Kubernetes How to confirm DNS is working
I have successfully created a Kubernetes POD/Service using MiniKube on windows. But I would now like to ensure that DNS is working correctly.
The DNS service is shown as running
.\kubectl get pod -n kube-systemWhich shows me the kube-dns pod is running
I also have the DNS add on shown as running
So I then want to verify that DNS is working, Ideally I want to test that PODs that have a service on top of them can lookup the service by DNS name.
But I started simple like this, where I get my running POD
So now that I have my POD name, I want to try do simple DNS lookup in it using the following commmand
.\kubectl exec simple-sswebapi-pod-v1-f7f8764b9-xs822 -- nslookup google.comWhere I am using the kubectl exec to try and run this nslookup in the POD that was found (running I should point out above).
But I get this error
Why would it not be able to find nslookup inside POD. All the key things seem to be ok
- Kube-DNS pod is running (as shown above)
- DNS AddOn is installed and running (as shown above)
What am I missing, is there something else I need to enable for DNS lookups to work inside my PODs?
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2 Answers
To do it like this your container needs to include the command you want to use inside of the built image.
Sidenote: kubectl debug is coming to kube in near future https://github.com/kubernetes/kubernetes/issues/45922 which will help solve things like that by enabling you to attach a custom container to existing pod and debug in it
So more on this I installed busybox into a POD to allow me to use nslookup and this enabled me to do this
So this looks cool, but should I not be able to ping that service either by its IP address or by its DNS name which seems to be resolving just fine as shown above.
If I ping google.com inside busybox command prompt all is ok, but when I do a ping for either this IP address of this service of the DNS names, it never gets anywhere.
DNS lookup is clearly working. What am I missing?