Docker is a software platform that allows you to create, manage and execute isolated applications in containers. A container is nothing more than a methodology for creating software packages in a format that allows it to be run independently and isolated on a shared operating system. Unlike the virtual machine containers do not include a complete operating system, but only the libraries and settings needed to run the software. Therefore there are a series of advantages in terms of size, speed, portability and resource management.
- Figure 1 – Diagram of containers
In the world of Microsoft Azure there are different configuration and use possibilities about Docker containers that I list synthetically:
- VM Extension: through a specific Extension you can implement Docker inside a virtual machine.
- Azure Container Service: deploys quickly into a cluster environment Azure Docker Swarm, DC/OS or Kubernetes ready for production. This is the most complete solution for the orchestration of containers.
- Docker EE for Azure: is a template available on the Azure Marketplace, a collaboration between Microsoft and Docker, which makes it possible to provision a clustered Docker Enterprise Edition integration with Azure VM Scale Sets, the Azure Load balancers and the Azure Storage.
- Rancheros: is a Linux distribution designed to run containers available as template within the Marketplace Azure Docker.
- Web App for Containers: you have the option of using containers, making the deployment in the Azure App Service managed platform as a Web App running in a Linux environment.
- Azure Container Instances (currently in preview): is definitely the easiest and quickest way to run a container Docker in the Azure platform, without the need to create virtual machines, ideal in scenarios where containers blocks.
- Azure Service Fabric: supports the containers in both the Windows and Linux. The platform contains natively support for Docker Wrote (currently in preview), allowing you to orchestrate applications based on containers in the Azure Service Fabric.
- DC/OS on Azure: This is a managed cloud service that provides an environment for the deployment of workloads in cluster using DC/OS platform (Datacenter Operating System).
All these possibilities enable, according to the needs and to the scenario that you must implement, choosing the most appropriate deployment methodology in the container for execution environment Azure Docker.
In this article we will create a Docker environment in a Virtual Machine using the Docker Extension. Starting from a virtual machine in Azure, you can add the Docker Extension which installs and configures the daemon Docker, the client Docker and Docker Wrote.
This extension is supported for the following Linux distributions:
- Ubuntu 13 or higher.
- CentOS 7.1 or higher.
- Red Hat Enterprise Linux (RHEL) 7.1 or higher.
- CoreOS 899 or higher.
Adding the extension from the Azure Portal can be done via the following steps. The section Extensions Select the virtual machine button Add:
- Figure 2 – Adding Extensions to the VM from the Azure Portal
Then shows the list of Extensions available, you stand onExtension Docker and press the button Create.
- Figure 3 – Selection of Extension Docker
To enable secure communication with the Docker system implemented in your Azure environment you should use certificates and keys issued by a trusted CA. If you do not have a CA to generate these certificates you can follow the instructions in section Create a CA, Server and client keys with OpenSSL present in the official documentation of Docker.
- Figure 4 – Communication scheme docker by encrypted protocol TLS
The Extension wizard requires first to enter the communications port of the Engine Docker (2376 is the default port). Also the CA's certificate is requested, your Server certificate and Server Key, in base64-encoded format:
- Figure 5 – Parameters required by the wizard to add the Docker VM Extension
Adding the Extension Docker takes several minutes at the end of which the virtual machine will be installing the latest stable version of Docker Engine and daemon Docker will listen on the specified port using certificates entered in the wizard.
- Figure 6 – Details of the Extension Docker
In case you need to allow Docker communication from outside the vNet where is attested the VM with Docker you must configure appropriate rules in Network Security Group used:
- Figure 7 – Configuration example NSG to allow communication Docker (door 2376)
At this point the Docker environment is ready to be used and from a remote client you can start the communication:
- Figure 8 – Docker command run from a remote client to retrieve information
Conclusions
The Azure Docker VM extension is ideal to implement easily, in a reliably and securely mode, a dev or production Docker environment on a single virtual machine. Microsoft Azure offers a wide range of possibilities in the choice of implementation related to the Docker platform, with a lot of flexibility by letting you choose the most appropriate solution for your needs.
