When people talk about containers, they usually mean application containers. Docker is automatically associated with application containers and is widely used to package applications and services. But there is another type of container: system containers. Let us look at the differences between application containers vs. system containers and see how each type of container is used:
Application containers are used to package applications without launching a virtual machine for each app or each service within an app. They are especially beneficial when making the move to a microservices architecture, as they allow you to create a separate container for each application component and provide greater control, security and process restriction. Ultimately, what you get from application containers is easier distribution. The risks of inconsistency, unreliability and compatibility issues are reduced significantly if an application is placed and shipped inside a container.
Docker is currently the most widely adopted container service provider with a focus on application containers. However, there are other container technologies like CoreOS’s Rocket. Rocket promises better security, portability and flexibility of image sharing. Docker already enjoys the advantage of mass adoption, and Rocket might just be too late to the container party. Even with its differences, Docker is still the unofficial standard for application containers today.
Docker Datacenter enables the deployment of containerized apps across multiple environments, from on-premises to virtual private cloud infrastructure.
With Docker Datacenter you can provide a Containers as a Service (CaaS) environment for your teams.
Deploying Docker Datacenter provides options for container deployment:
As the use of containers increases and organizations deploy them more widely, the need for tools to manage containers across the infrastructure also increases. Orchestrating a cluster of containers is a competitive and rapidly evolving area, and many tools exist offering various feature sets.
Container orchestration tools can be broadly defined as providing an enterprise-level framework for integrating and managing containers at scale. Such tools aim to simplify container management and provide a framework not only for defining initial container deployment but also for managing multiple containers as one entity -- for purposes of availability, scaling, and networking.
Some container orchestration tools to know about include:
Additionally, the Cloud Native Computing Foundation (CNCF) is focused on integrating the orchestration layer of the container ecosystem. The CNCF’s stated goal is to create and drive adoption of a new set of common container technologies, and it recently selected Google’s Kubernetes container orchestration tool as its first containerization technology.
System containers play a similar role to virtual machines, as they share the kernel of the host operating system and provide user space isolation. However, system containers do not use hypervisors. (Any container that runs an OS is a system container.) They also allow you to install different libraries, languages, and databases. Services running in each container use resources that are assigned to just that container.
System containers let you run multiple processes at the same time, all under the same OS and not a separate guest OS. This lowers the performance impact, and provides the benefits of VMs, like running multiple processes, along with the new benefits of containers like better portability and quick startup times.