What’s in a basic project?

When scaffolding out a new project, Kubebuilder provides us with a few basic pieces of boilerplate.

Build Infrastructure

First up, basic infrastructure for building your project:

go.mod: A new Go module matching our project, with basic dependencies

module tutorial.kubebuilder.io/project

go 1.24.0

require (
	github.com/onsi/ginkgo/v2 v2.22.0
	github.com/onsi/gomega v1.36.1
	github.com/robfig/cron v1.2.0
	k8s.io/api v0.32.1
	k8s.io/apimachinery v0.32.1
	k8s.io/client-go v0.32.1
	sigs.k8s.io/controller-runtime v0.20.4
)

require (
	cel.dev/expr v0.18.0 // indirect
	github.com/antlr4-go/antlr/v4 v4.13.0 // indirect
	github.com/asaskevich/govalidator v0.0.0-20190424111038-f61b66f89f4a // indirect
	github.com/beorn7/perks v1.0.1 // indirect
	github.com/blang/semver/v4 v4.0.0 // indirect
	github.com/cenkalti/backoff/v4 v4.3.0 // indirect
	github.com/cespare/xxhash/v2 v2.3.0 // indirect
	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
	github.com/emicklei/go-restful/v3 v3.11.0 // indirect
	github.com/evanphx/json-patch/v5 v5.9.11 // indirect
	github.com/felixge/httpsnoop v1.0.4 // indirect
	github.com/fsnotify/fsnotify v1.7.0 // indirect
	github.com/fxamacker/cbor/v2 v2.7.0 // indirect
	github.com/go-logr/logr v1.4.2 // indirect
	github.com/go-logr/stdr v1.2.2 // indirect
	github.com/go-logr/zapr v1.3.0 // indirect
	github.com/go-openapi/jsonpointer v0.21.0 // indirect
	github.com/go-openapi/jsonreference v0.20.2 // indirect
	github.com/go-openapi/swag v0.23.0 // indirect
	github.com/go-task/slim-sprig/v3 v3.0.0 // indirect
	github.com/gogo/protobuf v1.3.2 // indirect
	github.com/golang/protobuf v1.5.4 // indirect
	github.com/google/btree v1.1.3 // indirect
	github.com/google/cel-go v0.22.0 // indirect
	github.com/google/gnostic-models v0.6.8 // indirect
	github.com/google/go-cmp v0.6.0 // indirect
	github.com/google/gofuzz v1.2.0 // indirect
	github.com/google/pprof v0.0.0-20241029153458-d1b30febd7db // indirect
	github.com/google/uuid v1.6.0 // indirect
	github.com/grpc-ecosystem/grpc-gateway/v2 v2.20.0 // indirect
	github.com/inconshreveable/mousetrap v1.1.0 // indirect
	github.com/josharian/intern v1.0.0 // indirect
	github.com/json-iterator/go v1.1.12 // indirect
	github.com/mailru/easyjson v0.7.7 // indirect
	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
	github.com/modern-go/reflect2 v1.0.2 // indirect
	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
	github.com/pkg/errors v0.9.1 // indirect
	github.com/prometheus/client_golang v1.19.1 // indirect
	github.com/prometheus/client_model v0.6.1 // indirect
	github.com/prometheus/common v0.55.0 // indirect
	github.com/prometheus/procfs v0.15.1 // indirect
	github.com/spf13/cobra v1.8.1 // indirect
	github.com/spf13/pflag v1.0.5 // indirect
	github.com/stoewer/go-strcase v1.3.0 // indirect
	github.com/x448/float16 v0.8.4 // indirect
	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.53.0 // indirect
	go.opentelemetry.io/otel v1.28.0 // indirect
	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.28.0 // indirect
	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc v1.27.0 // indirect
	go.opentelemetry.io/otel/metric v1.28.0 // indirect
	go.opentelemetry.io/otel/sdk v1.28.0 // indirect
	go.opentelemetry.io/otel/trace v1.28.0 // indirect
	go.opentelemetry.io/proto/otlp v1.3.1 // indirect
	go.uber.org/multierr v1.11.0 // indirect
	go.uber.org/zap v1.27.0 // indirect
	golang.org/x/exp v0.0.0-20240719175910-8a7402abbf56 // indirect
	golang.org/x/net v0.30.0 // indirect
	golang.org/x/oauth2 v0.23.0 // indirect
	golang.org/x/sync v0.8.0 // indirect
	golang.org/x/sys v0.26.0 // indirect
	golang.org/x/term v0.25.0 // indirect
	golang.org/x/text v0.19.0 // indirect
	golang.org/x/time v0.7.0 // indirect
	golang.org/x/tools v0.26.0 // indirect
	gomodules.xyz/jsonpatch/v2 v2.4.0 // indirect
	google.golang.org/genproto/googleapis/api v0.0.0-20240826202546-f6391c0de4c7 // indirect
	google.golang.org/genproto/googleapis/rpc v0.0.0-20240826202546-f6391c0de4c7 // indirect
	google.golang.org/grpc v1.65.0 // indirect
	google.golang.org/protobuf v1.35.1 // indirect
	gopkg.in/evanphx/json-patch.v4 v4.12.0 // indirect
	gopkg.in/inf.v0 v0.9.1 // indirect
	gopkg.in/yaml.v3 v3.0.1 // indirect
	k8s.io/apiextensions-apiserver v0.32.1 // indirect
	k8s.io/apiserver v0.32.1 // indirect
	k8s.io/component-base v0.32.1 // indirect
	k8s.io/klog/v2 v2.130.1 // indirect
	k8s.io/kube-openapi v0.0.0-20241105132330-32ad38e42d3f // indirect
	k8s.io/utils v0.0.0-20241104100929-3ea5e8cea738 // indirect
	sigs.k8s.io/apiserver-network-proxy/konnectivity-client v0.31.0 // indirect
	sigs.k8s.io/json v0.0.0-20241010143419-9aa6b5e7a4b3 // indirect
	sigs.k8s.io/structured-merge-diff/v4 v4.4.2 // indirect
	sigs.k8s.io/yaml v1.4.0 // indirect
)

Makefile: Make targets for building and deploying your controller

# Image URL to use all building/pushing image targets
IMG ?= controller:latest

# Get the currently used golang install path (in GOPATH/bin, unless GOBIN is set)
ifeq (,$(shell go env GOBIN))
GOBIN=$(shell go env GOPATH)/bin
else
GOBIN=$(shell go env GOBIN)
endif

# CONTAINER_TOOL defines the container tool to be used for building images.
# Be aware that the target commands are only tested with Docker which is
# scaffolded by default. However, you might want to replace it to use other
# tools. (i.e. podman)
CONTAINER_TOOL ?= docker

# Setting SHELL to bash allows bash commands to be executed by recipes.
# Options are set to exit when a recipe line exits non-zero or a piped command fails.
SHELL = /usr/bin/env bash -o pipefail
.SHELLFLAGS = -ec

.PHONY: all
all: build

##@ General

# The help target prints out all targets with their descriptions organized
# beneath their categories. The categories are represented by '##@' and the
# target descriptions by '##'. The awk command is responsible for reading the
# entire set of makefiles included in this invocation, looking for lines of the
# file as xyz: ## something, and then pretty-format the target and help. Then,
# if there's a line with ##@ something, that gets pretty-printed as a category.
# More info on the usage of ANSI control characters for terminal formatting:
# https://en.wikipedia.org/wiki/ANSI_escape_code#SGR_parameters
# More info on the awk command:
# http://linuxcommand.org/lc3_adv_awk.php

.PHONY: help
help: ## Display this help.
	@awk 'BEGIN {FS = ":.*##"; printf "\nUsage:\n  make \033[36m<target>\033[0m\n"} /^[a-zA-Z_0-9-]+:.*?##/ { printf "  \033[36m%-15s\033[0m %s\n", $$1, $$2 } /^##@/ { printf "\n\033[1m%s\033[0m\n", substr($$0, 5) } ' $(MAKEFILE_LIST)

##@ Development

.PHONY: manifests
manifests: controller-gen ## Generate WebhookConfiguration, ClusterRole and CustomResourceDefinition objects.
	# Note that the option maxDescLen=0 was added in the default scaffold in order to sort out the issue
	# Too long: must have at most 262144 bytes. By using kubectl apply to create / update resources an annotation
	# is created by K8s API to store the latest version of the resource ( kubectl.kubernetes.io/last-applied-configuration).
	# However, it has a size limit and if the CRD is too big with so many long descriptions as this one it will cause the failure.
	$(CONTROLLER_GEN) rbac:roleName=manager-role crd:maxDescLen=0 webhook paths="./..." output:crd:artifacts:config=config/crd/bases

.PHONY: generate
generate: controller-gen ## Generate code containing DeepCopy, DeepCopyInto, and DeepCopyObject method implementations.
	$(CONTROLLER_GEN) object:headerFile="hack/boilerplate.go.txt" paths="./..."

.PHONY: fmt
fmt: ## Run go fmt against code.
	go fmt ./...

.PHONY: vet
vet: ## Run go vet against code.
	go vet ./...

.PHONY: test
test: manifests generate fmt vet setup-envtest ## Run tests.
	KUBEBUILDER_ASSETS="$(shell $(ENVTEST) use $(ENVTEST_K8S_VERSION) --bin-dir $(LOCALBIN) -p path)" go test $$(go list ./... | grep -v /e2e) -coverprofile cover.out

# TODO(user): To use a different vendor for e2e tests, modify the setup under 'tests/e2e'.
# The default setup assumes Kind is pre-installed and builds/loads the Manager Docker image locally.
# CertManager is installed by default; skip with:
# - CERT_MANAGER_INSTALL_SKIP=true
KIND_CLUSTER ?= project-test-e2e

.PHONY: setup-test-e2e
setup-test-e2e: ## Set up a Kind cluster for e2e tests if it does not exist
	@command -v $(KIND) >/dev/null 2>&1 || { \
		echo "Kind is not installed. Please install Kind manually."; \
		exit 1; \
	}
	$(KIND) create cluster --name $(KIND_CLUSTER)

.PHONY: test-e2e
test-e2e: setup-test-e2e manifests generate fmt vet ## Run the e2e tests. Expected an isolated environment using Kind.
	KIND_CLUSTER=$(KIND_CLUSTER) go test ./test/e2e/ -v -ginkgo.v
	$(MAKE) cleanup-test-e2e

.PHONY: cleanup-test-e2e
cleanup-test-e2e: ## Tear down the Kind cluster used for e2e tests
	@$(KIND) delete cluster --name $(KIND_CLUSTER)

.PHONY: lint
lint: golangci-lint ## Run golangci-lint linter
	$(GOLANGCI_LINT) run

.PHONY: lint-fix
lint-fix: golangci-lint ## Run golangci-lint linter and perform fixes
	$(GOLANGCI_LINT) run --fix

.PHONY: lint-config
lint-config: golangci-lint ## Verify golangci-lint linter configuration
	$(GOLANGCI_LINT) config verify

##@ Build

.PHONY: build
build: manifests generate fmt vet ## Build manager binary.
	go build -o bin/manager cmd/main.go

.PHONY: run
run: manifests generate fmt vet ## Run a controller from your host.
	go run ./cmd/main.go

# If you wish to build the manager image targeting other platforms you can use the --platform flag.
# (i.e. docker build --platform linux/arm64). However, you must enable docker buildKit for it.
# More info: https://docs.docker.com/develop/develop-images/build_enhancements/
.PHONY: docker-build
docker-build: ## Build docker image with the manager.
	$(CONTAINER_TOOL) build -t ${IMG} .

.PHONY: docker-push
docker-push: ## Push docker image with the manager.
	$(CONTAINER_TOOL) push ${IMG}

# PLATFORMS defines the target platforms for the manager image be built to provide support to multiple
# architectures. (i.e. make docker-buildx IMG=myregistry/mypoperator:0.0.1). To use this option you need to:
# - be able to use docker buildx. More info: https://docs.docker.com/build/buildx/
# - have enabled BuildKit. More info: https://docs.docker.com/develop/develop-images/build_enhancements/
# - be able to push the image to your registry (i.e. if you do not set a valid value via IMG=<myregistry/image:<tag>> then the export will fail)
# To adequately provide solutions that are compatible with multiple platforms, you should consider using this option.
PLATFORMS ?= linux/arm64,linux/amd64,linux/s390x,linux/ppc64le
.PHONY: docker-buildx
docker-buildx: ## Build and push docker image for the manager for cross-platform support
	# copy existing Dockerfile and insert --platform=${BUILDPLATFORM} into Dockerfile.cross, and preserve the original Dockerfile
	sed -e '1 s/\(^FROM\)/FROM --platform=\$$\{BUILDPLATFORM\}/; t' -e ' 1,// s//FROM --platform=\$$\{BUILDPLATFORM\}/' Dockerfile > Dockerfile.cross
	- $(CONTAINER_TOOL) buildx create --name project-builder
	$(CONTAINER_TOOL) buildx use project-builder
	- $(CONTAINER_TOOL) buildx build --push --platform=$(PLATFORMS) --tag ${IMG} -f Dockerfile.cross .
	- $(CONTAINER_TOOL) buildx rm project-builder
	rm Dockerfile.cross

.PHONY: build-installer
build-installer: manifests generate kustomize ## Generate a consolidated YAML with CRDs and deployment.
	mkdir -p dist
	cd config/manager && $(KUSTOMIZE) edit set image controller=${IMG}
	$(KUSTOMIZE) build config/default > dist/install.yaml

##@ Deployment

ifndef ignore-not-found
  ignore-not-found = false
endif

.PHONY: install
install: manifests kustomize ## Install CRDs into the K8s cluster specified in ~/.kube/config.
	$(KUSTOMIZE) build config/crd | $(KUBECTL) apply -f -

.PHONY: uninstall
uninstall: manifests kustomize ## Uninstall CRDs from the K8s cluster specified in ~/.kube/config. Call with ignore-not-found=true to ignore resource not found errors during deletion.
	$(KUSTOMIZE) build config/crd | $(KUBECTL) delete --ignore-not-found=$(ignore-not-found) -f -

.PHONY: deploy
deploy: manifests kustomize ## Deploy controller to the K8s cluster specified in ~/.kube/config.
	cd config/manager && $(KUSTOMIZE) edit set image controller=${IMG}
	$(KUSTOMIZE) build config/default | $(KUBECTL) apply -f -

.PHONY: undeploy
undeploy: kustomize ## Undeploy controller from the K8s cluster specified in ~/.kube/config. Call with ignore-not-found=true to ignore resource not found errors during deletion.
	$(KUSTOMIZE) build config/default | $(KUBECTL) delete --ignore-not-found=$(ignore-not-found) -f -

##@ Dependencies

## Location to install dependencies to
LOCALBIN ?= $(shell pwd)/bin
$(LOCALBIN):
	mkdir -p $(LOCALBIN)

## Tool Binaries
KUBECTL ?= kubectl
KIND ?= kind
KUSTOMIZE ?= $(LOCALBIN)/kustomize
CONTROLLER_GEN ?= $(LOCALBIN)/controller-gen
ENVTEST ?= $(LOCALBIN)/setup-envtest
GOLANGCI_LINT = $(LOCALBIN)/golangci-lint

## Tool Versions
KUSTOMIZE_VERSION ?= v5.6.0
CONTROLLER_TOOLS_VERSION ?= v0.17.3
#ENVTEST_VERSION is the version of controller-runtime release branch to fetch the envtest setup script (i.e. release-0.20)
ENVTEST_VERSION ?= $(shell go list -m -f "{{ .Version }}" sigs.k8s.io/controller-runtime | awk -F'[v.]' '{printf "release-%d.%d", $$2, $$3}')
#ENVTEST_K8S_VERSION is the version of Kubernetes to use for setting up ENVTEST binaries (i.e. 1.31)
ENVTEST_K8S_VERSION ?= $(shell go list -m -f "{{ .Version }}" k8s.io/api | awk -F'[v.]' '{printf "1.%d", $$3}')
GOLANGCI_LINT_VERSION ?= v2.0.2

.PHONY: kustomize
kustomize: $(KUSTOMIZE) ## Download kustomize locally if necessary.
$(KUSTOMIZE): $(LOCALBIN)
	$(call go-install-tool,$(KUSTOMIZE),sigs.k8s.io/kustomize/kustomize/v5,$(KUSTOMIZE_VERSION))

.PHONY: controller-gen
controller-gen: $(CONTROLLER_GEN) ## Download controller-gen locally if necessary.
$(CONTROLLER_GEN): $(LOCALBIN)
	$(call go-install-tool,$(CONTROLLER_GEN),sigs.k8s.io/controller-tools/cmd/controller-gen,$(CONTROLLER_TOOLS_VERSION))

.PHONY: setup-envtest
setup-envtest: envtest ## Download the binaries required for ENVTEST in the local bin directory.
	@echo "Setting up envtest binaries for Kubernetes version $(ENVTEST_K8S_VERSION)..."
	@$(ENVTEST) use $(ENVTEST_K8S_VERSION) --bin-dir $(LOCALBIN) -p path || { \
		echo "Error: Failed to set up envtest binaries for version $(ENVTEST_K8S_VERSION)."; \
		exit 1; \
	}

.PHONY: envtest
envtest: $(ENVTEST) ## Download setup-envtest locally if necessary.
$(ENVTEST): $(LOCALBIN)
	$(call go-install-tool,$(ENVTEST),sigs.k8s.io/controller-runtime/tools/setup-envtest,$(ENVTEST_VERSION))

.PHONY: golangci-lint
golangci-lint: $(GOLANGCI_LINT) ## Download golangci-lint locally if necessary.
$(GOLANGCI_LINT): $(LOCALBIN)
	$(call go-install-tool,$(GOLANGCI_LINT),github.com/golangci/golangci-lint/v2/cmd/golangci-lint,$(GOLANGCI_LINT_VERSION))

# go-install-tool will 'go install' any package with custom target and name of binary, if it doesn't exist
# $1 - target path with name of binary
# $2 - package url which can be installed
# $3 - specific version of package
define go-install-tool
@[ -f "$(1)-$(3)" ] || { \
set -e; \
package=$(2)@$(3) ;\
echo "Downloading $${package}" ;\
rm -f $(1) || true ;\
GOBIN=$(LOCALBIN) go install $${package} ;\
mv $(1) $(1)-$(3) ;\
} ;\
ln -sf $(1)-$(3) $(1)
endef

PROJECT: Kubebuilder metadata for scaffolding new components

# Code generated by tool. DO NOT EDIT.
# This file is used to track the info used to scaffold your project
# and allow the plugins properly work.
# More info: https://book.kubebuilder.io/reference/project-config.html
cliVersion: (devel)
domain: tutorial.kubebuilder.io
layout:
- go.kubebuilder.io/v4
plugins:
  helm.kubebuilder.io/v1-alpha: {}
projectName: project
repo: tutorial.kubebuilder.io/project
resources:
- api:
    crdVersion: v1
    namespaced: true
  controller: true
  domain: tutorial.kubebuilder.io
  group: batch
  kind: CronJob
  path: tutorial.kubebuilder.io/project/api/v1
  version: v1
  webhooks:
    defaulting: true
    validation: true
    webhookVersion: v1
version: "3"

We also get launch configurations under the config/ directory. Right now, it just contains Kustomize YAML definitions required to launch our controller on a cluster, but once we get started writing our controller, it’ll also hold our CustomResourceDefinitions, RBAC configuration, and WebhookConfigurations.

config/default contains a Kustomize base for launching the controller in a standard configuration.

Each other directory contains a different piece of configuration, refactored out into its own base:

config/manager: launch your controllers as pods in the cluster
config/rbac: permissions required to run your controllers under their own service account

The Entrypoint

Last, but certainly not least, Kubebuilder scaffolds out the basic entrypoint of our project: main.go. Let’s take a look at that next…

What’s in a basic project?

Build Infrastructure

Launch Configuration

The Entrypoint