Docker is a software container platform that allows you to package up an application with all its dependencies and requisite libraries into a self-reliant module. It moves the architecture design center of gravity from host/VM to containerized applications. Containers help eliminate the risk of incompatibilities or version conflicts between the application and the underlying OS. Furthermore, they can easily be migrated across any machine running Docker.

As it relates to cloud-native applications, containers are an effective way to package applications for runtime, great for version management, and efficient in operating deployments. Docker is a leading solution in this space, and its Community Edition (CE) is free to use.

In addition to Docker, there are several noteworthy open source projects that can help maximize the use of Docker and help create cloud-native systems:

• Infrakit is a toolkit for infrastructure orchestration. It emphasizes the immutable architecture approach, and breaks down automation and management processes into small components. Infrakit provides infrastructure support for higher-level container orchestration systems and makes your infrastructure self-healing. It has many plugins to other popular tools and projects, such as Swarm, Kubernetes, Terraform, and Vagrant, and supports AWS, Google, and VMWare environments (https://github.com/docker/infrakit).
• Docker Swarm(kit) is a cluster management and orchestration tool for Docker Engine 1.12 and later. It allows your Docker container deployment to support service reconciliation, load balancing, service discovery, and built-in certification rotation. Docker Swarm standalone is also available, but has seen its active development cease as Swarmkit has surged in popularity (https://github.com/docker/swarmkit).
• Portainer is a lightweight management UI for Docker environments. It's simple to use and runs on a single container that can run on any Docker engine. When building an operational control pane, UIs such as Portainer are indispensable in pulling together a master view of the environment and systems. (Go to https://github.com/portainer/portainer and https://portainer.io/ to learn more).