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First time making a mc server on a vps, ive made them in the past on serverhosts and local. This is my error log, what is going on?? https://pastebin.com/AuE5FyR9

I looked up on how to do this and it says to use cron, I've never used cron, so how would I go about doing this?

- I need them to delete every time it exceeds a certain folder size
- I need only .jpg files to be deleted