Sunday, 9 June 2019

Manage docker image in Ansible using docker_image module



Build docker image using Ansible


Docker as you know is the most popular containerization platform and Ansible is the leading automation tool. In this post we will see how we can automate / manage docker images with Ansible.

Module:

Ansible provides docker_image module to pull / create docker image.

We will cover two areas of docker image
(a) Pulling images from repository using Ansible
(b) Creating images from dockerfile using Ansible

Pulling images from repository using Ansible:

Lets see how we can pull docker image by using docker_image module. Here I am pulling RabbitMQ image.

Source Code:



[root@test ansible_example]# cat docker-pull.yml

---

- hosts: localhost

  tasks:

  - name: Pull RabbitMQ Image

    docker_image:

      name: rabbitmq

      source: pull



Lets run the above playbook.

Output:




[root@test ansible_example]# ansible-playbook docker-pull.yml



 [WARNING]: Could not match supplied host pattern, ignoring: all



 [WARNING]: provided hosts list is empty, only localhost is available



PLAY [localhost] ***************************************************************************************************************



TASK [Gathering Facts] *********************************************************************************************************



ok: [localhost]



TASK [Pull RabbitMQ Image] *******************************************************************************************************



changed: [localhost]



PLAY RECAP *********************************************************************************************************************



localhost                  : ok=2    changed=1    unreachable=0    failed=0






Explanation:

This will download RabbitMQ image from docker repository. To verify use "docker images" command and we will find RabbitMQ images has been pulled from docker images.

Creating images from dockerfile using Ansible:

Docker provides another way to create images using dockerfile. Ansible also provides way to automate creating docker images using dockerfile.

Creating dockerfile:


FROM ubuntu

RUN apt-get update

RUN apt-get install -y rabbitmq-server



Now lets create playbook to build docker my rabbitmq image from above dockerfile

Source Code:




[root@test ansible_example]# cat docker-build.yml

---

- hosts: localhost

  tasks:

  - name: Build RabbitMQ image

    docker_image:

      path: .

      name: test/my-rabbitmq

      tag: v1

      source: build


In the above code snippet, we are trying to build a docker image located at current path.

Now lets run the playbook.



[root@test ansible_example]# ansible-playbook docker-build.yml



 [WARNING]: Could not match supplied host pattern, ignoring: all



 [WARNING]: provided hosts list is empty, only localhost is available



PLAY [localhost] ***************************************************************************************************************



TASK [Gathering Facts] *********************************************************************************************************



ok: [localhost]



TASK [Build RabbitMQ image] *******************************************************************************************************



changed: [localhost]



PLAY RECAP *********************************************************************************************************************



localhost                  : ok=2    changed=1    unreachable=0    failed=0


Please note you can easily push the local image to repository using Ansible. Here is the playbook example:




[root@test ansible_example]# cat docker-push.yml

---

- hosts: localhost

  tasks:

  - name: Push image

    docker_image:

   name: test/rabbitmq:v1

   repository: localhost:4800/test

   tag: v1

   push: yes

   source: local


Conclusion and Best practices:

Basically you can replace your docker-compose yml file with Ansible easily to manage containers even better. This way you can automate containerized application creation & deployment at one place and when the build triggers and completes, Ansible playbook can automatically deploy containers from one place to multiple node(s)

If you are looking for all the options of  docker_image module, please visit the official link here

Kubernetes is Docker orchestration engine and most devops team uses Kubernetes for docker lifecycle. This article can be helpful if you are looking for large number of container deployment using Ansible and Kubernetes.

That's all for building / managing docker images using Ansible. If you have any query, please mention in comment section. Thanks

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