📄 YAML

Almost everything in Kubernetes is described in YAML files: you write what you want ("2 pods with this image") and the cluster makes it happen. This page shows how to read, generate, validate and apply these files.

info

YAML files are applied with kubectl. The Nuvion Panel does not have a YAML editor for cluster resources.

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🚀 Before you start

• Have cluster access configured (see Cluster Access).

📖 The structure of every Kubernetes YAML

apiVersion: apps/v1
kind: Deployment
metadata:
  name: exemplo
spec:
  replicas: 1

Field	What it is
apiVersion	The resource's API version
kind	The type (Pod, Deployment, Service...)
metadata	Name, labels (labels) and namespace
spec	What you want to exist

📏 YAML rules

• Use 2 spaces to indent. Never use Tab.
• Lists start with - (dash and space).
• Text with : or special characters goes in quotes.
• Several resources in the same file are separated by ---.

🚀 1. See the YAML of an existing resource

kubectl get deployment NAME -o yaml

The output has extra fields, filled in by the cluster (such as status). It is for reference.

🚀 2. Generate a ready-made template

Instead of writing from scratch, let kubectl generate it and save it to a file:

kubectl create deployment meu-app --image=nginx:1.27 --replicas=2 --dry-run=client -o yaml > meu-app.yaml

--dry-run=client creates nothing in the cluster, it only generates the text.

🚀 3. Look up a field's documentation

kubectl explain deployment.spec.replicas
kubectl explain deployment.spec.strategy

This command explains each field, without leaving the terminal.

🚀 4. Validate before applying

kubectl apply -f meu-app.yaml --dry-run=server
kubectl diff -f meu-app.yaml

The first asks the cluster to validate the file without creating anything. The second shows what will change compared to what already exists.

🚀 5. Apply

kubectl apply -f meu-app.yaml

apply creates the resource if it does not exist and updates it if it does. Use the same command to create and to change.

🚀 6. Change an existing resource

There are two ways:

Way	Command	When to use
Edit the file	Change meu-app.yaml and run kubectl apply -f meu-app.yaml	Recommended: the file remains the source of truth
Edit directly in the cluster	kubectl edit deployment meu-app	Quick adjustments and testing

🚀 7. Delete using the file

kubectl delete -f meu-app.yaml

✅ How to know it worked

kubectl get deployment meu-app

The Deployment appears with READY 2/2.

🔒 Best practices

• Store YAML files in a repository (Git), without passwords. For sensitive data, use Secrets.
• Run kubectl diff before applying in production.
• Use one file per application, with clear names.

❗ Common problems

Message	Cause	Solution
error converting YAML to JSON	Indentation error or Tab in the file	Review the spaces (2 per level)
unknown field "..."	Field misspelled or in the wrong place	Use kubectl explain to see the correct name
no matches for kind	Incorrect apiVersion or kind	Check with kubectl api-resources
selector does not match template labels	matchLabels differs from labels	Use the same label in both
field is immutable	Field that cannot be changed after creation	Delete and create again

🧹 Cleanup

kubectl delete -f meu-app.yaml
rm meu-app.yaml

🧠 Questions?

Talk to our SaveinCloud technical support team!