CodeBlanks Logo Icon CodeBlanks
Login Register

Summary - DaemonSet

Combine YAML and nodeSelector to write a DaemonSet.

Summary: DaemonSet

In this group:

  • A DaemonSet runs exactly one pod on each eligible node; when a node is added/removed, the pod is added/removed too.
  • YAML: apps/v1, kind: DaemonSet, selector + template; there is no replicas.
  • nodeSelector/nodeAffinity select nodes; tolerations allow tainted nodes.
  • Uses: log collection, monitoring, networking, storage and security agents; resource limits multiply with the node count.
  • Updates: RollingUpdate (maxUnavailable) or OnDelete; the rollout commands work.
kubectl get ds -A
kubectl rollout status ds/node-exporter -n izleme

Practice A collector on every node

Write a DaemonSet template's spec section (starting with spec:): under tolerations, key: node-role.kubernetes.io/control-plane, operator: Exists, effect: NoSchedule; container named fluent-bit, image fluent/fluent-bit:3.1.

Starter code

terminal
# buraya yaz

Sample solution

terminal
spec:
  tolerations:
    - key: node-role.kubernetes.io/control-plane
      operator: Exists
      effect: NoSchedule
  containers:
    - name: fluent-bit
      image: fluent/fluent-bit:3.1

Expected output

daemonset.apps/fluent-bit configured
NAME         DESIRED   CURRENT   READY
fluent-bit   3         3         3

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 If a log-collector DaemonSet doesn't run on the control-plane node, what is the likely cause?

  • The image is wrong
  • The namespace is wrong
  • There's no toleration for the NoSchedule taint on the node Correct answer
  • replicas is missing

Explanation: Control-plane nodes are tainted by default.

2 Allow the taint.

Question 
      ____:
        - key: node-role.kubernetes.io/control-plane
          operator: Exists
          effect: NoSchedule
Answer 
      tolerations:
        - key: node-role.kubernetes.io/control-plane
          operator: Exists
          effect: NoSchedule

Explanation: tolerations let a pod be placed on a tainted node.

3 Match.

Term Meaning
DaemonSet Per node
nodeSelector Node selection
tolerations Taint allowance
OnDelete Controlled update

All lessons in Advanced

1 Ingress

  1. What is Ingress?
  2. Ingress controller
  3. Ingress YAML
  4. Host and path
  5. TLS termination
  6. Summary - Ingress

2 Helm

  1. What is Helm?
  2. Chart structure
  3. helm install
  4. values.yaml
  5. helm upgrade
  6. Summary - Helm

3 StatefulSet

  1. What is a StatefulSet?
  2. StatefulSet YAML
  3. Stable identity
  4. VolumeClaimTemplate
  5. Ordered startup
  6. Summary - StatefulSet

4 DaemonSet

  1. What is a DaemonSet?
  2. DaemonSet YAML
  3. Node selector
  4. DaemonSet use cases
  5. Updating a DaemonSet
  6. Summary - DaemonSet

5 Job and CronJob

  1. What is a Job?
  2. Job YAML
  3. completions and parallelism
  4. What is a CronJob?
  5. CronJob YAML
  6. Summary - Job and CronJob

6 PV and PVC

  1. What is a PersistentVolume?
  2. PersistentVolumeClaim
  3. StorageClass
  4. Access modes
  5. Mounting a PVC to a Pod
  6. Summary - PV and PVC

7 HPA - Autoscaling

  1. What is an HPA?
  2. HPA YAML
  3. CPU threshold
  4. Min and max replicas
  5. Metrics server
  6. Summary - HPA

8 RBAC

  1. What is RBAC?
  2. Role and ClusterRole
  3. RoleBinding
  4. ServiceAccount
  5. Verbs and resources
  6. Summary - RBAC

9 Prometheus and Grafana

  1. What is Prometheus?
  2. ServiceMonitor
  3. What is Grafana?
  4. PromQL basics
  5. Alertmanager
  6. Summary - Monitoring

10 EFK logging

  1. Centralized logging
  2. Fluentd
  3. Elasticsearch
  4. Kibana
  5. DaemonSet logging
  6. Summary - Logging

11 Project: Production app

  1. Production design
  2. Database with StatefulSet
  3. Ingress and TLS
  4. Scaling with HPA
  5. Putting it together - production

12 Advanced final

  1. Challenge - Ingress
  2. Challenge - StatefulSet
  3. Challenge - CronJob
  4. Challenge - RBAC
  5. Challenge - Advanced project