Helm and Kustomize

Helm and Kustomize · Kubernetes · aiiolar

Syntax	Gives
`{{ .Values.image.tag }}`	a value
`{{ .Release.Name }}`	release name
`{{ .Chart.Name }}`	chart name
`{{ if .Values.ingress.enabled }}`	conditional
`{{ range .Values.env }}`	loop

Pipeline: {{ .Values.name | default "app" | quote }}

3. Example and Mistakes

helm template renders locally, never touches the cluster

bash

helm create myapp
helm template myapp ./myapp -f prod.yaml
helm lint ./myapp

scaffold, render, check

Common mistakes

Pasted YAML breaks indentation: use {{ toYaml .Values.resources | nindent 12 }}. Avoid --set on lists or nested keys: use a values file and quote strings that look like numbers or booleans.

1. Releases and State

Release = one named install of a chart in a namespace
Same chart, many releases under different names
State = Secret sh.helm.release.v1.<name>.v<rev>
No Tiller; each upgrade makes a new revision

2. Lifecycle Commands

bash

helm install web ./myapp -n prod --create-namespace -f prod.yaml
helm upgrade --install web ./myapp -f prod.yaml
helm upgrade web ./myapp --set image.tag=1.4
helm history web
helm rollback web 2

upgrade --install is the idempotent form
rollback web 2 = new revision with revision 2's config

Command	Shows
`helm list -A`	all releases
`helm status web`	state
`helm get values web`	overrides; `--all` adds defaults
`helm get manifest web`	rendered YAML
`helm uninstall web`	removes release

3. Safe Deploys

--atomic: auto rollback on failure, implies --wait
--wait: block until resources are ready
--timeout: sets the limit
helm diff upgrade (plugin) previews changes

Upgrade resets overrides

Without --reuse-values or the original -f, overrides revert to chart defaults. Pass the same values files every time.

1. Base and overlay

Template-free plain YAML, built into kubectl
Directory with kustomization.yaml = one unit
Base = common manifests
Overlay lists base under resources:, adds env changes, base untouched

text

base/
  deployment.yaml
  service.yaml
  kustomization.yaml
overlays/
  dev/kustomization.yaml
  prod/kustomization.yaml

layout

yaml

resources:
  - ../../base
namePrefix: prod-
namespace: prod
replicas:
  - name: web
    count: 5

overlays/prod/kustomization.yaml

2. Transformers and patches

Key	Effect
`namePrefix`, `namePrefix`	rename resources
`namespace`	set namespace
`commonLabels`	add labels
`images`	change name or tag
`replicas`	set count
`configMapGenerator`, `secretGenerator`	add hash suffix

Hash: new content, new name, references rewritten, pods roll
patches: with path or inline target
Strategic merge: by structure, containers by name
JSON 6902: op/path/value

3. Commands and mistakes

Preview: kubectl kustomize overlays/prod
Apply: kubectl apply -k overlays/prod
Delete: kubectl delete -k overlays/prod

Mistakes

A patch matching no name or kind fails the build. commonLabels rewrites immutable selectors.

1. Two Tools, Two Jobs

	Helm	Kustomize
Method	Go templates + values	base + overlays + patches
Output	rendered from templates	always valid YAML
State	release history in cluster	none stored in cluster
Rollback	`helm rollback`, hooks	none built in
Ecosystem	chart repositories	built into kubectl
Best for	third-party, parameterized apps	your manifests, per-env differences

2. Typical Choice

3. Combining Them

Render with Helm, then patch the output with Kustomize
helmCharts: in kustomization.yaml inflates a chart
Argo CD and Flux support both

bash

helm template web ./myapp | kubectl apply -f -
kustomize build --enable-helm overlays/prod

helmCharts needs --enable-helm

One owner per resource

kubectl apply -k on resources a Helm release owns causes drift and conflicting field managers.

1. Helm Commands

bash

helm create myapp; helm lint ./myapp
helm template web ./myapp -f prod.yaml
helm upgrade --install web ./myapp -n prod
helm list -A; helm status web
helm history web; helm rollback web 2
helm uninstall web

upgrade --install is the idempotent deploy

2. Values and Safety Flags

Precedence: chart values.yaml < -f files (in order) < --set
helm get values web shows what is applied

Flag	Effect
`--atomic`	rolls back on failure, implies `--wait`
`--wait` / `--timeout`	block until ready / set the limit
`-n ns` / `--create-namespace`	target namespace / create it
`--dry-run --debug`	render only, no install

3. Kustomize

yaml

resources: [../../base]
namePrefix: prod-
namespace: prod
images: [{name: web, newTag: "1.4"}]
replicas: [{name: web, count: 3}]
configMapGenerator: [{name: cfg, literals: [A=1]}]
patches: [{path: patch.yaml}]

kustomization.yaml in an overlay

Command	Does
`kubectl kustomize <dir>`	preview output
`kubectl apply -k <dir>`	apply
`kubectl delete -k <dir>`	delete

4. Which Tool

Rule of thumb

Helm for packaged or third-party apps. Kustomize for plain in-house YAML per environment.

Helm Charts, Values and Templates

1. What a Chart Is

2. Values and Templates

Helm Install, Upgrade, Rollback and Releases

Kustomize Bases, Overlays and Patches

Choosing Between Helm and Kustomize