OCI, CRI, ??: Making Sense of the Container Runtime Landscape in Kubernetes - Phil Estes, IBM

Summary

The speaker discusses the evolution and standardization of container runtimes, emphasizing the importance of the Open Container Initiative (OCI) in creating a common ground for various runtimes and images. They highlight Docker's impact on popularizing containers but also note the emergence of alternatives like ContainerD, CRI-O, and rkt. The talk delves into Kubernetes' reliance on the Container Runtime Interface (CRI) for container management, showcasing how different runtimes can integrate with Kubernetes. The speaker also touches on ongoing work within the OCI, such as image signing and the potential for further standardization, aiming to simplify choices for developers and operators.

Takeaways

• 📚 The presentation aims to clarify the evolution of container runtimes and demystify terms like OCI and CRI.
• 💡 Docker popularized container usage with simple commands that made it easy to run services like Redis or Nginx in milliseconds.
• 🚀 Docker is not the only container runtime; alternatives like rkt, Cloud Foundry, LXE, lxd, singularity, and more have been developed for various use cases.
• 🔗 The Open Container Initiative (OCI) was created to standardize container runtimes and image formats, ensuring interoperability among different tools.
• 📈 The OCI has led to the development of the runtime-spec and runc, which are widely recognized and used in the industry.
• 🛠 The Container Runtime Interface (CRI) was introduced to allow Kubernetes to work with any container runtime that implements the CRI API.
• 🔄 Kubernetes itself does not run containers; it relies on a container runtime to manage the execution of containers.
• 🔄 Different runtimes like Docker, containerd, and CRI-O are implementing the CRI to work with Kubernetes.
• 👥 The industry is moving towards more standardization in areas like artifacts, image signing, and distribution specs within the OCI.
• 🔒 There is a growing interest in enhanced container isolation and security, with projects like gVisor and Kata Containers gaining attention.
• 🔄 CRI-O and containerd are becoming more popular as default runtimes in Kubernetes environments, especially in managed services and cloud platforms.

Q & A

What was the main goal of the talk on container runtimes?

The main goal was to help the audience understand the current state of container runtimes, demystify terms like OCI and CRI, and provide informative content on the topic in an engaging way.

What is the significance of Docker's introduction in 2014-2015?

Docker's introduction was significant because it brought simplicity and standardization to container usage with commands like 'docker run', making it easier for developers to deploy services quickly and efficiently.

Why did CoreOS develop Rocket as an alternative to Docker?

CoreOS developed Rocket as an alternative to Docker to offer new ideas and a different approach to connecting developers with the features of the Linux kernel, such as namespaces and cgroups.

What is the purpose of the Open Container Initiative (OCI)?

The purpose of the OCI is to create a common specification for container runtimes and image formats, allowing for interoperability among different tools and ensuring a consistent definition of what it means to have a container.

What does the Container Runtime Interface (CRI) provide for Kubernetes?

The CRI provides an abstraction layer for container runtimes, allowing Kubernetes to interact with different runtimes through a standardized API, thus enabling the orchestration of containers without being tied to a specific runtime.

Why was the CRI interface introduced in Kubernetes?

The CRI interface was introduced to simplify the integration of Kubernetes with various container runtimes, avoiding the need for multiple code bases and ensuring a consistent way to manage container operations.

What is the current state of container runtime usage in Kubernetes?

Docker remains the most commonly used runtime, but other runtimes like containerd, CRI-O, and others are gaining traction, especially as they become default options in managed Kubernetes services and meet the needs of different use cases.

What is the role of the Runtime Class in Kubernetes?

Runtime Class in Kubernetes allows users to specify which container runtime should be used for a particular pod, providing flexibility in choosing the right runtime for different workloads.

How does the talk address the topic of container security?

The talk touches on the topic of container security by mentioning the interest in image signing and the work being done around artifacts and standard media types, indicating a growing focus on securing containers in production environments.

What are some of the ongoing efforts within the OCI?

Ongoing efforts within the OCI include finalizing the distribution spec, standardizing image signing processes, and exploring new ideas for container images, such as OCI v2, which aims to address current challenges and user needs.