Troubleshooting OpenShift Container Platform 4.x: DNS

Solution Verified - Updated -

Environment

  • Red Hat OpenShift Container Platform 4.x

Issue

  • How to troubleshoot DNS issues in RHCOS 4.x?

Diagnostic Steps

1. Check the cluster operator to see if it is available:

# oc get clusteroperator dns

2. Check to see if there are pods and services created under openshift-dns-operator

# oc get all  -n openshift-dns-operator

3. Check the logs of dns-operator pod

# oc logs pod/`oc get pods -o=jsonpath="{.items[0].metadata.name}" -n openshift-dns-operator` -n openshift-dns-operator

4. Check dns components are running under openshift-dns project:

# oc get all  -n openshift-dns

5. Check the pod resolver is pointing to DNS Service IP:

# export PODS=`oc get pods -o=jsonpath="{.items[*].metadata.name}" -n openshift-apiserver`
# for pod in $PODS;do oc exec $pod -n openshift-apiserver -- cat /etc/resolv.conf ;done;

6. You can check coredns container logs on node:

# export PODS=`oc get pods -o=jsonpath="{.items[*].metadata.name}" -n openshift-dns`
# for pod in $PODS;do oc logs $pod -c dns -n openshift-dns &> $pod.log;done;

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