Wednesday, April 10, 2019

Create a mini lab for practicing ansible using docker

To practice ansible, you need to have at least 2 machines. I suggest using containers rather than VM, since containers can be quickly spawned, and are light on the resources.


First, make sure you have docker Community Edition installed. If not, follow the install guide here.

Check your docker version
# docker version

Start the docker engine
# sudo systemctl start docker 

In this exercise, we will use ubuntu as our base operating system. So, run a container using the ubuntu image from docker hub. The options are -i for interactive, -t to allocate pseudo TTY and -d to run the container in the background
# docker run -it -d --name="ansible-master" ubuntu

The ubuntu image does not come with ssh, which is needed for ansible, so we need to install that, together with vim text editor 
# docker exec -it apt update; apt install vim openssh-server -y

Change the root password
# docker exec -it ansible-master passwd 

Permit root login for ssh
# docker exec -it ansible-master /bin/bash
ansible-master: # cat >> /etc/ssh/sshd_config <<EOF
PermitRootLogin yes
EOF

Start ssh
ansible-master: # service ssh start; exit

Create an image based on ansible-master. This image will be used later to create ansible-client1 container
# docker commit -m "ubuntu with vim and openssh-server" myubuntu:2019041001

Run a container called ansible-client1 from the image created above
# docker image ls
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
myubuntu            2019041001          17f43a3ef384        10 minutes ago      265MB
# docker run -d -it --name="ansible-client1" myubuntu:2019041001

Start ssh service on ansible-client1
# docker exec -it ansible-client1 service ssh start

Try to ssh into both machines. Get the ip address of the containers using "docker inspect" command
# docker inspect ansible-client1 | grep -w IPAddress
            "IPAddress": "172.17.0.3",
                    "IPAddress": "172.17.0.3",
# docker inspect ansible-master | grep -w IPAddress
            "IPAddress": "172.17.0.2",
                    "IPAddress": "172.17.0.2",
# ssh root@172.17.0.2
# ssh root@172.17.0.3

Install ansible on ansible-master
# docker exec -it ansible-master apt install ansible -y

Check ansible version
# docker exec -it ansible --version

Create ssh-key without password
# docker exec -it ssh-keygen

Transfer the key to ansible-client1
# docker exec -it ssh-copy-id 172.17.0.3

Edit /etc/ansible/hosts to include all nodes
# docker exec -it ansible-master /bin/bash
ansible-master: # cat >> /etc/ansible/hosts <<EOF
localhost
ansible-client1 ansible_host=172.17.0.3

[all]
localhost
ansible-client1
EOF


Test ansible using ping module
# docker exec -it ansible-master -m ping all
localhost | SUCCESS => {
    "changed": false, 
    "ping": "pong"
}
ansible-client1 | SUCCESS => {
    "changed": false, 
    "ping": "pong"
}

Congratulations, now you have your own mini ansible lab, using docker. You can add more clients as you wish later.

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