@julian Honestly, I wouldn't
chmod, just delete and reinstall (or move) in a more appropriate location, and then adjust permissions (if still necessary).
@Wojciech-Lisik You shouldn't install programs in
/usr/, but rather something more like
/usr/local/opt/ or, ideally, some subdirectory under your user's home directory (for development). If you're setting up a production server, you'd want to create some directory structure under
/etc/ owned by a special, non-root user with the least privilege possible. Most of my setups follow the paradigm of storing server files hosted by NGINX under
/usr/share/nginx/ and setting rwx privileges to the special user I set up only in that folder.
You should never have to use
sudo or the root login to install nodebb (or any other web software, for that matter), and doing so can be a huge security risk.
Here's a neat Superuser answer that outlines what the intended usage of each folder in a *nix machine is for.