Start your rethinkdb instance with this flag: --bind all (or bind=all in the configuration file for your instance)

Block external access to the web UI with these two commands: sudo iptables -A INPUT -i eth0 -p tcp --dport 8080 -j DROP sudo iptables -I INPUT -i eth0 -s 127.0.0.1 -p tcp --dport 8080 -j ACCEPT

Install nginx: sudo apt-get install nginx

Create a new virtual host (server block): sudo cp /etc/nginx/sites-available/default /etc/nginx/sites-available/rethinkdb_admin

Edit this file: sudo vi /etc/nginx/sites-available/rethinkdb_admin

to say:

server {
  listen 80;
  server_name domain.com;
  
  location /rethinkdb-admin/ {
    auth_basic "Restricted";
    auth_basic_user_file /etc/nginx/.rethinkdb.pass;
    proxy_pass http://127.0.0.1:8080/;
    proxy_redirect off;
    proxy_set_header Authorization "";
  }
}

where domain.com is the host name (or IP address) of the server running the RethinkDB Admin UI.

Create username and password (make sure you have apache2-utils installed sudo apt-get install apache2-utils): cd /etc/nginx/ htpasswd -c .rethinkdb.pass <username> where <username> is the username you want. The command will ask you to enter the password for the username you chose.

start/restart nginx sudo service nginx start or sudo service nginx restart

Verify it works: Navigate to http://domain.com/rethinkdb_admin where domain.com is the host name (or IP address) of the server running the RethinkDB Admin UI.