1/14/2024 0 Comments Docker container startup timeThe container runtime is the low-level component that creates and runs containers. The containerd daemon is a central aspect of the Kubernetes CRI that enables Kubernetes to interact with various container runtimes, such as runC and Kata Containers. Containerd manages the container environment and oversees execution. The Docker engine doesn't manage containers directly, but instead relies on a separate module or high-level daemon process - part of the Docker package - called containerd. Docker provides a command-line interface - the CLI, or "console" - named docker-cli that users wield to build images, create container registries, load images from container registries and then start and manage containers. A key part of the container engine is the UI. Docker provides a comprehensive platform for developers and systems administrators - such as DevOps users. A platform such as Docker installs on a server or development computer and includes all the tools and utilities needed to build and run containers. The container engine sits at the very top of the container stack. Running containers in the Docker environment requires four fundamental components: the Docker engine/interface, the underlying daemon, the runtime and the container itself. ![]() The relationship between engines, runtimes and standardized interfaces is illustrated in Figure 1. CRI-O turns Kubernetes into a container engine that supports runC and Kata Containers as container runtimes for Kubernetes pods - though any OCI-compliant runtime should work. The Kubernetes Container Runtime Interface (CRI) provides an API that connects Kubernetes to container runtimes.ĬRI-O is an implementation of CRI which enables Kubernetes to use any OCI-compatible runtimes - rather than using Docker as the runtime for Kubernetes. ![]() This means Kubernetes must handle an array of container image formats - especially when creating and managing pods and clusters. OCI uses runC, which other engines, such as Docker and CRI-O, can also use - enabling greater container compatibility across container engines.Ĭontainers put an enormous value on orchestration, relying on vital tools like Kubernetes to automate and manage containerized applications and environments within the local data center, as well as in the cloud. This leads to refined and reliable container runtime tools.Īlthough there are several container image formats, the Open Container Initiative (OCI) has emerged as a popular and accepted standard for container images and runtimes. Standards streamline the methodology used to mount and run container images as containers. By applying standards to container image formats and associated metadata, the container industry can develop images and tools that are more refined, secure and interoperable. Standardization is an important part of container technology. The most common runtime is runC, but other container runtimes include crun, railcar and Kata Containers. For an OS such as Red Hat Enterprise Linux, the runtime would set up cgroups, set SELinux policy, set AppArmor rules and so on. Finally, it calls and hands off the container to a container runtime to start and manage the container's deployment.Ī container runtime is a low-level component of a container engine that mounts the container and works with the OS kernel to start and support the containerization process. ![]() The engine takes user input, interacts with a container orchestrator, loads the container image file (from a repository, usually stored in a cloud service, either public or private) and prepares storage to run the container. Typical container engines include Docker, CRI-O, RKT and LXD. A container engine is a general software platform that supports container use. VMs are completely isolated entities, however, whereas containers share the underlying OS kernel, which enables containers to be far smaller, faster and exist in greater numbers on a computer compared to traditional VMs.Ĭontainers require a container engine. This improves the computer's resource utilization and saves money - because more computing work can be performed on fewer servers. As with most VMs, multiple containers can exist on the same physical computer. What are containers, container engines and container runtimes?Ī container is a special type of virtual machine. Let's take a closer look at the roles and relationships of containers, engines and runtimes, and consider some of the implications involved. But the decision can have important consequences for the enterprise. There are several container runtimes available today, and the choice of runtime is often governed by the choice of container engine.
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