How to keep two folders automatically synchronized?

Question

I would like to have a synchronized copy of one folder with all its subtree.

It should work automatically in this way: whenever I create, modify, or delete stuff from th

Answer 1

Just simple modification of @silgon answer:

while true; do 
  inotifywait -r -e modify,create,delete /directory
  rsync -avz /directory /target
done

(@silgon version sometimes crashes on Ubuntu 16 if you run it in cron)