I find it useful to write down commands or series of commands in a simple notebook to refer to when needed for specific tasks. That is especially helpful for occasional housekeeping tasks and running CLI utilities e.g. Rkhunter etc. Maybe this thread can also become a "notebook" of useful commands.
The CLI is powerful, but should not be frightning to the user. I would reitterate what others have mentioned on the forum elsewhere. Read the screen output carefully before clicking "Y".
It is like reading the small print of T&C's. Just take time to make sure you understand what you are committing to doing and you will be alright.
As I have limited disk space. In addition to cleaning apt, I use the following commands (from my notebook) to
recover space taken by journal files:
check disk usage:
journalctl --disk -usage
review:
journalctl -r
start new, archive old:
sudo journalctl --rotate
limit size to 100M and clean:
sudo journalctl --vacuum-size=100M
I hope I have written that correctly, or @Aravisian will correct me.