Kubernetes- DaemonSet

 A DaemonSet ensures that all (or some) Nodes run a copy of a Pod. As nodes are added to the cluster, Pods are added to them. As nodes are removed from the cluster, those Pods are garbage collected. Deleting a DaemonSet will clean up the Pods it created.

Some typical uses of a DaemonSet are:

• running a cluster storage daemon on every node
• running a logs collection daemon on every node
• running a node monitoring daemon on every node

In a simple case, one DaemonSet, covering all nodes, would be used for each type of daemon. A more complex setup might use multiple DaemonSets for a single type of daemon, but with different flags and/or different memory and cpu requests for different hardware types.

1. Deploy Pod on "all" worker nodes inside k8s cluster using DaemonSet

1a. YAML File:

# nginx-ds-allnodes.yaml

apiVersion: apps/v1

kind: DaemonSet

metadata:

  name: nginx-ds

spec:

  template:

    metadata:

      labels:

        name: nginx

    spec:

      containers:

      - name: nginx

        image: nginx

  selector:

    matchLabels:

      name: nginx

1b. Create | Display | Validate

kubectl create -f nginx-ds-allnodes.yaml

kubectl get po -o wide

kubectl get ds

kubectl describe ds nginx-ds

kubectl delete ds nginx-ds

 Deploy Pod on "Subset" of worker nodes inside k8s cluster using DaemonSet

 Attach label to the nodes

kubectl get nodes

kubectl label nodes worker1 worker2 disktype=ssd

kubectl get nodes --show-labels

YAML

# nginx-ds-subsetnodes.yaml

apiVersion: apps/v1

kind: DaemonSet

metadata:

  name: nginx-ds

spec:

  template:

    metadata:

      labels:

        name: nginx

    spec:

      containers:

      - name: nginx-container

        image: nginx

      nodeSelector:

        disktype: ssd

  selector:

    matchLabels:

      name: nginx

Create | Display | Validate

kubectl create -f nginx-ds-subsetnodes.yaml

kubectl get po -o wide

kubectl get ds

kubectl describe ds nginx-ds

 Cleanup

kubectl delete ds nginx-ds

kubectl get po

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