How to contribute

This section is the local, code-level guide for contributing to containerd/containerd. It complements the upstream contributor docs at containerd/project (see https://github.com/containerd/project/blob/main/CONTRIBUTING.md) and the repo's own CONTRIBUTING.md.

At a glance

1. Fork → branch → develop → make check binaries test → PR.
2. Keep the package layout rules in CONTRIBUTING.md in mind: no source files in the repo root, and use the right top-level directory (core, plugins, pkg, internal, client, cmd, api, docs).
3. PRs must be opened by humans. Any AI-assisted authorship must be reviewed by the human author before submission (see CONTRIBUTING.md).
4. Follow the DCO rules from containerd/project: every commit needs Signed-off-by:.

Pages in this section

• Development workflow
• Testing
• Debugging
• Patterns and conventions
• Tooling

Where each kind of code goes

From CONTRIBUTING.md and the actual layout of the v2 tree:

Directory	What belongs here
api/	Protobuf service and message definitions, generated .pb.go/_grpc.pb.go/_ttrpc.pb.go files
client/	The Go client used by ctr, third-party programs, and the CRI plugin in-process
cmd/	main packages and code only used by a single command
contrib/	External tooling and example shims (snapshot service helpers, ansible, fuzz drivers, …)
core/	Core interface definitions and the most important built-in implementations
defaults/	Per-OS default constants (paths, addresses)
docs/	Markdown documentation
internal/	Daemon-internal packages, not for external import (e.g. internal/cri)
pkg/	Reusable helpers usable by clients (oci, archive, namespaces, ioutil, sys, …)
plugins/	Built-in plugins registered via init()
script/	CI and dev-loop helper scripts
version/	The exported version string (populated by -ldflags from the Makefile)

Conventions enforced by tooling

• make check runs golangci-lint with the rules in .golangci.yml.
• make check-protos verifies that any .proto change has been re-generated (make protos). This requires protoc and buf.
• buf format --diff --exit-code enforces protobuf formatting.
• The lychee link checker runs on docs (.lycheeignore configures exclusions).