About

The compose file references the image docker.internal:5000/caddy:latest that does not exist publicly because the image was built using the provided caddy Dockerfile that compiles additional modules for caddy.

The configuration:

    cap_add:
      - NET_ADMIN

specifies that caddy is able to run on privileged ports (required due to caddy being configured to be a front-facing reverse-proxy).

Source

version: '3.7'

services:
  caddy:
    image: docker.internal:5000/caddy:latest
    cap_add:
      - NET_ADMIN
    ports:
      - "80:80"
      - "443:443"
      - "443:443/udp"
    volumes:
      - /mnt/docker/data/caddy/etc/Caddyfile:/etc/caddy/Caddyfile
      - /mnt/docker/data/caddy/etc/auth:/etc/caddy/auth
      - /mnt/docker/data/caddy/site:/srv
      - /mnt/docker/data/caddy/data:/data
      - /mnt/docker/data/caddy/config:/config