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 guide is not Ansible or Docker tutorial (although I explain some basic concepts). It's purpose is solely setup of lab environment to enable experiments with ansible on local machine.
IMPORTANT: In order to follow this tutorial you need to install Docker CE (Community Edition) on your machine. The installation is well documented at https://docs.docker.com/engine/installation/#supported-platforms and I will not cover it here.
A brief description of Ansible and Docker:
Ansible is IT automation system. It handles configuration-management, application deployment, cloud provisioning, ad-hoc task-execution, and multinode orchestration - including trivializing things like zero downtime rolling updates with load balancers.
You can read more at www.ansible.com
Docker is the world’s leading software container platform. Developers use Docker to eliminate "works on my machine" problems when collaborating on code with co-workers. Operators use Docker to run and manage apps side-by-side in isolated containers to get better compute density. Enterprises use Docker to build agile software delivery pipelines to ship new features faster, more securely and with confidence for both Linux, Windows Server, and Linux-on-mainframe apps.
You can read more at www.docker.com
Clone this git repository:
git clone https://github.com/LMtx/ansible-lab-docker.git
Enter ansible directory containing docker-compose.yml file.
Build docker images and run containers in the background (details defined in docker-compose.yml):
docker-compose up -d --build
Connect to master node:
docker exec -it master01 bash
Verify if network connection is working between master and managed hosts:
ping -c 2 host01
Start an SSH Agent on master node to handle SSH keys protected by passphrase:
ssh-agent bash
Load private key into SSH Agent in order to allow establishing connections without entering key passphrase every time:
ssh-add master_key
Enter passphrase for master_key:
As passphrase enter: 12345
Default key passphrase can be changed in ansible/master/Dockerfile
Run a sample ansible playbook that checks connection between master node and managed hosts:
ansible-playbook -i inventory ping_all.yml
Confirm every new host for SSH connections:
ECDSA key fingerprint is SHA256:HwEUUnBtOm9hVAR2PJflNdCVchSCzIlpOpqYlwp+w+w.
Are you sure you want to continue connecting (yes/no)?
Type: yes (three times)
Install PHP on web inventory group:
In order to group managed hosts for easier maintenance you can use groups in ansible inventory file.
Run a sample ansible playbook:
ansible-playbook -i inventory install_php.yml
docker cp master01:/var/ans/ .
docker cp ./ans master01:/var/
You can check usage executing:
docker cp --help
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
In order to share public SSH key between master and host containers I used Docker volume mounted to all containers:
[...]
volumes:
- ansible_vol:/var/ans
[...]
Master container stores SSH key in that volume (ansible/master/Dockerfile):
[...]
WORKDIR /var/ans
RUN ssh-keygen -t rsa -N 12345 -C "master key" -f master_key
[...]
And host containers add SSH public key to authorized_keys file (ansible/host/run.sh) in order to allow connections from master:
cat /var/ans/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.
Check that ansible/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.
Please open an issue and I'll try to help.