9.7 KiB
Troubleshooting
Authentication to the Kubernetes API Server
A number of components are involved in the authentication process and the first step is to narrow down the source of the problem, namely whether it is a problem with service authentication or with the kubeconfig file. Both authentications must work:
+-------------+ service +------------+
| | authentication | |
+ apiserver +<-------------------+ ingress |
| | | controller |
+-------------+ +------------+
Service authentication
The Ingress controller needs information from apiserver. Therefore, authentication is required, which can be achieved in two different ways:
-
Service Account: This is recommended, because nothing has to be configured. The Ingress controller will use information provided by the system to communicate with the API server. See 'Service Account' section for details.
-
Kubeconfig file: In some Kubernetes environments service accounts are not available. In this case a manual configuration is required. The Ingress controller binary can be started with the
--kubeconfigflag. The value of the flag is a path to a file specifying how to connect to the API server. Using the--kubeconfigdoes not requires the flag--apiserver-host. The format of the file is identical to~/.kube/configwhich is used by kubectl to connect to the API server. See 'kubeconfig' section for details. -
Using the flag
--apiserver-host: Using this flag--apiserver-host=http://localhost:8080it is possible to specify an unsecure api server or reach a remote kubernetes cluster using kubectl proxy. Please do not use this approach in production.
In the diagram below you can see the full authentication flow with all options, starting with the browser on the lower left hand side.
Kubernetes Workstation
+---------------------------------------------------+ +------------------+
| | | |
| +-----------+ apiserver +------------+ | | +------------+ |
| | | proxy | | | | | | |
| | apiserver | | ingress | | | | ingress | |
| | | | controller | | | | controller | |
| | | | | | | | | |
| | | | | | | | | |
| | | service account/ | | | | | | |
| | | kubeconfig | | | | | | |
| | +<-------------------+ | | | | | |
| | | | | | | | | |
| +------+----+ kubeconfig +------+-----+ | | +------+-----+ |
| |<--------------------------------------------------------| |
| | | |
+---------------------------------------------------+ +------------------+
Service Account
If using a service account to connect to the API server, Dashboard expects the file
/var/run/secrets/kubernetes.io/serviceaccount/token to be present. It provides a secret
token that is required to authenticate with the API server.
Verify with the following commands:
# start a container that contains curl
$ kubectl run test --image=tutum/curl -- sleep 10000
# check that container is running
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
test-701078429-s5kca 1/1 Running 0 16s
# check if secret exists
$ kubectl exec test-701078429-s5kca ls /var/run/secrets/kubernetes.io/serviceaccount/
ca.crt
namespace
token
# get service IP of master
$ kubectl get services
NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes 10.0.0.1 <none> 443/TCP 1d
# check base connectivity from cluster inside
$ kubectl exec test-701078429-s5kca -- curl -k https://10.0.0.1
Unauthorized
# connect using tokens
$ TOKEN_VALUE=$(kubectl exec test-701078429-s5kca -- cat /var/run/secrets/kubernetes.io/serviceaccount/token)
$ echo $TOKEN_VALUE
eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3Mi....9A
$ kubectl exec test-701078429-s5kca -- curl --cacert /var/run/secrets/kubernetes.io/serviceaccount/ca.crt -H "Authorization: Bearer $TOKEN_VALUE" https://10.0.0.1
{
"paths": [
"/api",
"/api/v1",
"/apis",
"/apis/apps",
"/apis/apps/v1alpha1",
"/apis/authentication.k8s.io",
"/apis/authentication.k8s.io/v1beta1",
"/apis/authorization.k8s.io",
"/apis/authorization.k8s.io/v1beta1",
"/apis/autoscaling",
"/apis/autoscaling/v1",
"/apis/batch",
"/apis/batch/v1",
"/apis/batch/v2alpha1",
"/apis/certificates.k8s.io",
"/apis/certificates.k8s.io/v1alpha1",
"/apis/extensions",
"/apis/extensions/v1beta1",
"/apis/policy",
"/apis/policy/v1alpha1",
"/apis/rbac.authorization.k8s.io",
"/apis/rbac.authorization.k8s.io/v1alpha1",
"/apis/storage.k8s.io",
"/apis/storage.k8s.io/v1beta1",
"/healthz",
"/healthz/ping",
"/logs",
"/metrics",
"/swaggerapi/",
"/ui/",
"/version"
]
}
If it is not working, there are two possible reasons:
-
The contents of the tokens is invalid. Find the secret name with
kubectl get secrets | grep service-accountand delete it withkubectl delete secret <name>. It will automatically be recreated. -
You have a non-standard Kubernetes installation and the file containing the token may not be present. The API server will mount a volume containing this file, but only if the API server is configured to use the ServiceAccount admission controller. If you experience this error, verify that your API server is using the ServiceAccount admission controller. If you are configuring the API server by hand, you can set this with the
--admission-controlparameter. Please note that you should use other admission controllers as well. Before configuring this option, you should read about admission controllers.
More information:
kubeconfig
If you want to use a kubeconfig file for authentication, create a deployment file similar to the one below:
Note: the important part is the flag --kubeconfig=/etc/kubernetes/kubeconfig.yaml.
kind: Service
apiVersion: v1
metadata:
name: nginx-default-backend
labels:
k8s-addon: ingress-nginx.addons.k8s.io
spec:
ports:
- port: 80
targetPort: http
selector:
app: nginx-default-backend
---
kind: Deployment
apiVersion: extensions/v1beta1
metadata:
name: nginx-default-backend
labels:
k8s-addon: ingress-nginx.addons.k8s.io
spec:
replicas: 1
template:
metadata:
labels:
k8s-addon: ingress-nginx.addons.k8s.io
app: nginx-default-backend
spec:
terminationGracePeriodSeconds: 60
containers:
- name: default-http-backend
image: gcr.io/google_containers/defaultbackend:1.0
livenessProbe:
httpGet:
path: /healthz
port: 8080
scheme: HTTP
initialDelaySeconds: 30
timeoutSeconds: 5
resources:
limits:
cpu: 10m
memory: 20Mi
requests:
cpu: 10m
memory: 20Mi
ports:
- name: http
containerPort: 8080
protocol: TCP
---
kind: ConfigMap
apiVersion: v1
metadata:
name: ingress-nginx
labels:
k8s-addon: ingress-nginx.addons.k8s.io
---
kind: Service
apiVersion: v1
metadata:
name: ingress-nginx
labels:
k8s-addon: ingress-nginx.addons.k8s.io
spec:
type: LoadBalancer
selector:
app: ingress-nginx
ports:
- name: http
port: 80
targetPort: http
- name: https
port: 443
targetPort: https
---
kind: Deployment
apiVersion: extensions/v1beta1
metadata:
name: ingress-nginx
labels:
k8s-addon: ingress-nginx.addons.k8s.io
spec:
replicas: 1
template:
metadata:
labels:
app: ingress-nginx
k8s-addon: ingress-nginx.addons.k8s.io
spec:
terminationGracePeriodSeconds: 60
containers:
- image: gcr.io/google_containers/nginx-ingress-controller:0.9.0-beta.6
name: ingress-nginx
imagePullPolicy: Always
ports:
- name: http
containerPort: 80
protocol: TCP
- name: https
containerPort: 443
protocol: TCP
livenessProbe:
httpGet:
path: /healthz
port: 10254
scheme: HTTP
initialDelaySeconds: 30
timeoutSeconds: 5
env:
- name: POD_NAME
valueFrom:
fieldRef:
fieldPath: metadata.name
- name: POD_NAMESPACE
valueFrom:
fieldRef:
fieldPath: metadata.namespace
args:
- /nginx-ingress-controller
- --default-backend-service=$(POD_NAMESPACE)/nginx-default-backend
- --configmap=$(POD_NAMESPACE)/ingress-nginx
- --kubeconfig=/etc/kubernetes/kubeconfig.yaml
volumes:
- name: "kubeconfig"
hostPath:
path: "/etc/kubernetes/"