As of release 1.7 Dashboard supports user authentication based on:

• Authorization: Bearer <token> header passed in every request to Dashboard. Supported from release 1.6. Has the highest priority. If present, login view will not be shown.
• Bearer Token that can be used on Dashboard login view.
• Username/password that can be used on Dashboard login view.
• Kubeconfig file that can be used on Dashboard login view.

— Dashboard on Github

Token

Here Token can be Static Token, Service Account Token, OpenID Connect Token from Kubernetes Authenticating, but not the kubeadm Bootstrap Token.

With kubectl, we can get an service account (eg. deployment controller) created in kubernetes by default.

$ kubectl -n kube-system get secret# All secrets with type 'kubernetes.io/service-account-token' will allow to log in.# Note that they have different privileges.NAME                                     TYPE                                  DATA      AGEdeployment-controller-token-frsqj        kubernetes.io/service-account-token   3         22h$ kubectl -n kube-system describe secret deployment-controller-token-frsqjName:         deployment-controller-token-frsqjNamespace:    kube-systemLabels:       <none>Annotations:  kubernetes.io/service-account.name=deployment-controller              kubernetes.io/service-account.uid=64735958-ae9f-11e7-90d5-02420ac00002Type:  kubernetes.io/service-account-tokenData====ca.crt:     1025 bytesnamespace:  11 bytestoken:      eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.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.OqFc4CE1Kh6T3BTCR4XxDZR8gaF1MvH4M3ZHZeCGfO-sw-D0gp826vGPHr_0M66SkGaOmlsVHmP7zmTi-SJ3NCdVO5viHaVUwPJ62hx88_JPmSfD0KJJh6G5QokKfiO0WlGN7L1GgiZj18zgXVYaJShlBSz5qGRuGf0s1jy9KOBt9slAN5xQ9_b88amym2GIXoFyBsqymt5H-iMQaGP35tbRpewKKtly9LzIdrO23bDiZ1voc5QZeAZIWrizzjPY5HPM1qOqacaY9DcGc7akh98eBJG_4vZqH2gKy76fMf0yInFTeNKr45_6fWt8gRM77DQmPwb3hbrjWXe1VvXX_g

Kubeconfig

The dashboard needs the user in the kubeconfig file to have either username & password or token, but admin.conf only has client-certificate. You can edit the config file to add the token that was extracted using the method above.

$ kubectl config set-credentials cluster-admin --token=bearer_token

Alternative (Not recommended for Production)

Here are two ways to bypass the authentication, but use for caution.

Deploy dashboard with HTTP

$ kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/master/src/deploy/alternative/kubernetes-dashboard.yaml

Dashboard can be loaded at http://localhost:8001/ui with kubectl proxy.

Granting admin privileges to Dashboard's Service Account

$ cat <<EOF | kubectl create -f -apiVersion: rbac.authorization.k8s.io/v1beta1kind: ClusterRoleBindingmetadata:  name: kubernetes-dashboard  labels:    k8s-app: kubernetes-dashboardroleRef:  apiGroup: rbac.authorization.k8s.io  kind: ClusterRole  name: cluster-adminsubjects:- kind: ServiceAccount  name: kubernetes-dashboard  namespace: kube-systemEOF

Afterwards you can use Skip option on login page to access Dashboard.

If you are using dashboard version v1.10.1 or later, you must also add --enable-skip-login to the deployment's command line arguments. You can do so by adding it to the args in kubectl edit deployment/kubernetes-dashboard --namespace=kube-system.

Example:

      containers:      - args:        - --auto-generate-certificates        - --enable-skip-login            # <-- add this line        image: k8s.gcr.io/kubernetes-dashboard-amd64:v1.10.1

TL;DR

To get the token in a single oneliner:

kubectl -n kube-system describe secret $(kubectl -n kube-system get secret | awk '/^deployment-controller-token-/{print $1}') | awk '$1=="token:"{print $2}'

This assumes that your ~/.kube/config is present and valid. And also that kubectl config get-contexts indicates that you are using the correct context (cluster and namespace) for the dashboard you are logging into.

Explanation

I derived this answer from what I learned from @silverfox's answer. That is a very informative write up. Unfortunately it falls short of telling you how to actually put the information into practice. Maybe I've been doing DevOps too long, but I think in shell. It's much more difficult for me to learn or teach in English.

Here is that oneliner with line breaks and indents for readability:

kubectl -n kube-system describe secret $(  kubectl -n kube-system get secret | \  awk '/^deployment-controller-token-/{print $1}') | \awk '$1=="token:"{print $2}'

There are 4 distinct commands and they get called in this order:

• Line 2 - This is the first command from @silverfox's Token section.
• Line 3 - Print only the first field of the line beginning with deployment-controller-token- (which is the pod name)
• Line 1 - This is the second command from @silverfox's Token section.
• Line 5 - Print only the second field of the line whose first field is "token:"

If you don't want to grant admin permission to dashboard service account, you can create cluster admin service account.

$ kubectl create serviceaccount cluster-admin-dashboard-sa$ kubectl create clusterrolebinding cluster-admin-dashboard-sa \  --clusterrole=cluster-admin \  --serviceaccount=default:cluster-admin-dashboard-sa

And then, you can use the token of just created cluster admin service account.

$ kubectl get secret | grep cluster-admin-dashboard-sacluster-admin-dashboard-sa-token-6xm8l   kubernetes.io/service-account-token   3         18m$ kubectl describe secret cluster-admin-dashboard-sa-token-6xm8l

I quoted it from giantswarm guide - https://docs.giantswarm.io/guides/install-kubernetes-dashboard/