New to KubeDB? Please start here.

RBAC Permissions for Postgres

If RBAC is enabled in clusters, some PostgreSQL specific RBAC permissions are required. These permissions are required for Leader Election process of PostgreSQL clustering.

Here is the list of additional permissions required by StatefulSet of Postgres:

Kubernetes ResourceResource NamesPermission required
statefulsets{postgres-name}get
podslist, patch
configmapscreate
configmaps{postgres-name}-leader-lockget, update

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/postgres folder in GitHub repository kubedb/cli.

Create a PostgreSQL database

Below is the Postgres object created in this tutorial.

apiVersion: kubedb.com/v1alpha1
kind: Postgres
metadata:
  name: quick-postgres
  namespace: demo
spec:
  version: "10.2-v2"
  storageType: Durable
  storage:
    storageClassName: "standard"
    accessModes:
    - ReadWriteOnce
    resources:
      requests:
        storage: 1Gi
  terminationPolicy: DoNotTerminate

Create above Postgres object with following command

$ kubectl create -f https://raw.githubusercontent.com/kubedb/cli/0.11.0/docs/examples/postgres/quickstart/quick-postgres.yaml
postgres.kubedb.com/quick-postgres created

When this Postgres object is created, KubeDB operator creates Role, ServiceAccount and RoleBinding with the matching PostgreSQL name and uses that ServiceAccount name in the corresponding StatefulSet.

Let’s see what KubeDB operator has created for additional RBAC permission

Role

KubeDB operator create a Role object quick-postgres in same namespace as Postgres object.

$ kubectl get role -n demo quick-postgres -o yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  creationTimestamp: "2019-02-07T11:08:56Z"
  name: quick-postgres
  namespace: demo
  ownerReferences:
  - apiVersion: kubedb.com/v1alpha1
    blockOwnerDeletion: false
    kind: Postgres
    name: quick-postgres
    uid: c2f4d63c-2ac8-11e9-9d44-080027154f61
  resourceVersion: "39422"
  selfLink: /apis/rbac.authorization.k8s.io/v1/namespaces/demo/roles/quick-postgres
  uid: c31e7f33-2ac8-11e9-9d44-080027154f61
rules:
- apiGroups:
  - apps
  resourceNames:
  - quick-postgres
  resources:
  - statefulsets
  verbs:
  - get
- apiGroups:
  - ""
  resources:
  - pods
  verbs:
  - list
  - patch
- apiGroups:
  - ""
  resources:
  - configmaps
  verbs:
  - create
- apiGroups:
  - ""
  resourceNames:
  - quick-postgres-leader-lock
  resources:
  - configmaps
  verbs:
  - get
  - update

ServiceAccount

KubeDB operator create a ServiceAccount object quick-postgres in same namespace as Postgres object.

$ kubectl get serviceaccount -n demo quick-postgres -o yaml
apiVersion: v1
kind: ServiceAccount
metadata:
  creationTimestamp: "2019-02-07T11:08:56Z"
  name: quick-postgres
  namespace: demo
  ownerReferences:
  - apiVersion: kubedb.com/v1alpha1
    blockOwnerDeletion: false
    kind: Postgres
    name: quick-postgres
    uid: c2f4d63c-2ac8-11e9-9d44-080027154f61
  resourceVersion: "39425"
  selfLink: /api/v1/namespaces/demo/serviceaccounts/quick-postgres
  uid: c31fd2b1-2ac8-11e9-9d44-080027154f61
secrets:
- name: quick-postgres-token-b6zk2

This ServiceAccount is used in StatefulSet created for Postgres object.

RoleBinding

KubeDB operator create a RoleBinding object quick-postgres in same namespace as Postgres object.

$ kubectl get rolebinding -n demo quick-postgres -o yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  creationTimestamp: "2019-02-07T11:08:56Z"
  name: quick-postgres
  namespace: demo
  ownerReferences:
  - apiVersion: kubedb.com/v1alpha1
    blockOwnerDeletion: false
    kind: Postgres
    name: quick-postgres
    uid: c2f4d63c-2ac8-11e9-9d44-080027154f61
  resourceVersion: "39426"
  selfLink: /apis/rbac.authorization.k8s.io/v1/namespaces/demo/rolebindings/quick-postgres
  uid: c3231382-2ac8-11e9-9d44-080027154f61
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: Role
  name: quick-postgres
subjects:
- kind: ServiceAccount
  name: quick-postgres
  namespace: demo

This object binds Role quick-postgres with ServiceAccount quick-postgres.

Leader Election process get access to Kubernetes API using these RBAC permissions.

Cleaning up

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

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

kubectl delete ns demo