By using an adblocker, it is possible to hide a large part of the advertisements displayed on the Internet. If you are looking for a central adblocker for your home network, you should take a look at the adblocker Pi-hole. Pi-hole is an open source DNS server with integrated tracking and ad blocker. Pi-hole runs on popular Linux systems and can thus be run on a Raspberry Pi or in a Docker container, among other things.

To ensure that the DNS queries of all devices in the network are answered by Pi-hole, the IP address of Pi-hole can be stored centrally on the router as a DNS server. Devices with automatic address assignment: DHCP, thereby use Pi-hole as DNS and thus its advertising filter. As an example, in the free router firmware OpenWRT, the DNS can be adjusted as follows: OpenWRT - my setup. I use Pi-hole as Docker container on my NAS, see also: Build NAS yourself: flexible, power saving and cheap [HowTo].

docker-compose.yml

Since port 80 on my NAS is already occupied elsewhere, I use a slightly customized version of the manufacturer's docker-compose.yml:

version: "3"

# More info at https://github.com/pi-hole/docker-pi-hole/ and https://docs.pi-hole.net/
services:
  pihole:
    container_name: pihole
    image: pihole/pihole:latest
    ports:
      - "53:53/tcp"
      - "53:53/udp"
      - "67:67/udp"
      - "84:80/tcp"
    environment:
      TZ: 'Europe/Amsterdam'
      WEBPASSWORD: 'password'
    # Volumes store your data between container upgrades
    volumes:
      - './etc-pihole/:/etc/pihole/'
      - './etc-dnsmasq.d/:/etc/dnsmasq.d/'
    # Recommended but not required (DHCP needs NET_ADMIN)
    #   https://github.com/pi-hole/docker-pi-hole#note-on-capabilities
    cap_add:
      - NET_ADMIN
    restart: always

In the file, port 84 is mapped to 80. Accordingly, the admin interface is later accessible under the IP address of the NAS with port 84. In addition, I have filled the variable "WEBPASSWORD" with a secure password. The example uses bind mounts and not docker volumes to permanently store data. See: Docker data storage: Docker Volumes vs. Host Folders

The container is started in the terminal with the following command: 

docker-compose up

At the first start I had a problem with port 53, it was already occupied on my NAS:

Ubuntu/Debian port 53 occupied.

Since my NAS uses Debian, the systemd-resolv service blocks DNS port 53. So that port 53 can be used for the Pi-hole Docker container, I disabled the systemd-resolv service.

user@rechner:/docker/pi-hole$ sudo netstat -tulpn | grep LISTEN
...
tcp        0      0 127.0.0.53:53           0.0.0.0:*               LISTEN      1279/systemd-resolv
...

user@rechner:/docker/pi-hole$ sudo systemctl disable systemd-resolved.service
Removed /etc/systemd/system/dbus-org.freedesktop.resolve1.service.
Removed /etc/systemd/system/multi-user.target.wants/systemd-resolved.service.
user@rechner:/docker/pi-hole$  sudo systemctl stop systemd-resolved

Admin interface

The admin interface is called in the browser with the IP address of the NAS and the previously used port 84:

http://x.x.x.x:84/admin

Pi-hole uses a predefined blacklist and shows statistics about the clients and the allowed, as well as blocked domains already on the start page:

In addition to Pi-hole, I currently use the DNS servers of OpenDNS as upstream DNS servers to banish adult content from the home network as far as possible. See: child-safe Internet via the home network - DNS on the router

In Pi-hole, the setting for the upstream DNS server is located under Settings/DNS: