Crossplane Fundamentals
Crossplane is a Kubernetes add-on that lets you provision and manage cloud infrastructure using Kubernetes-style declarative YAML. It extends the Kubernetes API with custom resources representing cloud services, enabling platform teams to offer self-service infrastructure through familiar kubectl workflows.
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Don't Panic
Don't Panic - Crossplane Fundamentals
Crossplane Fundamentals centers on Crossplane. Crossplane is a framework for building control planes on Kubernetes. A control plane exposes an API, accepts a desired state, and keeps the systems behind that API aligned with the request.
Operate from the project's own resources and APIs. Learn how desired state becomes running state, which status conditions matter, and which dependencies (network, storage, identity, certificates) the control plane assumes.
Upgrades, backups, and credential rotation are part of the product, not optional aftercare. Version skew between clients and servers creates failures that look like application bugs. Pin versions and rehearse rollback.
Convenience features reduce boilerplate and widen blast radius. Enable them when you can observe and reverse the expanded surface. Defaults from quickstarts are starting points, not production policy.
Name owners for upgrades, credentials, and disaster recovery before traffic arrives. Unowned control-plane state becomes an outage with no clear pager. Prefer explicit version pins and tested rollback over floating tags that quietly change behavior between deploys.
Name owners for upgrades, credentials, and disaster recovery before traffic arrives. Unowned control-plane state becomes an outage with no clear pager. Prefer explicit version pins and tested rollback over floating tags that quietly change behavior between deploys.
Name owners for upgrades, credentials, and disaster recovery before traffic arrives. Unowned control-plane state becomes an outage with no clear pager. Prefer explicit version pins and tested rollback over floating tags that quietly change behavior between deploys.
Read the Intro for the mental model. Use the Cheatsheet when you need the resource map. Updates and Upstream track the Crossplane release line that changes these APIs.
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Sources
- https://docs.crossplane.io/latest/whats-crossplane/
Supports
- Crossplane as a control plane framework for platform engineering built on Kubernetes
- Desired-state control planes, lifecycle monitoring, and drift correction
- Four components: Composition, managed resources, Operations, and package manager
- Composition Function pipeline mental model and example App resource graph
- Managed resources as ready-made Kubernetes custom resources
- Operation, CronOperation, and WatchOperation modes and alpha status
- Package manager installation and reuse goals
- https://docs.crossplane.io/latest/whats-new/
Supports
- Namespaced XRs and managed resources in Crossplane v2
- Namespaced XRD default scope and cluster scope alternative
- Composition of any Kubernetes resource
- Legacy v1 compatibility and migration cautions
- Native patch and transform removal in favor of Composition Functions
- https://docs.crossplane.io/latest/get-started/install/
Supports
- Crossplane installation into an existing Kubernetes cluster with Helm
- Crossplane system namespace and installed components
- Provider, Function, and Configuration resources enabled after installation
- https://docs.crossplane.io/latest/managed-resources/managed-resources/
Supports
- Managed resource and external resource distinction
- Provider mapping of external services to managed resources
- forProvider as desired external configuration and source of truth by default
- atProvider as observed external state
- Direct use of managed resources
- https://docs.crossplane.io/latest/packages/providers/
Supports
- Providers as external API integrations with authentication, API calls, and controller logic
- Provider installation, pod behavior, health, configuration, and package revisions
- Continuous reconciliation of managed resources with external resources
- Digest pinning and revision activation options
- https://docs.crossplane.io/latest/composition/composite-resource-definitions/
Supports
- XRD as a custom API schema and XR as an instance of that API
- XRD names, versions, schema, and scope
- Namespaced, Cluster, and LegacyCluster scope behavior
- https://docs.crossplane.io/latest/composition/composite-resources/
Supports
- XR as a single Kubernetes object representing a set of resources
- Requirement for an XRD and Composition
- XRD and Composition roles in creating a custom API
- https://docs.crossplane.io/latest/composition/compositions/
Supports
- Composition type matching and ordered Function pipelines
- Function input, observed state, desired state, and returned resource behavior
- Composed resources as any Kubernetes resource
- Crossplane service account access and RBAC requirement for other resource kinds
- Local rendering command, Docker requirement, and YAML output
- https://docs.crossplane.io/latest/composition/composition-revisions/
Supports
- Immutable Composition revisions created for Composition changes
- Revision selection and update controls for composite resources
- https://docs.crossplane.io/latest/packages/functions/
Supports
- Functions as packages that extend Composition behavior
- Function installation through a Function package object
- https://docs.crossplane.io/latest/packages/configurations/
Supports
- Configuration packages as portable collections of Crossplane resources
- Packaging of XRDs, Compositions, and dependencies for reuse
- https://docs.crossplane.io/latest/operations/
Supports
- Operations as alpha in Crossplane v2
- Once, scheduled, and resource-change task modes
- https://github.com/crossplane/crossplane
Supports
- Crossplane v2.3 as the current maintained release on the verification date
- Crossplane project release support schedule