Marcus Ahlberg's questions

I'm trying to host the Unifi Controller in a docker container but I can't adopt a new device (access point) unless I set networking mode to "host". I have followed several guides and opened all ports listed here. It's possible to manage already connected devices and to find new devices but adopting them results in a never ending "adopting" status.

The first configuration is based on jacobalberty/unifi:

version: "3.7"

services:
  controller:
    image: jacobalberty/unifi:arm32v7
    restart: unless-stopped
    init: true
    volumes:
      - ./data:/unifi
    environment:
      TZ: "Europe/Stockholm"
    ports:
      - "3478:3478/udp"
      - "5514:5514/udp"
      - "8080:8080"
      - "8443:8443"
      - "8843:8843"
      - "8880:8880"
      - "6789:6789"
      - "27117:27117"
      - "5656-5699:5656-5699/udp"
      - "1900:1900"
      - "10001:10001/udp"
#    network_mode: "host"

The other is a direct copy of linuxserver.io example:

version: "2.1"
services:
  unifi-controller:
    image: linuxserver/unifi-controller
    container_name: unifi-controller
    environment:
      - PUID=1000
      - PGID=1000
      - MEM_LIMIT=1024M #optional
    volumes:
      - ./data:/config
    ports:
      - 3478:3478/udp
      - 10001:10001/udp
      - 8080:8080
      - 8443:8443
      - 1900:1900/udp #optional
      - 8843:8843 #optional
      - 8880:8880 #optional
      - 6789:6789 #optional
      - 5514:5514 #optional
    restart: unless-stopped

The docker container is running on a Raspberry Pi connected to wired network. The host is running other containers but there are no conflicting ports. If there were port conflicts it shouldn't be possible to start the container anyway.

I've created a docker container that runs postfix in the foreground using postfix start-fg. It starts fine but is having trouble resolving hostnames, which I think is due to that /var/spool/postfix/etc is missing. This is mentioned in a comment here but without any explanation or reference.

There is a workaround described here, with a vague explanation and no sources.

Is this described in the official documentation or is it just something that people discover after hours of debugging?