I solved the problem, and once I found the right plugin it was pretty easy! The docker image I am working with is Technitium DNS
I set the docker container network to "host"
I installed CA User Scripts and created a new user script called enable-nginx-extensions with the following:
#!/bin/bash
# remove the config file if it already exists
rm /etc/nginx/conf.d/nginx_extend.conf
# symlink to the config file stored on the boot volume with the user script
ln -s /boot/config/plugins/user.scripts/scripts/enable-nginx-extensions/nginx_extend.conf /etc/nginx/conf.d/
# restart nginx so that the new configuration file is picked up
/etc/rc.d/rc.nginx restart
I created a configuration file and stored it at /boot/config/plugins/user.scripts/scripts/enable-nginx-extensions/nginx_extend.conf
server {
listen 80;
server_name new_server_name.local;
location / {
proxy_pass http://localhost:5380/;
allow all;
}
}
A couple of things to take note of:
You must specify a server name - unraid is the default server and you can't change that. it has to be that way. Don't fight it
Set the proxy_pass line to the ip/port where the upstream server is serving your application
The allow all line is very important - without it, the application will try to authenticate the user against the unraid auth. This is almost certainly not what you want.
I set the script to run at array start.
I verified that my new site was available and restarted things a couple of times to make sure it persisted.
I hope these steps help someone else out in the future!