encounter them but for right now I'd just like to identify the gaps in my knowledge.