Use cluster-dns IP setup by kubeadm

[vijaykatam]

Removed hardcoded cluster-dns IP 10.96.0.10, this allows kubelet to use clusterDNS configured by kubeadm in /var/lib/kubelet/config.yaml

Tested by starting minikube with --service-cluster-ip-range=100.64.0.0/13 and verifying DNS resolution works.

/etc/systemd/system/kubelet.service.d/10-kubeadm.conf

[Unit]
Wants=docker.socket

[Service]
ExecStart=
ExecStart=/var/lib/minikube/binaries/v1.17.0/kubelet --authorization-mode=Webhook --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --cgroup-driver='cgroupfs' --client-ca-file=/v
ar/lib/minikube/certs/ca.crt --cluster-domain=cluster.local --config=/var/lib/kubelet/config.yaml --container-runtime=docker --fail-swap-on=false --hostname-override=minikube --kubeconfig=/e
tc/kubernetes/kubelet.conf --node-ip=192.168.64.7 --pod-manifest-path=/etc/kubernetes/manifests

[Install]

DNS resolution test

kubectl run -i --tty --rm busybox --image=busybox --restart=Never -- sh
If you don't see a command prompt, try pressing enter.
/ # nslookup kubernetes.io
Server:		100.64.0.10
Address:	100.64.0.10:53

Non-authoritative answer:
Name:	kubernetes.io
Address: 147.75.40.148

Fixes: #5727

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[k8s-ci-robot]

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[minikube-bot]

Can one of the admins verify this patch?

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[medyagh]

@vijaykatam interesting PR ! I am curious if this will break anyone !
could we use the current behaviour if the user didn't pass a an extra settings?

btw the unit tests datas need to be updated for the PR.

[medyagh]

/ok-to-test

[minikube-pr-bot]

Error: running mkcmp: exit status 1

[vijaykatam]

could we use the current behaviour if the user didn't pass a an extra settings?

@medyagh if user didn't pass --service-cluster-ip-range the default behavior of kubeadm is to use 10.96.0.10, see https://github.com/kubernetes/kubernetes/blob/master/cmd/kubeadm/app/componentconfigs/kubelet.go#L108-L112. Since /var/lib/kubelet/config.yaml is already being passed in the kubelet drop-in, I guess always use clusterDNS specified by kubeadm?

[vijaykatam]

I updated unit test setup data and they pass now. Integration test failures seem unrelated to this change.

[medyagh]

Thanks @vijaykatam I will investigate, please run make lint
there are lint issues in travis.

[vijaykatam]

@medyagh I didn't see lint errors running make lint. Travis build failure is not due to lint error

$ travis_setup_go
I don't have any idea what to do with '1.13.4'.
  (using download type 'auto')
Failed to run gimme
The command "travis_setup_go" failed and exited with 86 during .

I rebased with latest from master and I see 2 lint errors unrelated to my change which I am fixing.

pkg/minikube/cluster/start.go:189: File is not `goimports`-ed (goimports)
  if driver.BareMetal(h.Driver.DriverName()) {
pkg/addons/addons.go:211:2: printf: Infof format %s has arg command of wrong type *os/exec.Cmd (govet)
	glog.Infof("Running: %s", command)
	^

[codecov-io]

Codecov Report

Merging #6472 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master    #6472   +/-   ##
=======================================
  Coverage   37.96%   37.96%           
=======================================
  Files         138      138           
  Lines        8698     8698           
=======================================
  Hits         3302     3302           
  Misses       4980     4980           
  Partials      416      416

Impacted Files	Coverage Δ
pkg/minikube/bootstrapper/bsutil/versions.go	81.81% <ø> (ø)	⬆️
pkg/addons/addons.go	45.96% <0%> (ø)	⬆️
pkg/minikube/cluster/start.go	52.33% <0%> (ø)	⬆️

[tstromberg]

Thank you!