The workflow starts with:

• Attaining the docker image

If the docker image is present in Docker Hub or that kind of Docker REGISTRIES the images are selected from them. Developers can also create a great number of images if need be. Images have a layered architecture. Mostly a combination of a base layer and then a customised layer is used to create a docker image. There are several types of files that help to build images and they are kept in respective repositories. Some of the important files to consider to create docker images are docker files, docker-compose.yml files, etc. Multiple containers could be run together using docker-compose.yml files. Some of the types of repositories where the images are stored are

1. Version Control - This is used mainly used to store text-based files such as Dockerfiles, docker-compose.yml, and configuration files. Some of the version control systems are git, svn, Team Foundation Server, VSTS, and Clear Case.
2. Repository Manager - Large binary files such as that of Maven/Java, npm, NuGet, and RubyGems are stored in repository managers.Whereas smaller binary files could be saved to version control. Examples include NEXUS, Artifactory, and Archiva.
3. Package Repository - Packaged applications for example like an operating system such as CentOS, Ubuntu, and WINDOWS Server are stored in the package repository. Examples are yum, apt-get, and package management. They can also run several containers together described in a docker-compose.yml file and test the application.

• Deploy on UCP(Docker Universal control plane)

A CI/CD system runs unit tests, builds the applications, and create a  Docker image on the Docker Universal Control Plane (UCP). If the image passes all tests they are signed using Docker Content Trust and shipped to Docker Trusted Registry (DTR). The developer could also do testing on an INTEGRATION environment on UCP in cases where the developer’s machine does not have ACCESS to all the resources to run the entire application.

• Push Images

Once the image is ready newer images created are pushed into Docker Trusted Registry. The developer can use the command

The developer account in DTR is a must have to do this action

• Commit

Once the application is tested on UCP files used to create the application, its images, and its configuration is committed to version control. The commit triggers could be set up to trigger the CI/CD workflow. The images could now be used to create containers.