ipv6 on docker-pihole

setup.sh

# enable ipv6 in dockerd conf:

# cat /etc/docker/daemon.json
{
  "ipv6": true,
  "fixed-cidr-v6": "2003::/64" # your ipv6. not sure if this is even necessary 
}

# reload daemon conf:
sudo systemctl reload docker.service

# check it loaded okay
sudo systemctl status docker.service

# create ipv6 enabled network
docker network create --ipv6 --driver bridge --subnet "fd01::/64" ipv6


# if you have an existing container:

docker network connect ipv6 pihole
docker network disconnect bridge pihole
docker restart pihole

# modify setupvar.conf:
# cat etc-pihole/setupVars.conf | grep IP
DHCP_IPv6=true
IPV4_ADDRESS=192.168.1.2                    # Docker Host IP
IPV6_ADDRESS=fd00::1111:1111:1111:1111      # Docker Host IPv6

# restart pihole dns
docker exec -it pihole /bin/bash -c 'pihole restartdns'

# updated docker run command
# not tested because I used portainer to modify ENV Variables!

docker run -d \
    --name pihole \
    -p 53:53/tcp -p 53:53/udp \
    -p 9000:80 \
    -p 9001:443 \
    -e TZ="Europe/Berlin" \
    -e ServerIPv6="fd00::1111:1111:1111:1111" \
    -e IPv6="true" \
    -v "$(pwd)/etc-pihole/:/etc/pihole/" \
    -v "$(pwd)/etc-dnsmasq.d/:/etc/dnsmasq.d/" \
    --dns=127.0.0.1 --dns=1.1.1.1 \
    --restart=unless-stopped \
    --network=ipv6 \
    pihole/pihole:latest


# To verify:
dig AAAA heise.de -6 @pihole

# from pihole -t in container
13:30:57 dnsmasq[1137]: query[AAAA] pihole from 172.20.0.1
13:30:57 dnsmasq[1137]: /etc/pihole/local.list pihole is fd00::1111:1111:1111:1111
13:30:57 dnsmasq[1137]: query[AAAA] heise.de from 172.20.0.1
13:30:57 dnsmasq[1137]: cached heise.de is 2a02:2e0:3fe:1001:302::

untested-docker-compose.yml

version: "3"

# https://github.com/pi-hole/docker-pi-hole/blob/master/README.md

services:
  pihole:
    container_name: pihole
    image: pihole/pihole:latest
    # For DHCP it is recommended to remove these ports and instead add: network_mode: "host"
    ports:
      - "53:53/tcp"
      - "53:53/udp"
      - "67:67/udp"
      - "80:80/tcp"
      - "443:443/tcp"
    environment:
      TZ: 'America/Chicago'
      # WEBPASSWORD: 'set a secure password here or it will be random'
      IPv6: 'true'
      ServerIPv6: 'fd00::1111:1111:1111:1111' # your dockerhost ipv6
    # Volumes store your data between container upgrades
    volumes:
       - './etc-pihole/:/etc/pihole/'
       - './etc-dnsmasq.d/:/etc/dnsmasq.d/'
    # run `touch ./var-log/pihole.log` first unless you like errors
    # - './var-log/pihole.log:/var/log/pihole.log'
    dns:
      - 127.0.0.1
      - 1.1.1.1
    # Recommended but not required (DHCP needs NET_ADMIN)
    #   https://github.com/pi-hole/docker-pi-hole#note-on-capabilities
    cap_add:
      - NET_ADMIN
    network_mode:
      - ipv6
    restart: unless-stopped
    

this worked for me from here
tried your option but pihole -d does not find ipv6 addresses

version: "3"
services:
  pihole:
    container_name: pihole
    image: pihole/pihole:latest
    network_mode: host
    dns:
      - 127.0.0.1
      - 1.1.1.1
    environment:
      - TZ=${TZ}
      - WEBPASSWORD=${PIHOLE_PASSWORD}
      - ADMIN_EMAIL=${PIHOLE_EMAIL}
      - DNS1=${PIHOLE_FIRST_DNS}
      - DNS2=${PIHOLE_SECOND_DNS}
      - ServerIP=${HOST_IP}
      - ServerIPv6=${HOST_IPV6}
      - TEMPERATUREUNIT="c"
    volumes:
      - './pihole/pihole/:/etc/pihole/'
      - './pihole/dnsmasq/:/etc/dnsmasq.d/'
    restart: unless-stopped

Note that according to the official documentation, ServerIPv6 is deprecated, and FTLCONF_REPLY_ADDR6 is replacing it.