This article describes How to Create & Update & Scale & Delete Deployment with kubectl in Kubernetes.

Kubernetes is a portable, extensible, open-source platform for managing containerized workloads and services, that facilitates both declarative configuration and automation. It has a large, rapidly growing ecosystem. Kubernetes services, support, and tools are widely available.

The name Kubernetes originates from Greek, meaning helmsman or pilot. Google open-sourced the Kubernetes project in 2014.

Creating and exploring a nginx deployment
You can run an application by creating a Kubernetes Deployment object, and you can describe a Deployment in a YAML file.
For example, this YAML file describes a Deployment that runs the nginx:1.7.9 Docker image:

cat << EOF > nginx-deployment.yaml
apiVersion: apps/v1 # for versions before 1.9.0 use apps/v1beta2
kind: Deployment
metadata:
name: nginx-deployment
spec:
selector:
matchLabels:
app: nginx
replicas: 2 # tells deployment to run 2 pods matching the template
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx:1.7.9
ports:
- containerPort: 80
EOF

ls *nginx* -al

Create a Deployment based on the YAML file:
kubectl apply -f nginx-deployment.yaml

Display information about the Deployment:
kubectl describe deployment nginx-deployment

List the pods created by the deployment:
kubectl get pods -l app=nginx -o wide
watch kubectl get pods -l app=nginx -o wide

Display information about a pod:
kubectl describe pod <pod-name>
kubectl describe pod nginx-deployment-54f57cf6bf-kptzh
kubectl describe pod nginx-deployment-54f57cf6bf-kptzh nginx-deployment-54f57cf6bf-qxdpr

Updating the deployment
You can update the deployment by applying a new YAML file. This YAML file specifies that the deployment should be updated to use nginx 1.8.
cat << EOF > nginx-deployment-update.yaml
apiVersion: apps/v1 # for versions before 1.9.0 use apps/v1beta2
kind: Deployment
metadata:
name: nginx-deployment
spec:
selector:
matchLabels:
app: nginx
replicas: 2
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx:1.8 # Update the version of nginx from 1.7.9 to 1.8
ports:
- containerPort: 80
EOF

ls *nginx* -al

Apply the new YAML file:
kubectl apply -f nginx-deployment-update.yaml

Watch the deployment create pods with new names and delete the old pods:
watch -d kubectl get pods -l app=nginx -o wide
watch -b -c -d kubectl get pods -o wide -l app=nginx

Scaling the application by increasing the replica count
You can increase the number of pods in your Deployment by applying a new YAML file. This YAML file sets replicas to 4, which specifies that the Deployment should have four pods:
cat << EOF > nginx-deployment-scale.yaml
apiVersion: apps/v1 # for versions before 1.9.0 use apps/v1beta2
kind: Deployment
metadata:
name: nginx-deployment
spec:
selector:
matchLabels:
app: nginx
replicas: 5 # Update the replicas from 2 to 5
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx:1.8
ports:
- containerPort: 80
EOF

Apply the new YAML file:
kubectl apply -f nginx-deployment-scale.yaml

Verify that the Deployment has four pods:
kubectl get pods -l app=nginx -o wide
watch kubectl get pods -l app=nginx -o wide

Deleting a deployment
Delete the deployment by name:
kubectl delete deployment nginx-deployment

Now you can find some examples in this video.

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