Hello there! Here’s the thing: I got some old HDD for my Debian home server, and now that I have plenty of disk space I want to keep a backup of the OS, so that if something accidentally breaks (either SW or HW) I can quickly fix it.
now the question is: which directory should I include and which should I exclude from the backup? I use docker a lot, is there any docker-specific directory that I should back up?
You need to make your own plan about what’s important to you. Don’t waste time backing up stuff you can quickly download again - like docker images. Just know where the stuff is that you care about (such as any mounted volumes in docker with your own data on) and back that up, and make everything automated. If you do it manually, chances are you’ll gradually stop doing them.
I wrote some things about properly backing up data that may be of use.
Maybe try setting up a local Gitea instance with a Docker registry.