How to add SILGYDIR to sudoers

This is required only if you want to listen to the port below 1024, i.e. standard HTTP port 80, or HTTPS 443.

Without it sudo won't see your environment variable.

sudo visudo

then find the block starting with Defaults env_reset and add the new line like this:

Defaults    env_keep += "SILGYDIR"

(If you don't know vi editor yet, here is a cheat sheet.)