Update create-cluster-kubeadm.md

[lanoxx]

Clarify in the documentation that a node must be joined before CoreDNS can start. I was mislead by the documentation into believing that the CoreDNS pods need to be running before I can join a node.

See also this discussion on Stackoverflow:
https://stackoverflow.com/questions/52609257/coredns-in-pending-state-in-kubernetus-cluster

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[neolit123]

@lanoxx
please sign the CLI if you want to contribute!

sorry but this is not correct:

It is necessary to join a node to the master otherwise the CoreDNS pods will be unable to start.

you can have a single-node cluster with the coredns pods running perfectly fine, so the issue here is something else.

I am using Kubernetes 1.12 and I am running into this isssue. I have setup Flannel using the kubectl apply syntax from the documentation but coredns pods are not starting up

there is a known bug in flannel with 1.12. try this command:
flannel-io/flannel#1045 (comment)

or you can try the weavenet plugin instead.

if you find bugs please report them in the kubernetes/kubeadm issue tracker.
thanks.

/close

[k8s-ci-robot]

@neolit123: Closing this PR.

In response to this:

@lanoxx
please sign the CLI if you want to contribute!

sorry but this is not correct:

It is necessary to join a node to the master otherwise the CoreDNS pods will be unable to start.

you can have a single-node cluster with the coredns pods running perfectly fine, so the issue here is something else.

I am using Kubernetes 1.12 and I am running into this isssue. I have setup Flannel using the kubectl apply syntax from the documentation but coredns pods are not starting up

there is a known bug in flannel with 1.12. try this command:
flannel-io/flannel#1045 (comment)

or you can try the weavenet plugin instead.

if you find bugs please report them in the kubernetes/kubeadm issue tracker.
thanks.

/close

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