How to deploy DaemonSets Service in Kubernetes (K8s)?
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DaemonSets in Kubernetes Cluster
Like other controllers, DaemonSets manage groups of replicated Pods.
However, DaemonSet ensures that all or selected Worker Nodes run a copy of a Pod (one-Pod-per-node).
As you add nodes, DaemonSets automatically add Pods to the new nodes. As the nodes are removed from the cluster, those Pods are garbage collected.
Here is the manifest of DaemonSet:
apiVersion: apps/v1
kind: DaemonSet
metadata:
name: fluentd
namespace: kube-system
labels:
k8s-app: fluentd
spec:
selector:
matchLabels:
name: fluentd
template:
metadata:
labels:
name: fluentd
spec:
containers:
- name: fluentd
image: fluentd:latest
Create a daemonset:
kubectl create -f daemonset.yamldaemonset.apps "fluentd" created
Check the pod running:
kubectl get pods -n kube-systemNAME READY STATUS RESTARTS AGE
fluentd-7svlj 1/1 Running 0 58s
fluentd-kwm4x 1/1 Running 0 58s
fluentd-q64wf 1/1 Running 0 58s
Check no. of nodes:
kubectl get nodes
NAME STATUS ROLES AGE VERSION
gke-cluster-1-default-pool-a6a57f2a-77wb Ready < none > 6h v1.11.6-gke.2
gke-cluster-1-default-pool-a6a57f2a-xkgz Ready < none > 6h v1.11.6-gke.2
gke-cluster-1-default-pool-a6a57f2a-z2bx Ready < none > 6h v1.11.6-gke.2
Display your daemon sets:
kubectl get daemonsets
NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE AGE
fluentd 3 3 3 3 3 5m
Get details of a daemonset:
kubectl describe daemonset fluentd
Edit a daemonset:
kubectl edit daemonset fluentd
Delete a daemonset:
kubectl delete daemonset fluentd
daemonset.apps โfluentdโ deleted
Some uses of a DaemonSet are:
running a cluster storage daemon, such as glusterd, ceph, on each node.
running a logs collection daemon on every node, such as fluentd or logstash.
running a node monitoring daemon on every node, such as Prometheus Node Exporter, AppDynamics Agent, Datadog agent, New Relic agent, etc.
Running Pods on Only Some Nodes
If you specify a .spec.template.spec.mode selector, then the DaemonSet controller will create Pods on nodes which match that node selector.
spec:
nodeSelector:
environment: prod
Now, If you mention a .spec.template.spec.affinity, then DaemonSet controller will be creating the Pods on nodes which will be matching the node affinity.
spec:
tolerations:
- key: node-role.kubernetes.io/master
effect: NoSchedule
In case you will not specify anything, then the controller will be creating Pods on every node of the cluster.
For Reference
