dnsmasqPXE

use - docker-compose

configure

The simplest configuration is below. This will set up dnsmasq on localhost, and point all localhost DNS queries to itself with 1.1.1.1 and 8.8.8.8 as the DNS servers.

docker-compose.yml

version: "3"
services:
  dns:
    image: trailmix/dnsmasqPXE
    restart: always
    ports:
      - "53:53/udp"
    cap_add:
      - NET_ADMIN

The expansive way to configure is below, this will configure the guest IP address, DNS servers, and interface.
It will also set up reverse lookup and provide DNS on port 8600 for consul. It will set up the guest as a DHCP server with some static address assignments to 4 hosts. It will provide PXE over this DHCP server as well. It will also start a tFTP server with the root of /srv/tftp on the guest.

You will need to provide and configure a DHCP server template, and a tFTP server template as exampled below.

docker-compose.yml

version: "3"
services:
  dns:
    image: trilom/dnsmasqPXE
    restart: always
    volumes:
      - ./config:/etc/dnsmasq.d
      - ./templates:/tmp/templates
      - ./tftp:/srv/tftp
      - ./config.yml:/tmp/config.yml
    environment:
      HOST_IP: "10.0.15.100"
      DNS1: "1.1.1.1"
      DNS2: "8.8.8.8"
      INTERFACE: eth0
      REV_CIDR: "10.0.0.0/8"
      DHCP: "true"
      TFTP: "true"
    ports:
      - "1000:53/udp"
    cap_add:
      - NET_ADMIN

config.yml

tftp:
  range:
    - 10.0.15.20
    - 10.0.15.200
  host: 10.0.15.10
  domain: 7ds.xyz
  root: /srv/tftp
dhcp:
  - name: mgmt
    reverse: 10.0.0.0/8
    range:
      - 10.0.15.20
      - 10.0.15.200
    router: 10.0.15.1
    hosts:
      - name: greed
        address: 10.0.15.10
        mac: ab:cd:ef:12:34:56
      - name: wrath
        address: 10.0.15.11
        mac: ab:cd:ef:12:34:55
      - name: pride
        address: 10.0.15.12
        mac: ab:cd:ef:12:34:54
      - name: lust
        address: 10.0.15.13
        mac: ab:cd:ef:12:34:56

templates/10-consul.conf

expand-hosts
rev-server=REV_CIDR,HOST_IP#8600
server=/consul/HOST_IP#8600

templates/60-tftp.conf

interface=INTERFACE
domain=DOMAIN
dhcp-range=RANGE_LOW,RANGE_HIGH,255.255.255.0,1h
dhcp-boot=pxelinux.0,pxeserver,TFTP_HOST
pxe-service=x86PC, "Install Linux", pxelinux
enable-tftp
tftp-root=TFTP_ROOT

./templates

Here you can place configuration that is templated.

Basic functionality is to take whatever you put in the environment of container will be replaced in the templates. For example if you provide an environment variable of HOST_IP=127.0.0.1 then every instance of the word HOST_IP in your templates will be replaced with this string.

VAR	default	info
INTERFACE	eth0	the dnsmasq interface
HOST_IP	127.0.0.1	host ip address
DNS1	1.1.1.1	DNS server 1
DNS2	8.8.8.8	DNS server 2
REV_CIDR	127.0.0.0/24	reverse look up cidr for consul
DHCP	false	enable dhcp server
TFTP	false	enable tftp server

./config

The config directory is used to view current running config and make on the fly alterations if you need and reload dnsmasq from the container. Its just the configuration directory mounted on the host(-v ${PWD}/config:/etc/dnsmasq.d or ./config:/etc/dnsmasq.d).

./tftp

You can put files here, and in the config.yml set the tftp options. Be sure that you mount the volume -v ${PWD}/tftp:/srv/tftp or ./tftp:/srv/tftp in compose, and that this volume matches the tftp.root key in config.yml

tftp:
  range:
    - 10.0.15.20
    - 10.0.15.200
  host: 10.0.15.138
  domain: 7ds.xyz
  root: /srv/tftp

use - docker commands

See configure section on configuring.
Then evaluate these commands and the expressions below:

• make build - build container
• make run - run the container detached
• make exec - enter(👀) the container
• make test.alpine - run an alpine container as a control to see if it can do what we want it to do (dig @127.0.0.1 google.com - provide dns from localhost)
• make test.dnsmasqpxe - run our container to see if it can do what we want it to do (dig @127.0.0.1 google.com - provide dns from localhost)
• make test - do both the tests and clean up after
• make clean - stop and remove containers

# build container
docker build --no-cache -t dnsmasqpxe -f .docker/Dockerfile .
# run container
docker run -d -v ${PWD}/config/:/etc/dnsmasq.d/ -v ${PWD}/templates/:/tmp/templates/ --name dnsmasqpxe dnsmasqpxe
# test if a normal alpine can do what we want to accomplish
# (hint: it should time out)
docker container run alpine /bin/ash -c "apk add bind-tools && dig -p 53 @127.0.0.1 google.com"
# test if we can do it with our container
# (hint: should be a #successbaby.gif)
docker container run -d -v ${PWD}/config/:/etc/dnsmasq.d/ -v ${PWD}/templates/:/tmp/templates/ --name dnsmasqpxe trailmix/dnsmasqpxe && docker exec -it dnsmasqpxe /bin/ash -c "apk add bind-tools && dig -p 53 @127.0.0.1 google.com"
# enter the container (👀)
docker exec -it dnsmasqpxe /bin/bash

port alterations

• you can alter the port, for example 1000:53/udp will make the host listen on port 1000 and forward it to 53 on the container.