iti-k8s.md

Volumes

emptyDir

• Used as temporary storage

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      volumes:
        - name: data 
          emptyDir: {}

      containers:
      - image: nginx
        name: nginx
        volumeMounts:
        - name: data 
          mountPath: /data

hostPath

• Relies on storing data on the kubernetes node
• Data isn't replicated, it's only available on that single node

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      volumes:
        - name: kube-data  
          hostPath:
            path: /tmp/kubernetes

      containers:
      - image: nginx
        name: nginx
        volumeMounts:
        - name: kube-data 
          mountPath: /kube-data

---

NFS Server Setup

1. NFS Server - Virtual Machine (EC2) => nfs-server
2. Worker Node - nfs-client

sudo apt install nfs-kernel-server -y

# Create main directory
sudo mkdir -pv /mnt/nfs

# Set directory permissions
sudo chown -R nobody:nogroup /mnt/nfs
sudo chmod 777 /mnt/nfs

# Modify exports file to allow any client to access the server mount 
echo '/mnt/nfs *(rw,no_root_squash,no_subtree_check)' | sudo tee -a /etc/exports

# Export NFS shared directory
sudo exportfs -a

# Restart nfs server
sudo systemctl restart nfs-kernel-server

NFS Client Setup

sudo apt install nfs-common -y

---

Create PV Via NFS

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-nfs
spec:
  capacity:
    storage: 1Gi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteOnce
  persistentVolumeReclaimPolicy: Recycle
  storageClassName: nfs 
  mountOptions:
    - hard
    - nfsvers=4.1
  nfs:
    path: /mnt/nfs/nginx
    server: 192.168.100.12

Create PVC to bind to the PV

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc-nfs
  namespace: nginx
spec:
  accessModes:
  - ReadWriteOnce
  storageClassName: nfs
  volumeName: pv-nfs
  resources:
    requests:
      storage: 1Gi

Create Nginx Deployment with PVC used as mount

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      volumes:
      - name: nginx-volume
        persistentVolumeClaim:
          claimName: pvc-nfs
      containers:
      - image: nginx
        name: nginx
        ports:
        - containerPort: 80
        volumeMounts:
        - name: nginx-volume
          mountPath: /usr/share/nginx/html

---

Dynamic Provisioning

• PVCs result in a PVC being created

---

Probes

Startup Probes

Readiness Probes

Liveness Probes