New to KubeDB? Please start here.

Using Custom RBAC resources

KubeDB (version 0.13.0 and higher) supports finer user control over role based access permissions provided to a Memcached instance. This tutorial will show you how to use KubeDB to run Memcached database with custom RBAC resources.

Before You Begin

At first, you need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using minikube.

Now, install KubeDB cli on your workstation and KubeDB operator in your cluster following the steps here.

To keep things isolated, this tutorial uses a separate namespace called demo throughout this tutorial.

$ kubectl create ns demo
namespace/demo created

Note: YAML files used in this tutorial are stored in docs/examples/memcached folder in GitHub repository kubedb/docs.

Overview

KubeDB allows users to provide custom RBAC resources, namely, ServiceAccount, Role, and RoleBinding for Memcached. This is provided via the spec.podTemplate.spec.serviceAccountName field in Memcached crd. If this field is left empty, the KubeDB operator will create a service account name matching Memcached crd name. Role and RoleBinding that provide necessary access permissions will also be generated automatically for this service account.

If a service account name is given, but there’s no existing service account by that name, the KubeDB operator will create one, and Role and RoleBinding that provide necessary access permissions will also be generated for this service account.

If a service account name is given, and there’s an existing service account by that name, the KubeDB operator will use that existing service account. Since this service account is not managed by KubeDB, users are responsible for providing necessary access permissions manually.

This guide will show you how to create custom Service Account, Role, and RoleBinding for a Memcached instance named quick-memcached to provide the bare minimum access permissions.

Custom RBAC for Memcached

At first, let’s create a Service Acoount in demo namespace.

$ kubectl create serviceaccount -n demo my-custom-serviceaccount
serviceaccount/my-custom-serviceaccount created

It should create a service account.

$ kubectl get serviceaccount -n demo my-custom-serviceaccount -o yaml
apiVersion: v1
kind: ServiceAccount
metadata:
  creationTimestamp: "2019-05-30T04:23:39Z"
  name: my-custom-serviceaccount
  namespace: demo
  resourceVersion: "21657"
  selfLink: /api/v1/namespaces/demo/serviceaccounts/myserviceaccount
  uid: b2ec2b05-8292-11e9-8d10-080027a8b217
secrets:
- name: myserviceaccount-token-t8zxd

Now, we need to create a role that has necessary access permissions for the Memcached instance named quick-memcached.

$ kubectl apply -f https://github.com/kubedb/docs/raw/v0.13.0-rc.0/docs/examples/memcached/custom-rbac/mc-custom-role.yaml
role.rbac.authorization.k8s.io/my-custom-role created

Below is the YAML for the Role we just created.

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: my-custom-role
  namespace: demo
rules:
- apiGroups:
  - policy
  resourceNames:
  - memcached-db
  resources:
  - podsecuritypolicies
  verbs:
  - use

This permission is required for Memcached pods running on PSP enabled clusters.

Now create a RoleBinding to bind this Role with the already created service account.

$ kubectl create rolebinding my-custom-rolebinding --role=my-custom-role --serviceaccount=demo:my-custom-serviceaccount --namespace=demo
rolebinding.rbac.authorization.k8s.io/my-custom-rolebinding created

It should bind my-custom-role and my-custom-serviceaccount successfully.

$ kubectl get rolebinding -n demo my-custom-rolebinding -o yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  creationTimestamp: "kubectl get rolebinding -n demo my-custom-rolebinding -o yaml"
  name: my-custom-rolebinding
  namespace: demo
  resourceVersion: "1405"
  selfLink: /apis/rbac.authorization.k8s.io/v1/namespaces/demo/rolebindings/my-custom-rolebinding
  uid: 123afc02-8297-11e9-8d10-080027a8b217
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: my-custom-role
subjects:
- kind: ServiceAccount
  name: my-custom-serviceaccount
  namespace: demo

Now, create a Memcached crd specifying spec.podTemplate.spec.serviceAccountName field to my-custom-serviceaccount.

$ kubectl apply -f https://github.com/kubedb/docs/raw/v0.13.0-rc.0/docs/examples/memcached/custom-rbac/mc-custom-db.yaml
memcached.kubedb.com/quick-memcached created

Below is the YAML for the Memcached crd we just created.

apiVersion: kubedb.com/v1alpha1
kind: Memcached
metadata:
  name: quick-memcached
  namespace: demo
spec:
  replicas: 3
  version: "1.5.4-v1"
  podTemplate:
    spec:
      serviceAccountName: my-custom-serviceaccount
      resources:
        limits:
          cpu: 500m
          memory: 128Mi
        requests:
          cpu: 250m
          memory: 64Mi
  terminationPolicy: DoNotTerminate

Now, wait a few minutes. the KubeDB operator will create necessary PVC, deployment, services, secret etc. If everything goes well, we should see that a pod with the name quick-memcached-0 has been created.

Check that the deployment’s pod is running

$ kubectl get pods -n demo
NAME                              READY   STATUS    RESTARTS   AGE
quick-memcached-d866d6d89-sdlkx   1/1     Running   0          5m52s
quick-memcached-d866d6d89-wpdz2   1/1     Running   0          5m52s
quick-memcached-d866d6d89-wvg7c   1/1     Running   0          5m52s

$ kubectl get pod -n demo quick-memcached-0
NAME                              READY     STATUS    RESTARTS   AGE
quick-memcached-d866d6d89-wvg7c   1/1       Running   0          14m

Reusing Service Account

An existing service account can be reused in another Memcached instance. No new access permission is required to run the new Memcached instance.

Now, create Memcached crd minute-memcached using the existing service account name my-custom-serviceaccount in the spec.podTemplate.spec.serviceAccountName field.

$ kubectl apply -f https://github.com/kubedb/docs/raw/v0.13.0-rc.0/docs/examples/memcached/custom-rbac/mc-custom-db-two.yaml
memcached.kubedb.com/quick-memcached created

Below is the YAML for the Memcached crd we just created.

apiVersion: kubedb.com/v1alpha1
kind: Memcached
metadata:
  name: minute-memcached
  namespace: demo
spec:
  replicas: 3
  version: "1.5.4-v1"
  podTemplate:
    spec:
      serviceAccountName: my-custom-serviceaccount
      resources:
        limits:
          cpu: 500m
          memory: 128Mi
        requests:
          cpu: 250m
          memory: 64Mi
  terminationPolicy: DoNotTerminate

Now, wait a few minutes. the KubeDB operator will create necessary PVC, deployment, services, secret etc. If everything goes well, we should see that a pod with the name minute-memcached-0 has been created.

Check that the deployment’s pod is running

$ kubectl get pods -n demo
NAME                              READY   STATUS    RESTARTS   AGE
minute-memcached-58798985f-47tm8  1/1     Running   0          5m52s
minute-memcached-58798985f-47tm8  1/1     Running   0          5m52s
minute-memcached-58798985f-47tm8  1/1     Running   0          5m52s

$ kubectl get pod -n demo minute-memcached-0
NAME                              READY     STATUS    RESTARTS   AGE
minute-memcached-58798985f-47tm8  1/1       Running   0          14m

Cleaning up

To cleanup the Kubernetes resources created by this tutorial, run:

kubectl patch -n demo mc/quick-memcached -p '{"spec":{"terminationPolicy":"WipeOut"}}' --type="merge"
kubectl delete -n demo mc/quick-memcached

kubectl patch -n demo mc/minute-memcached -p '{"spec":{"terminationPolicy":"WipeOut"}}' --type="merge"
kubectl delete -n demo mc/minute-memcached

kubectl delete -n demo role my-custom-role
kubectl delete -n demo rolebinding my-custom-rolebinding

kubectl delete sa -n demo my-custom-serviceaccount

kubectl delete ns demo

If you would like to uninstall the KubeDB operator, please follow the steps here.

Next Steps