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Access & Expose vCluster

Access vCluster​

There are multiple ways how you can access a vCluster with an external application like kubectl.

Connect Directly using the CLI​

Please make sure to install the vCluster CLI.

brew install loft-sh/tap/vcluster

The binaries in the tap are signed using the Sigstore framework for enhanced security.

Confirm that you've installed the correct version of the vCluster CLI.

vcluster --version
# Connect and switch the current context to the vCluster
vcluster connect my-vcluster -n my-vcluster

# Print the kube-config
vcluster connect my-vcluster --print

# Switch back context
vcluster disconnect

# Create a separate kube config to use instead of changing the current context
vcluster connect my-vcluster --update-current=false

# Execute a command directly with vCluster context without changing the current context
vcluster connect my-vcluster -- kubectl get namespaces
vcluster connect my-vcluster -- bash

Depending on if the vCluster was created within a local Kubernetes cluster or with the --expose flag, the CLI will either start port-forwarding or create a context that can be used directly.

If you have manually exposed the vCluster, you can specify the domain where the vCluster is reachable via the --server flag:

# Will create a kube context that uses https://my-domain.org as endpoint
vcluster connect my-vcluster -n my-vcluster --server my-domain.org

Connect via Service Accounts​

By default, vCluster will update the current kubeconfig to access the vCluster that contains the default admin client certificate and client key to authenticate to the vCluster. This means that all kubeconfig files generated will have cluster admin access within the vCluster.

Often this might not be desired. Instead of giving a user admin access to the virtual cluster, you can also use service account authentication to the virtual cluster. Let's say we want to create a kubeconfig file that only has view access in the virtual cluster. Then you would create a new service account inside the vCluster and assign it the cluster role view via a cluster role binding. Then we would generate a service account token and use that instead of the client-cert and client-key inside the kubeconfig.

vcluster connect my-vcluster -n my-vcluster --service-account kube-system/my-user --cluster-role view

# OR: create a kube context for a cluster admin
vcluster connect my-vcluster -n my-vcluster --service-account kube-system/my-user --cluster-role cluster-admin

# OR: create a kube context that expires after an hour
vcluster connect my-vcluster -n my-vcluster --service-account kube-system/my-user --cluster-role view --token-expiration 3600

This will create a kube context similar to this as well as create the needed service account and cluster role binding:

apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: LS0t...
    server: https://localhost:8443
  name: local
contexts:
- context:
    cluster: local
    namespace: default
    user: user
  name: Default
current-context: Default
kind: Config
preferences: {}
users:
- name: user
  user:
    token: eyJhbGc...

As you can see the service account token is used in this kubeconfig here instead of the client-cert and client-key that is used by default. Trying to create a namespace with this config will yield:

export KUBECONFIG=kubeconfig.yaml

# This will work as we have view access
kubectl get namespaces

# This won't work
kubectl create namespace test
Error from server (Forbidden): namespaces is forbidden: User "system:serviceaccount:kube-system:my-user" cannot create resource "namespaces" in API group "" at the cluster scope

You can replace the token field in the kubeconfig with any other service account token from inside the vCluster to act as this service account against the vCluster. For more information about service accounts and tokens, please refer to the official Kubernetes documentation.

Retrieving the kubeconfig from the vCluster secret​

There might be cases where connecting to a vCluster with the CLI is not feasible or the CLI cannot be installed. For such cases, you can retrieve the vCluster kubeconfig from a secret that is created automatically in the vCluster namespace.

The secret is prefixed with vc- and ends with the vCluster name, so a vCluster called my-vcluster in namespace test would create a secret called vc-my-vcluster in the namespace test. You can retrieve the kubeconfig after the vCluster has started via:

kubectl get secret vc-my-vcluster -n test --template={{.data.config}} | base64 -D

The secret will hold a kubeconfig in this format:

apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: LS0t...
    server: https://localhost:8443
  name: local
contexts:
- context:
    cluster: local
    namespace: default
    user: user
  name: Default
current-context: Default
kind: Config
users:
- name: user
  user:
    client-certificate-data: LS0tLS...
    client-key-data: LS0tLS...

By default, the server https://localhost:8443 is used that would work if you port forward the vCluster with:

kubectl port-forward my-vcluster-0 -n test 8443
tip

With the syncer flag --out-kube-config-secret-namespace you can specify a different namespace where the kubeconfig secret should be created in. Keep in mind that you have to manually apply RBAC permissions for the vCluster to allow creation and retrieving of secrets in that namespace.

Access vCluster Externally​

If you have exposed the vCluster, you can also tell the vCluster to create the kubeconfig secret with another server endpoint through the exportKubeConfig flag.

For example, if you want to expose a vCluster at https://my-domain.org, you can create a vcluster.yaml like this:

# Make sure vCluster will sign the server certs for my-domain.org
# and use it in the generated kube config secret.
controlPlane:
  # distro: (update distro details as per your configurations)
  #   k3s:
  #     enabled: true
  proxy:
    extraSANs:
    - my-domain.org
  statefulSet:
    scheduling:
      podManagementPolicy: OrderedReady
exportKubeConfig:
  server: https://my-domain.org:443

Then you can create or upgrade the vCluster with:

vcluster create my-vcluster -n my-vcluster --upgrade --connect=false -f values.yaml

Wait until the vCluster has started and you can retrieve the kubeconfig via:

kubectl get secret vc-my-vcluster -n my-vcluster --template={{.data.config}} | base64 -D

Expose vCluster​

By default, vCluster is only reachable via port-forwarding in remote clusters. However, this means that you need access to the host cluster, where the vCluster is running, in order to access it. To directly access vCluster without port-forwarding, you can use one of the following methods.

Local Kubernetes Clusters

If you are using a local Kubernetes cluster, such as docker-desktop, rancher-desktop, KinD or minikube, vCluster will automatically connect to it without the need of port-forwarding.

An Ingress Controller with SSL passthrough support will provide the best user experience, but there is a workaround if this feature is not natively supported.

Make sure your ingress controller is installed and healthy on the cluster that will host your virtual clusters. Create the following ingress.yaml for a vCluster called my-vcluster in the namespace my-vcluster:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    # We need the ingress to pass through ssl traffic to the vCluster
    # This only works for the nginx-ingress (enable via --enable-ssl-passthrough
    # https://kubernetes.github.io/ingress-nginx/user-guide/tls/#ssl-passthrough )
    # for other ingress controllers please check their respective documentation.
    nginx.ingress.kubernetes.io/backend-protocol: HTTPS
    nginx.ingress.kubernetes.io/ssl-passthrough: "true"
    nginx.ingress.kubernetes.io/ssl-redirect: "true"
  name: vcluster-ingress
  namespace: my-vcluster
spec:
  ingressClassName: nginx # use your ingress class name
  rules:
  - host: my-vcluster.example.com
    http:
      paths:
      - backend:
          service:
            name: my-vcluster
            port:
              number: 443
        path: /
        pathType: ImplementationSpecific

Create the resource in the namespace via:

kubectl apply -f ingress.yaml
Enable SSL Passthrough Feature

If you are using the ingress nginx controller, please make sure you have enabled the SSL passthrough feature as it is disabled by default.

To enable the SSL Passthrough Feature you can edit the nginx ingress deployment within the nginx namespace. The option that needs to be added is - --enable-ssl-passthrough under the container args within spec. It should end up looking something like:

    spec:
      containers:
      - args:
        - /nginx-ingress-controller
        - --publish-service=$(POD_NAMESPACE)/ingress-nginx-controller
        - --election-id=ingress-nginx-leader
        - --controller-class=k8s.io/ingress-nginx
        - --ingress-class=nginx
        - --configmap=$(POD_NAMESPACE)/ingress-nginx-controller
        - --validating-webhook=:8443
        - --validating-webhook-certificate=/usr/local/certificates/cert
        - --validating-webhook-key=/usr/local/certificates/key
        - --enable-ssl-passthrough
SSL Passthrough required

In order for this ingress to work correctly, you will need to enable SSL passthrough as TLS termination has to happen at the vCluster level and not ingress controller level. If you cannot do that, please take a look below for using an ingress without ssl passthrough.

Now create a vcluster.yaml to create the vCluster with:

controlPlane:
  proxy:
    extraSANs:
    - my-vcluster.example.com

Create the virtual cluster with:

vcluster create my-vcluster -n my-vcluster --connect=false -f values.yaml

Retrieve the kube config via:

vcluster connect my-vcluster -n my-vcluster --print --server=https://my-vcluster.example.com > kubeconfig.yaml

Access the vCluster:

export KUBECONFIG=./kubeconfig.yaml

# Run any kubectl command
kubectl get ns