Configuration file structure

Each configuration file has 3 parts being:

• Metadata

• Specification (spec)

  • Has component specific configuration

• Status

  • Is automatically added by Kubernetes
  • The information being placed there comes from etcd
  • To get the deployment config with the current status we run:

  kubectl get deployment -o yaml
  

Using configuration files

# Apply a configuration file
kubectl apply -f <FILENAME>

# Delete with a configuration file
kubectl delete -f <FILENAME>

Examples

nginx-deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
	name: nginx-deployment
	labels:
		app: nginx
spec:
	replicas: 1
	selector:
		matchLabels:
			app: nginx
	template:
		metadata:
			labels:
				app: nginx
		spec:
			containers:
			- name: nginx
				image: nginx:1.16
				ports:
				- containerPort: 80

<aside> 💡 If we need to change some configuration (i.e: replicas), we can just update the file and execute kubectl apply -f nginx-deployment.yaml again.

</aside>

Connecting Services to Deployments

The Service references the Deployment in the selector area, which is defined in the labels.app of the deployment.

apiVersion: apps/v1
kind: Deployment
metadata:
	name: nginx-deployment
	labels:
		app: nginx
spec:
	replicas: 1
	selector:
		matchLabels:
			app: nginx
	template:
		metadata:
			labels:
				app: nginx
		spec:
			containers:
			- name: nginx
				image: nginx:1.16
				ports:
				- containerPort: 8080

apiVersion: v1
kind: Service
metadata:
	name: nginx-service
spec:
	selector:
		app: nginx
	ports:
	- protocol: TCP
		port: 80
		targetPort: 8080

Creating a component in a namespace

By default every component is created in the default namespace, we can define it by specifying a namespace in metadata.namespace:

apiVersion: v1
kind: Service
metadata:
	name: nginx-service
	**namespace: my-namespace**
spec:
	selector:
		app: nginx
	ports:
	- protocol: TCP
		port: 80
		targetPort: 8080