Skip to content
CKATroubleshootingTwo nodesEasy

Cluster DNS down

Scenario cka-trb-005 · about 5 minutes · 5 points · 3 grader checks

Service name resolution has stopped working; investigate and restore the cluster DNS component.

  • troubleshooting
  • coredns
  • dns
  • kube-system

What you will practise

  • Locate the cluster DNS Deployment
  • Diagnose a Deployment with zero replicas
  • Restore a system component without deleting it

Start this lab

With the CLI installed and signed in, this command provisions a two nodes cluster on your Mac, applies the scenario setup and prints the task below.

goldenkube start cka-trb-005

Task

The task text exactly as the CLI shows it. Solve it on the cluster, then run goldenkube submit.

Cluster DNS is not working: nothing in the cluster can resolve service names. Investigate the cluster DNS component in namespace "kube-system" and restore it. When you are done, the "coredns" Deployment must have at least 1 ready replica. Do not delete the Deployment.

Requirements and details

Certification
CKA · Certified Kubernetes Administrator
Domain
Troubleshooting
Difficulty
Easy
Cluster topology
Two nodes
Cluster features
None beyond the base cluster
Recommended time
5 minutes
Points
5
Grader checks
3
Kubernetes version
1.37
Minimum CLI version
0.1.0
Scenario version
1
Published

Grading runs locally: 3 state checks read your cluster when you submit; the scenario passes when every check passes. Hints, the reference solution and the check definitions are available only inside the CLI, not on this page.

Install the CLICreate a free account

More Troubleshooting labs

CKATroubleshootingMedium

Worker NotReady: kubelet stopped

A worker node reports NotReady; diagnose and restore it without recreating the node.

Two nodes · ~7 min · 7 points

  • troubleshooting
  • node
  • kubelet
  • notready

goldenkube start cka-trb-001

CKATroubleshootingMedium

Worker NotReady: kubelet fails to start

The kubelet on a worker refuses to start; find the misconfiguration and fix it on the node.

Two nodes · ~8 min · 7 points

  • troubleshooting
  • node
  • kubelet
  • systemd
  • configuration

goldenkube start cka-trb-002

CKATroubleshootingHard

kube-apiserver static pod broken

kubectl cannot reach the cluster; repair the API server from the control plane node.

Single node · ~8 min · 8 points

  • troubleshooting
  • kube-apiserver
  • static-pod
  • control-plane
  • crictl

goldenkube start cka-trb-003

CKATroubleshootingMedium

Worker NotReady: container runtime down

A worker is NotReady although its kubelet runs; find the underlying runtime problem and fix it.

Two nodes · ~6 min · 6 points

  • troubleshooting
  • node
  • containerd
  • cri
  • kubelet

goldenkube start cka-trb-004

Independent community project, not affiliated with or endorsed by CNCF or The Linux Foundation. Lab results are practice feedback, not an exam score.