Containerd is a core container runtime that is used by Kubernetes, Docker, and other projects. It provides a stable runtime for container-related components and services. It has a discrete architecture with decoupled services like containers, images, and tasks that are exposed via gRPC. The document then provides examples of how to code a simple Containerd client to pull an image, create a container, and start the container task.

1. Embedding Containerd
(for fun and profit)
Phil Estes, IBM Cloud Architecture, Office of the CTO
@estesp
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2. @estesp
Why Containerd?
•“Boring,” stable core container runtime for the
ecosystem
•Useful for any higher layer container native
stack component (e.g. container orchestrator)
• Used by Kubernetes incubator CRI (containerd-cri)
• Used by Docker engine (17.12 CE and above)
•Move governance from BDFL to TSC
• Moby TSC formed and in place; governance docs
updated
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runc
containerd

3. @estesp
Who Uses Containerd?
•cri-containerd
• Implements the CRI for containerd daemon
•LinuxKit
• Core container runtime for minimal, secure Linux OS assembler
• BuildKit
• Highly efficient container image builder; can use containerd directly
•Docker engine/Swarm
• containerd 1.0 takes the place of minimal containerd 0.2.x implementation
for 17.12 and above
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4. @estesp
Containerd Architecture
• Discrete, decoupled
services exposed via
gRPC
• Use known good
technology
• OCI runtime/image
• gRPC
• Prometheus
• Not opinionated
towards one platform
• Apply learnings from
runtime history
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Runtimes
Metadata
ContainersContent DiffSnapshot Tasks EventsImages
GRPC Metrics
Runtimes
Storage
OS

5. @estesp
Containerd API
•Guiding principles:
• Simplicity/Clarity
• Stability (gRPC/protobuf
versioned)
•Pass through model: API objects
are lightweight metadata
• doesn’t attempt to abstract
existing specs (OCI)
•GoDoc published (see resources)
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6. @estesp
Containerd Client Example
An example containerd client application
https://github.com/estesp/examplectr
•Let’s code a simple client using the Go client library to:
• connect to the containerd daemon
• pull an image
• create a container
• start the container (task)
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7. @estesp
Containerd Advanced Example
•Let’s add some more concepts to our containerd client example:
• User namespaces
• (Bind) Mounting from the host
• Optional custom command
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8. @estesp
Thank You!
•Containerd Project: https://github.com/containerd/containerd
•Getting Started Guide:
https://github.com/containerd/containerd/blob/master/docs/getti
ng-started.md
•GoDoc: https://godoc.org/github.com/containerd/containerd
•Website: https://containerd.io
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Resources
API Users
• CRI-Containerd: https://github.com/containerd/containerd
• Bucketbench: https://github.com/estesp/bucketbench
• Moby project engine: https://github.com/moby/moby/tree/master/libcontainerd