Difference between a Deployment and a DaemonSet in Kubernetes

Question

What is the difference between a Deployment and a DaemonSet in Kubernetes?

Answer 1

Hey @Ali, 

A deployment provides declarative updates for replicasets and pods. What are declarative updates? So basically, you describe the desired state in your deployment object and the deployment controller will change the actual state to the desired state in a very controlled fashion. 

Use-cases:

• Create a replicationController
• Declare a new state of the pod
• Rollback feature can be used
• scaling for efficient deployment can be used
• Clean-up older replicaSets

Answer 2

Adding to @Rohit's answer, I'll explain about the daemonSet. DaemonSet ensures that all nodes are running a copy of the pods. If new nodes are added to the cluster, pods get equally distributed amongst the newly added nodes. This is taken care of by the DaemonSet. 

DeamonSet yaml look something like this:

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: daemonset
  namespace: kube-system
  labels:
    k8s-app: fluentd-logging
spec:
  selector:
    matchLabels:
      name: daemonset
  template:
    metadata:
      labels:
        name: daemonset
    spec:
      tolerations:
      - key: node-role.kubernetes.io/master
        effect: NoSchedule
      containers:
      - name: daemonset
        image: k8s.gcr.io/fluentd-elasticsearch:1.20
        resources:
          limits:
            memory: 200Mi
          requests:
            cpu: 100m
            memory: 200Mi
        volumeMounts:
        - name: varlog
          mountPath: /var/log
        - name: varlibdockercontainers
          mountPath: /var/lib/docker/containers
          readOnly: true
      terminationGracePeriodSeconds: 30
      volumes:
      - name: varlog
        hostPath:
          path: /var/log
      - name: varlibdockercontainers
        hostPath:
          path: /var/lib/docker/containers