NGINX Proxy Manager cannot resolve hostnames from docker
reddit / selfhosted

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CtKairos · 2023-12-13 20:31

Hello! I've been banging my head on this for quite a while: I've got
NGINX Proxy Manager set up with Pihole to make it easier to access my
internal services (nothing is exposed to the public for now). Every
docker container I have is on the same server.  I've managed to get it
all working, except for in the proxy hosts of NPM I for some reason
can't use hostnames from docker containers in the IP Address., even
though they are on the same docker network. I've tried both ways for
the docker network, all services added to the NPM network or NPM added
to individual networks, but both have issues with resolving the
hostnames. I've checked the hostnames with `docker exec -it  hostname`
and checked the docker network with `docker network inspect ` and I've
also tried inside of nginx container to curl the hostname like this
`docker exec -it nginx curl http://service_name` and ping it and both
seem to be working fine. The weirdest part is some of the hostnames do
resolve and npm successfully proxies to the correct address, but not
all. For example, here is my docker compose for my two radarr
instances:

```
version: "3.8"
services:
  radarr:
    image: lscr.io/linuxserver/radarr
    hostname: radarr
    container_name: radarr
    environment:
      - PUID=${PUID}
      - PGID=${PGID}
      - TZ=${TZ}
      - UMASK=002
    volumes:
      - ${BASE_DOCKER_DATA}/radarr/hd:/config
      - /mnt/shared/data:/data
    restart: unless-stopped
    ports:
      - 7878:7878
    networks:
      - media-network
  radarr4k:
    image: lscr.io/linuxserver/radarr
    hostname: radarr4k
    container_name: radarr4k
    environment:
      - PUID=${PUID}
      - PGID=${PGID}
      - TZ=${TZ}
      - UMASK=002
    volumes:
      - ${BASE_DOCKER_DATA}/radarr/uhd:/config
      - /mnt/shared/data:/data
    restart: unless-stopped
    ports:
      - 7879:7878
    networks:
      - media-network
networks:
  media-network:
    name: media-network
    external: true
```

both are defined exactly the same, but the non4k one can be accessed
by hostname while the other cannot, which is super strange (media
network is declared elsewhere). Here is my nginx proxy manager compose
if it helps too:

```
version: '3.8'
services:
  nginx:
    container_name: nginx
    hostname: nginx
    image: 'jc21/nginx-proxy-manager:latest'
    restart: unless-stopped
    ports:
      # These ports are in format :
      - '80:80' # Public HTTP Port
      - '443:443' # Public HTTPS Port
      - '81:81' # Admin Web Port

    volumes:
      - ${BASE_DOCKER_DATA}/nginx/data:/data
      - ${BASE_DOCKER_DATA}/nginx/letsencrypt:/etc/letsencrypt
    environment:
      - PUID=${PUID}
      - PGID=${PGID}
    networks:
      - proxy_net
      - media-network
networks:
  proxy_net:
    driver: bridge
    name: proxy_net
  media-network:
    name: media-network
    external: true
```

please let me know if I am doing something stupid here or I am missing
something, this is all super new to me and I am sure I missing
something in here! :)