Introduction

This project is based on the work of LMtx (https://github.com/LMtx/ansible-lab-docker.git). Here the changes:

upgraded to ansible 2.9
switched base image from Ubuntu to Centos 8 with systemd
removed ssh-agent and password protection for ssh key
added ansible.cfg in lab directory for custom configuration and inventory
created all-in-one Vagrant machine (centos8 + docker + containers) for users can't install docker
added port-forward to access master01 container directly from the host (root@localhost:1022)
added "screen" (teminal multiplexer) to have an overview of all four "servers" from a single terminal window
added port-forward to access host01, host02 and host03 containers on port 80 directly from the host (http://localhost:8001, 8002 and 8003)
added examples and exercises

The aim of this guide is setup of Ansible training environment using Docker containers. After finishing this tutorial you will have Docker master container that can manage three host containers (you can easily extend number of managed hosts to meet your needs).

Why I decided to use Docker instead of conventional virtualization like VirtualBox? Docker containers consume much less resources so you can build bigger test environments on your laptop. Docker container is way faster to start/kill than standard virtual machine which is important when you experiment and bring the whole environment up and down. I used Docker Compose to automate setup of lab environment (there is no need to maintain each container separately).

This Ansible lab is composed of four containers:

master01
host01
host02
host03

IMPORTANT: In order to follow this tutorial you need to install Docker or Vagrant on your host machine.

Quick start

Linux requirements

docker
docker-compose
git (optional, you can download the zip file of this repository)

It is not necessary but if you prefer run docker inside a VM install libvirt (or virtualbox) and vagrant.

Windows requirements

virtualbox
vagrant
git (optional, you can download the zip file of this repository)
putty (optional, you can use any ssh client for Windows)

Clone repository

Clone this git repository:

git clone https://github.com/camandel/ansible-lab-docker.git

or download and extract the zip file.

Build images and run containers

If you are on a Linux server with docker already installed enter directory containing docker-compose.yml file and build docker images and run containers in the background (details defined in docker-compose.yml):

docker-compose up -d

Run a Vagrant machine

If you need a VM to run the lab install Vagrant and your hypervisor (tested with virtualbox and libvirt) and run:

vagrant up
vagrant ssh

Connect to master node (master01):

From the docker host run:

docker exec -it master01 bash

or from the host running Vagrant machine:

vagrant ssh
vagrant@ansible-lab $ sudo docker exec -it master01 bash`

or connect direcly from your host to master01 container (it exposes host:2022 to container:22 and Vagrant forwards host:2022 to guest:2022):

ssh root@localhost -p 2022 # password is ansiblelab

here you can start "screen" to have four windows already opened on master01, host01, host02 and host03 (F11 or F12 to switch from one window to another or use standard screen commands such as CTRL+a+n, CTRL+a+p):

screen

Verify if network connection is working between master and managed hosts:

ping -c 2 host01

then verifify is master can connect to all managed hosts with an ansible ad-hoc command:

ansible -m ping all

If you don't use "screen" open other ssh sessions to host01, host02 and host03 and run the check from master01:

cd /opt/ansible-lab
ansible -m ping all

To play with http services these port-forwarding have been activated:

localhost:8001 -> host01:80
localhost:8002 -> host02:80   
localhost:8003 -> host03:80

Ansible playbooks

Run a sample ansible playbook that checks connection between master node and managed hosts:

ansible-playbook -i examples/inventory ping_all.yml

Copy data between local file system and containers

Copy directory from container to local file system

docker cp master01:/opt/ansible-lab/ .

Copy directory from local file system to container:

docker cp ./demo.yml master01:/opt/ansible-lab/examples/

You can check usage executing:

docker cp --help

Cleanup

After you are done with your experiments or want to destroy lab environment to bring new one execute following commands.

Stop containers:

docker-compose kill

Remove containers:

docker-compose rm

Remove volume:

docker volume rm ansible_ansible_vol

If you want you can remove Docker images (although that is not required to start new lab environment):

docker rmi ansible_host ansible_master ansible_base

Tips

In order to share public SSH key between master and host containers I used Docker volume mounted to all containers:

docker-compose.yml:

[...]
volumes:
  - ansible_vol:/opt/ansible-lab
[...]

Master container stores SSH key in that volume (ansible/master/Dockerfile):

[...]
WORKDIR /var/ans
RUN ssh-keygen -t rsa -C "master key" -f master_key
[...]

And host containers add SSH public key to authorized_keys file (host/run.sh) in order to allow connections from master:

cat /opt/ansible-lab/master_key.pub >> /root/.ssh/authorized_keys

IMPORTANT: this is valid setup for lab environment but for production deployment you have to distribute the public key other way.

Troubleshooting

Host containers stop after creation

Check that hosts/run.sh has proper end of line type - it should be Linux/Unix (LF) not Windows (CRLF). You can change end of line type using source code editor (like Notepad++ or Visual Studio Code); under Linux you can use dos2unix command.

Other issue

Please open an issue and I'll try to help.