Kubernetes resource management with YAML manifests¶

In Kubernetes, the desired state of the cluster—such as which applications are running, on which nodes, and with what resources—is defined using YAML manifests^[400-devops-06-kubernetes-k8s-paas-05k8scicd.md]. These declarative configuration files serve as the source of truth for the cluster, allowing administrators to manage complex deployments and infrastructure configurations efficiently^[400-devops-06-kubernetes-k8s-paas-05k8scicd.md].

Deployment and Configuration¶

The typical workflow involves creating a directory to store YAML files and defining resources such as Deployments, Services, and Ingress^[400-devops-06-kubernetes-k8s-paas-05k8scicd.md].

Example Directory Structure¶

A common practice is to organize manifests by application or component on a dedicated host (e.g., an Ops server)^[400-devops-06-kubernetes-k8s-paas-05k8scicd.md].

mkdir /data/k8s-yaml
cd /data/k8s-yaml
mkdir jenkins
cd jenkins

Deployment Manifest¶

A Deployment resource (dp.yaml) defines the container image, replicas, ports, and environment variables^[400-devops-06-kubernetes-k8s-paas-05k8scicd.md].

kind: Deployment
apiVersion: extensions/v1beta1
metadata:
  name: jenkins
  namespace: infra
  labels: 
    name: jenkins
spec:
  replicas: 1
  selector:
    matchLabels: 
      name: jenkins
  template:
    metadata:
      labels: 
        app: jenkins 
        name: jenkins
    spec:
      volumes:
      - name: data
        nfs: 
          server: hdss7-200
          path: /data/nfs-volume/jenkins_home
      containers:
      - name: jenkins
        image: harbor.od.com/infra/jenkins:v2.190.3
        imagePullPolicy: IfNotPresent
        ports:
        - containerPort: 8080
          protocol: TCP
        volumeMounts:
        - name: data
          mountPath: /var/jenkins_home
      imagePullSecrets:
      - name: harbor

Service Manifest¶

A Service resource (svc.yaml) creates a stable network endpoint to access the running pods^[400-devops-06-kubernetes-k8s-paas-05k8scicd.md].

kind: Service
apiVersion: v1
metadata: 
  name: jenkins
  namespace: infra
spec:
  ports:
  - protocol: TCP
    port: 80
    targetPort: 8080
  selector:
    app: jenkins

Ingress Manifest¶

An Ingress resource (ingress.yaml) manages external access to the services, typically via HTTP/HTTPS^[400-devops-06-kubernetes-k8s-paas-05k8scicd.md].

kind: [Ingress](<./ingress.md>)
apiVersion: extensions/v1beta1
metadata: 
  name: jenkins
  namespace: infra
spec:
  rules:
  - host: jenkins.od.com
    http:
      paths:
      - path: /
        backend: 
          serviceName: jenkins
          servicePort: 80

Applying Manifests¶

Once the YAML files are prepared, they are applied to the cluster using the kubectl apply command^[400-devops-06-kubernetes-k8s-paas-05k8scicd.md]. These files are often hosted on an internal HTTP server for easy access and version control^[400-devops-06-kubernetes-k8s-paas-05k8scicd.md].

[kubectl](<./kubectl.md>) apply -f http://k8s-yaml.od.com/jenkins/dp.yaml
[kubectl](<./kubectl.md>) apply -f http://k8s-yaml.od.com/jenkins/svc.yaml
[kubectl](<./kubectl.md>) apply -f http://k8s-yaml.od.com/jenkins/ingress.yaml

Private Registry Authentication¶

When deploying container images from a private registry (like Harbor), a secret must be created within the specific namespace to store the authentication credentials^[400-devops-06-kubernetes-k8s-paas-05k8scicd.md].

[kubectl](<./kubectl.md>) create secret docker-registry harbor \
  --docker-server=harbor.od.com \
  --docker-username=admin \
  --docker-password=Harbor12345 \
  -n infra

This secret is then referenced in the Deployment manifest under spec.template.spec.imagePullSecrets^[400-devops-06-kubernetes-k8s-paas-05k8scicd.md].

Configuration Management¶

YAML manifests can be used to inject environment variables and mount storage volumes.

Environment Variables: Used to pass configuration at runtime, such as Java options or application arguments^[400-devops-06-kubernetes-k8s-paas-05k8scicd.md].
Volumes: Manifests support various volume types, including nfs for persistent storage and hostPath for accessing host machine files^[400-devops-06-kubernetes-k8s-paas-05k8scicd.md].

Kubernetes
[[Docker]]
CI/CD
Ingress

Sources¶

400-devops-06-kubernetes-k8s-paas-05k8scicd.md