To find all folders and it's disk usage sorted by size, you can use the following cmd

du -ck | sort -n

To find all files in a folder and it's size,

ls -l --block-size=MB

or

ls -lh

you can execute the following cmd to find the process which occupies a specific port in linux.

sudo lsof -i :<port_number> -t | xargs ps -o pid,user,cmd -p

"Must have or we look stupid" is applicable all the tasks that you do, all the questions that you ask to everyone. Say you're developing a login / signup page. at base minimum it should handle positive login and negative login cases. extensive validations, unique username check comes after those first two cases. Say all the testing is completed and we launched it to production. As a first step QA engineer will do a sanity of those bare minimum cases. if those didn't work, ultimately we will be stupid in-front of your customers right?. but have we thought about this while we ask questions to others. before asking questions to our seniors or fellow developers, we should have explored / tried very obvious solutions first ourselves. most of your team mates will be helpful even if you ask stupid questions. but doing basic exploration is the justice we can do those helpful people. and also yaa, we don't need to look stupid after asking a silly question. be a QA engineer for your own questions.