Expose pod-network-cidr on kubeadm

[ozdanborne]

Getting Calico working in Kubernetes / Minikube can be tricky because you need to set the pod network cidr on multiple components (apiserver, controller-manager, and proxy) individually.

Kubeadm has made this easier by tying all three of those flags to a single "high-level" flag - --pod-network-cidr.

Now that minikube is using kubeadm under the hood, could we expose the --pod-network-cidr flag on it?

After a brief look at the code, I think we'd just need to template this value:

minikube/pkg/minikube/bootstrapper/kubeadm/templates.go

Line 84 in 3714bbd

podSubnet: ""

[tstromberg]

This sounds like a great idea, and I would be happy to approve any PR's that make it so. Help wanted!

[11janci]

I would like to take this if no objections

[hswong3i]

With my latest founding we could run minikube + flannel without kubeadm --pod-network-cidr, see

• https://github.com/alvistack/ansible-role-minikube/blob/afdf7b937a26e3e52e2cc68beab86cb6909022d4/tasks/main.yml#L90
• https://github.com/alvistack/ansible-role-minikube/blob/afdf7b937a26e3e52e2cc68beab86cb6909022d4/molecule/ubuntu-18.04/playbook.yml#L34

From https://github.com/coreos/flannel/blob/master/Documentation/troubleshooting.md#kubernetes-specific what we really needed are kubelet's --pod-cidr=<cidr> and controller-manager's --allocate-node-cidrs=true --cluster-cidr=<cidr>, so something like this:

minikube start \
    --extra-config=controller-manager.allocate-node-cidrs=true \
    --extra-config=controller-manager.cluster-cidr=10.233.64.0/18 \
    --extra-config=kubeadm.ignore-preflight-errors=FileContent--proc-sys-net-bridge-bridge-nf-call-iptables,SystemVerification \
    --extra-config=kubelet.cgroup-driver=systemd \
    --extra-config=kubelet.network-plugin=cni \
    --extra-config=kubelet.pod-cidr=10.233.64.0/18 \
    --extra-config=kubelet.resolv-conf=/run/systemd/resolve/resolv.conf \
    --kubernetes-version=v1.14.1 \
    --network-plugin=cni \
    --vm-driver=none

curl -skL https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml > /tmp/kube-flannel.yml
sed -i 's/10.244.0.0\/16/10.233.64.0\/18/g' /tmp/kube-flannel.yml
kubectl apply -f /tmp/kube-flannel.yml