Customize docker bridge subnet

custom_docker_bridge_subnet.md

Change the Docker Daemon's Startup Options (systemd)

1. Stop docker daemon: sudo systemctl stop docker

2. Override the docker daemon startup options via systemd by adding a conf file

    sudo mkdir -p /etc/systemd/system/docker.service.d
    sudo vim /etc/systemd/system/docker.service.d/docker.conf
   

3. Override the ExecStart command and add the --bip option

    [Service]
    ExecStart=
    ExecStart=/usr/bin/dockerd -H fd:// --bip=198.18.0.1/24
   

4. Install bridge-utils: sudo apt-get install -y bridge-utils

5. Bring down and delete the docker0 bridge.

    sudo ip link set down docker0
    sudo brctl delbr docker0
   

6. Reload systemd daemon: sudo systemctl daemon-reload

7. Start docker: sudo systemctl start docker

Note:

If you created bridged other than docker0 you need to use docker command, docker network rm ... to remove them (i.e. the brctl delbr ... command is not enough because the docker daemon will recreate them).

example_docker_compose.yml

# Control the bridge subnets created by docker-compose

version: '2'

services:
  web:
    image: ubuntu
    tty: true
    networks:
      mynet:
        ipv4_address: 198.18.1.2

networks:
  mynet:
    driver: bridge
    ipam:
      driver: default
      config:
        - subnet: 198.18.1.0/24
          gateway: 198.18.1.1