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documentation / Installation

Installation

The Kyverno policy engine runs as an admission webhook and requires a CA-signed certificate and key to setup secure TLS communication with the kube-apiserver (the CA can be self-signed).

There are 2 ways to configure the secure communications link between Kyverno and the kube-apiserver:

Option 1: Use kube-controller-manager to generate a CA-signed certificate

Kyverno can request a CA signed certificate-key pair from kube-controller-manager. This method requires that the kube-controller-manager is configured to act as a certificate signer. To verify that this option is enabled for your cluster, check the command-line args for the kube-controller-manager. If --cluster-signing-cert-file and --cluster-signing-key-file are passed to the controller manager with paths to your CA's key-pair, then you can proceed to install Kyverno using this method.

To install Kyverno in a cluster that supports certificate signing, run the following command on a host with kubectl cluster-admin access:

kubectl create -f https://github.com/nirmata/kyverno/raw/master/definitions/install.yaml

To check the Kyverno controller status, run the command:

kubectl get pods -n kyverno

If the Kyverno controller is not running, you can check its status and logs for errors:

kubectl describe pod <kyverno-pod-name> -n kyverno
kubectl logs <kyverno-pod-name> -n kyverno

Option 2: Use your own CA-signed certificate

You can install your own CA-signed certificate, or generate a self-signed CA and use it to sign a certifcate. Once you have a CA and X.509 certificate-key pair, you can install these as Kubernetes secrets in your cluster. If Kyverno finds these secrets, it uses them. Otherwise it will request the kube-controller-manager to generate a certificate (see Option 1 above).

1. Generate a self-signed CA and signed certificate-key pair

Note: using a separate self-signed root CA is difficult to manage and not recommeded for production use.

If you already have a CA and a signed certificate, you can directly proceed to Step 2.

Here are the commands to create a self-signed root CA, and generate a signed certificate and key using openssl (you can customize the certificate attributes for your deployment):

openssl genrsa -out rootCA.key 4096
openssl req -x509 -new -nodes -key rootCA.key -sha256 -days 1024 -out rootCA.crt  -subj "/C=US/ST=test/L=test /O=test /OU=PIB/CN=*.kyverno.svc/emailAddress=test@test.com"
openssl genrsa -out webhook.key 4096
openssl req -new -key webhook.key -out webhook.csr  -subj "/C=US/ST=test /L=test /O=test /OU=PIB/CN=kyverno-svc.kyverno.svc/emailAddress=test@test.com"
openssl x509 -req -in webhook.csr -CA rootCA.crt -CAkey rootCA.key -CAcreateserial -out webhook.crt -days 1024 -sha256

Among the files that will be generated, you can use the following files to create Kubernetes secrets:

  • rootCA.crt
  • webhooks.crt
  • webhooks.key

2. Configure secrets for the CA and TLS certificate-key pair

To create the required secrets, use the following commands (do not change the secret names):

kubectl create ns kyverno
kubectl -n kyverno create secret tls kyverno-svc.kyverno.svc.kyverno-tls-pair --cert=webhook.crt --key=webhook.key
kubectl annotate secret kyverno-svc.kyverno.svc.kyverno-tls-pair -n kyverno self-signed-cert=true
kubectl -n kyverno create secret generic kyverno-svc.kyverno.svc.kyverno-tls-ca --from-file=rootCA.crt

NOTE: The annotation on the TLS pair secret is used by Kyverno to identify the use of self-signed certificates and checks for the required root CA secret

Secret Data Content
kyverno-svc.kyverno.svc.kyverno-tls-pair rootCA.crt root CA used to sign the certificate
kyverno-svc.kyverno.svc.kyverno-tls-ca tls.key & tls.crt key and signed certificate

Kyverno uses secrets created above to setup TLS communication with the kube-apiserver and specify the CA bundle to be used to validate the webhook server's certificate in the admission webhook configurations.

3. Install Kyverno

To install a specific version, change the image tag with git tag in install.yaml.

e.g., change image tag from latest to the specific tag v0.3.0.

spec:
  containers:
    - name: kyverno
      # image: nirmata/kyverno:latest
      image: nirmata/kyverno:v0.3.0
kubectl create -f https://github.com/nirmata/kyverno/raw/master/definitions/install.yaml

To check the Kyverno controller status, run the command:

kubectl get pods -n kyverno

If the Kyverno controller is not running, you can check its status and logs for errors:

kubectl describe pod <kyverno-pod-name> -n kyverno
kubectl logs <kyverno-pod-name> -n kyverno

Here is a script that generates a self-signed CA, a TLS certificate-key pair, and the corresponding kubernetes secrets: helper script

Installing outside of the cluster (debug mode)

To build Kyverno in a development environment see: https://github.com/nirmata/kyverno/wiki/Building

To run controller in this mode you should prepare TLS key/certificate pair for debug webhook, then start controller with kubeconfig and the server address.

  1. Run scripts/deploy-controller-debug.sh --service=localhost --serverIP=<server_IP>, where <server_IP> is the IP address of the host where controller runs. This scripts will generate TLS certificate for debug webhook server and register this webhook in the cluster. Also it registers CustomResource Policy.
  2. Start the controller using the following command: sudo kyverno --kubeconfig=~/.kube/config --serverIP=<server_IP>

Try Kyverno without a Kubernetes cluster

The Kyverno CLI allows you to write and test policies without installing Kyverno in a Kubernetes cluster. Some features are not supported without a Kubernetes cluster.

Filter kuberenetes resources that admission webhook should not process

The admission webhook checks if a policy is applicable on all admission requests. The kubernetes kinds that are not be processed can be filtered by using the command line argument 'filterKind'.

By default we have specified Nodes, Events, APIService & SubjectAccessReview as the kinds to be skipped in the install.yaml.


Read Next >> Writing Policies

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