I've install a Kubernetes 1.2.4 on 3 minons/master (1 master/minion, 2 minions) and installed the SkyDNS addons. After fixing SSL cert problems, I know have SkyDNS working. But kubeletes still says that I didn't set cluster-dns and cluster-domain.

(see edits at the bottom)

But you can see --cluster-dns=192.168.0.10 --cluster-domain=cluster.local:

ps ax | grep kubelet
18717 ?        Ssl    0:04 /opt/kubernetes/bin/kubelet --logtostderr=true --v=0 --address=0.0.0.0 --port=10250 --hostname-override=k8s-minion-1 --api-servers=http://k8s-master:8080 --allow-privileged=false  --cluster-dns=192.168.0.10 --cluster-domain=cluster.local 

Launching this pod:

apiVersion: v1
kind: Pod
metadata:
  name: busybox
  namespace: default
spec:
  containers:
  - image: busybox
    command:
      - sleep
      - "3600"
    imagePullPolicy: IfNotPresent
    name: busybox
  restartPolicy: Always

I see:

kubectl describe pod busybox
7m      7m      2   {kubelet k8s-master.XXX}                    Warning     MissingClusterDNS   kubelet does not have ClusterDNS IP configured and cannot create Pod using "ClusterFirst" policy. Falling back to DNSDefault policy.

I restarted kubelete services before to launch this pod, and I have no other pod running.

If I launch docker container using "--dns" option:

docker run --rm -it --dns 192.168.0.10 busybox nslookup cluster.local
Server:    192.168.0.10
Address 1: 192.168.0.10

Name:      cluster.local
Address 1: 192.168.0.10
Address 2: 172.16.50.2
Address 3: 192.168.0.1
Address 4: 172.16.96.3


docker run --rm -it --dns 192.168.0.10 busybox cat /etc/resolv.conf
search XXX YYYY 
nameserver 192.168.0.10

That's absolutly normal (I've hidden my client dns)

But the pod says something else:

kubectl exec busybox -- nslookup cluster.local
Server:    XXX.YYY.XXX.YYY
Address 1: XXX.YYYY.XXXX.YYY XXX.domain.fr

nslookup: can't resolve 'cluster.local'
error: error executing remote command: Error executing command in container: Error executing in Docker Container: 1

I tried to set "--dns" option to the docker daemon, but the error is the same.

See that logs:

kubectl get  pods --namespace=kube-system
NAME                 READY     STATUS    RESTARTS   AGE
kube-dns-v11-osikn   4/4       Running   0          13m

And:

kubectl logs kube-dns-v11-osikn kube2sky --namespace=kube-system
I0621 15:44:48.168080       1 kube2sky.go:462] Etcd server found: http://127.0.0.1:4001
I0621 15:44:49.170404       1 kube2sky.go:529] Using https://192.168.0.1:443 for kubernetes master
I0621 15:44:49.170422       1 kube2sky.go:530] Using kubernetes API <nil>
I0621 15:44:49.170823       1 kube2sky.go:598] Waiting for service: default/kubernetes
I0621 15:44:49.209691       1 kube2sky.go:660] Successfully added DNS record for Kubernetes service.

"Using kubernetes API <nil>" is a problem, isn't it ? edit: I forced kube-master-url in the pod to let kube2sky contacting the master.

kubectl logs kube-dns-v11-osikn skydns --namespace=kube-system
2016/06/21 15:44:50 skydns: falling back to default configuration, could not read from etcd: 100: Key not found (/skydns/config) [10]
2016/06/21 15:44:50 skydns: ready for queries on cluster.local. for tcp://0.0.0.0:53 [rcache 0]
2016/06/21 15:44:50 skydns: ready for queries on cluster.local. for udp://0.0.0.0:53 [rcache 0]

Note this too:

kubectl get pods --all-namespaces 
NAMESPACE     NAME                 READY     STATUS    RESTARTS   AGE
default       busybox              1/1       Running   0          17m
kube-system   kube-dns-v11-osikn   4/4       Running   0          18m

So I've got no problem with skydns.

I'm sure that the problem comes from kubelet, I've tried to remove /var/lib/kubelet and restart the entire cluster. I've tried to restart kubelete services before and after installing dns also. I changed docker configuration, removed "--dns" option afterwoard, and I've got the same behaviour: Docker + dns is ok, Kubelet gives a MissingClusterDNS error saying that kubelet has got no configured cluster dns.

So please... Help (one more time :) )

EDITS: - now kube2sky doesn't complain about <nil> api version forcing kube2sky option - I can force nslookup to use my sky DNS:

kubectl exec busybox -- nslookup kubernetes.default.svc.cluster.local 192.168.0.10
Server:    192.168.0.10
Address 1: 192.168.0.10

Name:      kubernetes.default.svc.cluster.local
Address 1: 192.168.0.1

But the "MissingClusterDNS" error remains on pod creation, as if kubelet doesn't the startup options "--cluster-dns" and "--cluster-domain"

@Brendan Burns:

kubectl get services --namespace=kube-system
NAME       CLUSTER-IP     EXTERNAL-IP   PORT(S)         AGE
kube-dns   192.168.0.10   <none>        53/UDP,53/TCP   12m