kubectl proxy not working on Ubuntu LTS 18.04 - kubernetes

Question

I've installed Kubernetes on ubuntu 18.04 using this article. Everything is working fine and then I tried to install Kubernetes dashboard with these instructions.
Now when I am trying to run kubectl proxy then the dashboard is not cumming up and it gives following error message in the browser when trying to access it using default kubernetes-dashboard URL.
http://localhost:8001/api/v1/namespaces/kubernetes-dashboard/services/https:kubernetes-dashboard:/proxy/
{
"kind": "Status",
"apiVersion": "v1",
"metadata": {
},
"status": "Failure",
"message": "no endpoints available for service \"https:kubernetes-dashboard:\"",
"reason": "ServiceUnavailable",
"code": 503
}
Following commands give this output where kubernetes-dashboard shows status as CrashLoopBackOff
$> kubectl get pods --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE
default amazing-app-rs-59jt9 1/1 Running 5 23d
default amazing-app-rs-k6fg5 1/1 Running 5 23d
default amazing-app-rs-qd767 1/1 Running 5 23d
default amazingapp-one-deployment-57dddd6fb7-xdxlp 1/1 Running 5 23d
default nginx-86c57db685-vwfzf 1/1 Running 4 22d
kube-system coredns-6955765f44-nqphx 0/1 Running 14 25d
kube-system coredns-6955765f44-psdv4 0/1 Running 14 25d
kube-system etcd-master-node 1/1 Running 8 25d
kube-system kube-apiserver-master-node 1/1 Running 42 25d
kube-system kube-controller-manager-master-node 1/1 Running 11 25d
kube-system kube-flannel-ds-amd64-95lvl 1/1 Running 8 25d
kube-system kube-proxy-qcpqm 1/1 Running 8 25d
kube-system kube-scheduler-master-node 1/1 Running 11 25d
kubernetes-dashboard dashboard-metrics-scraper-7b64584c5c-kvz5d 1/1 Running 0 41m
kubernetes-dashboard kubernetes-dashboard-566f567dc7-w2sbk 0/1 CrashLoopBackOff 12 41m
$> kubectl get services --all-namespaces
NAMESPACE NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
default kubernetes ClusterIP ---------- <none> 443/TCP 25d
default nginx NodePort ---------- <none> 80:32188/TCP 22d
kube-system kube-dns ClusterIP ---------- <none> 53/UDP,53/TCP,9153/TCP 25d
kubernetes-dashboard dashboard-metrics-scraper ClusterIP ---------- <none> 8000/TCP 24d
kubernetes-dashboard kubernetes-dashboard ClusterIP ---------- <none> 443/TCP 24d
$ kubectl get services --all-namespaces
NAMESPACE NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
default kubernetes ClusterIP ====== <none> 443/TCP 25d
default nginx NodePort ====== <none> 80:32188/TCP 22d
kube-system kube-dns ClusterIP ====== <none> 53/UDP,53/TCP,9153/TCP 25d
kubernetes-dashboard dashboard-metrics-scraper ClusterIP ====== <none> 8000/TCP 24d
kubernetes-dashboard kubernetes-dashboard ClusterIP ====== <none> 443/TCP 24d
$ kubectl get events -n kubernetes-dashboard
LAST SEEN TYPE REASON OBJECT MESSAGE
24m Normal Pulling pod/kubernetes-dashboard-566f567dc7-w2sbk Pulling image "kubernetesui/dashboard:v2.0.0-rc2"
4m46s Warning BackOff pod/kubernetes-dashboard-566f567dc7-w2sbk Back-off restarting failed container
$ kubectl describe services kubernetes-dashboard -n kubernetes-dashboard
Name: kubernetes-dashboard
Namespace: kubernetes-dashboard
Labels: k8s-app=kubernetes-dashboard
Annotations: kubectl.kubernetes.io/last-applied-configuration:
{"apiVersion":"v1","kind":"Service","metadata":{"annotations":{},"labels":{"k8s-app":"kubernetes-dashboard"},"name":"kubernetes-dashboard"...
Selector: k8s-app=kubernetes-dashboard
Type: ClusterIP
IP: 10.96.241.62
Port: <unset> 443/TCP
TargetPort: 8443/TCP
Endpoints:
Session Affinity: None
Events: <none>
$ kubectl logs kubernetes-dashboard-566f567dc7-w2sbk -n kubernetes-dashboard
> 2020/01/29 16:00:34 Starting overwatch 2020/01/29 16:00:34 Using
> namespace: kubernetes-dashboard 2020/01/29 16:00:34 Using in-cluster
> config to connect to apiserver 2020/01/29 16:00:34 Using secret token
> for csrf signing 2020/01/29 16:00:34 Initializing csrf token from
> kubernetes-dashboard-csrf secret panic: Get
> https://10.96.0.1:443/api/v1/namespaces/kubernetes-dashboard/secrets/kubernetes-dashboard-csrf:
> dial tcp 10.96.0.1:443: i/o timeout
>
> goroutine 1 [running]:
> github.com/kubernetes/dashboard/src/app/backend/client/csrf.(*csrfTokenManager).init(0xc0003dac80)
> /home/travis/build/kubernetes/dashboard/src/app/backend/client/csrf/manager.go:40
> +0x3b4 github.com/kubernetes/dashboard/src/app/backend/client/csrf.NewCsrfTokenManager(...)
> /home/travis/build/kubernetes/dashboard/src/app/backend/client/csrf/manager.go:65
> github.com/kubernetes/dashboard/src/app/backend/client.(*clientManager).initCSRFKey(0xc000534200)
> /home/travis/build/kubernetes/dashboard/src/app/backend/client/manager.go:494
> +0xc7 github.com/kubernetes/dashboard/src/app/backend/client.(*clientManager).init(0xc000534200)
> /home/travis/build/kubernetes/dashboard/src/app/backend/client/manager.go:462
> +0x47 github.com/kubernetes/dashboard/src/app/backend/client.NewClientManager(...)
> /home/travis/build/kubernetes/dashboard/src/app/backend/client/manager.go:543
> main.main()
> /home/travis/build/kubernetes/dashboard/src/app/backend/dashboard.go:105
> +0x212
Any suggestions to fix this? Thanks in advance.

Answer 1

I noticed that the guide You used to install kubernetes cluster is missing one important part.
According to kubernetes documentation:
For flannel to work correctly, you must pass --pod-network-cidr=10.244.0.0/16 to kubeadm init.
Set /proc/sys/net/bridge/bridge-nf-call-iptables to 1 by running sysctl net.bridge.bridge-nf-call-iptables=1 to pass bridged IPv4 traffic to iptables’ chains. This is a requirement for some CNI plugins to work, for more information please see here.
Make sure that your firewall rules allow UDP ports 8285 and 8472 traffic for all hosts participating in the overlay network. see here .
Note that flannel works on amd64, arm, arm64, ppc64le and s390x under Linux. Windows (amd64) is claimed as supported in v0.11.0 but the usage is undocumented.
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/2140ac876ef134e0ed5af15c65e414cf26827915/Documentation/kube-flannel.yml
For more information about flannel, see the CoreOS flannel repository on GitHub .
To fix this:
I suggest using the command:
sysctl net.bridge.bridge-nf-call-iptables=1
And then reinstall flannel:
kubectl delete -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
Update: After verifying the the /proc/sys/net/bridge/bridge-nf-call-iptables value is 1 by default ubuntu-18-04-lts. So issue here is You need to access the dashboard locally.
If You are connected to Your master node via ssh. It could be possible to use -X flag with ssh in order to launch we browser via ForwardX11. Fortunately ubuntu-18-04-lts has it turned on by default.
ssh -X server
Then install local web browser like chromium.
sudo apt-get install chromium-browser
chromium-browser
And finally access the dashboard locally from node.
http://localhost:8001/api/v1/namespaces/kubernetes-dashboard/services/https:kubernetes-dashboard:/proxy/
Hope it helps.