This will allow you to access an Octoprint instance (or even multiple instances) from a single web server. Most commonly, this is used on a public-facing web server with HTTPS enabled.

Normally, setting this up a reverse proxy is straightforward, but the weird webcam support in Octoprint makes this a little tricky.

First, install nginx per normal, and set up a basic domain config in /etc/nginx/sites-available/<your_domain>. You can enable HTTPS at this time with certbot. That's all out of scope for us.

Next, edit the web server /etc/nginx/sites-available/<your_domain>. This example shows two Octoprint instances (with two location blocks per instance):

    location ~ ^/webcam/(.*) {
        rewrite ^/webcam/(.*) /printrbot/webcam/$1 redirect;
    }

    location /printrbot/ {
        if ($scheme != "https") {
            rewrite ^ https://$host$uri permanent;
        }
        auth_basic           "OctoPrint: PrintrBot";
        auth_basic_user_file /etc/nginx/passwd-3dprinter.conf;
        rewrite ^/printrbot/(.*)$ /$1 break;
        proxy_pass http://192.168.0.42;
        proxy_redirect ~^http://192.168.0.42/(.*)$ $scheme://$host/printrbot/$1;
        proxy_set_header Host $http_host;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Scheme $scheme;
        proxy_set_header X-Script-Name /printrbot;
        proxy_http_version 1.1;
        client_max_body_size 0;

        location /printrbot/webcam/ {
            auth_basic off;
            rewrite ^/printrbot/webcam/(.*)$ /webcam/$1 break;
            proxy_pass http://192.168.0.42;
            proxy_redirect ~^http://192.168.0.42/(.*)$ $scheme://$host/printrbot/$1;
        }
    }

    # requires tweak to octopi config to use alternate absolute webcam url
    location ~ ^/webcam2/(.*) {
        rewrite ^/webcam2/(.*) /prusa/webcam/$1 redirect;
    }

    location /prusa/ {
        if ($scheme != "https") {
            rewrite ^ https://$host$uri permanent;
        }
        auth_basic           "OctoPrint: Prusa";
        auth_basic_user_file /etc/nginx/passwd-3dprinter.conf;
        rewrite ^/prusa/(.*)$ /$1 break;
        proxy_pass http://192.168.0.46;
        proxy_redirect ~^http://192.168.0.46/(.*)$ $scheme://$host/prusa/$1;
        proxy_set_header Host $http_host;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Scheme $scheme;
        proxy_set_header X-Script-Name /prusa;
        proxy_http_version 1.1;
        client_max_body_size 0;

        location /prusa/webcam/ {
            auth_basic off;
            rewrite ^/prusa/webcam/(.*)$ /webcam2/$1 break;
            proxy_pass http://192.168.0.46;
            proxy_redirect ~^http://192.168.0.46/(.*)$ $scheme://$host/prusa/$1;
        }
    }

Things to note:

• Octoprint (as configured in an Octopi install) expects the webcam to be at /webcam – an absolute URL.
• Thus, the first "location ~ ^/webcam/(.*)" to rewrite it under the new URL.
• Because all Octoprint instances expect their webcam to be at /webcam, we need to tweak things a bit.
• The second Octoprint will map /webcam2 instead of just /webcam; we'll change the config on that instance as well to allow this
• (Note: if you have just once octoprint instance, then you can skip the following steps, and you should be done)

We want to tweak each octoprint instances after the first as follows to give it a unique absolute URL to the webcam. This assumes Octoprint is installed as in Octopi.

Edit /etc/haproxy/haproxy.cfg, and add the two noted lines:

frontend public
        use_backend webcam if { path_beg /webcam/ }
        use_backend webcam if { path_beg /webcam2/ } # <<add this line

backend webcam
        http-request replace-path /webcam/(.*) /\1
        http-request replace-path /webcam2/(.*) /\1  # <<add this line