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Using Custom RBAC resources
KubeDB (version 0.13.0 and higher) supports finer user control over role based access permissions provided to a PostgreSQL instance. This tutorial will show you how to use KubeDB to run PostgreSQL instance 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 kind.
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/docs.
Overview
KubeDB allows users to provide custom RBAC resources, namely, ServiceAccount, Role, and RoleBinding for PostgreSQL. This is provided via the spec.podTemplate.spec.serviceAccountName field in Postgres CRD. If this field is left empty, the KubeDB operator will create a service account name matching Postgres 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 PostgreSQL instance named quick-postges to provide the bare minimum access permissions.
Custom RBAC for PostgreSQL
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 PostgreSQl Database named quick-postgres.
$ kubectl apply -f https://github.com/kubedb/docs/raw/v2021.04.16/docs/examples/postgres/custom-rbac/pg-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:
- 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
- apiGroups:
- policy
resourceNames:
- postgres-db
resources:
- podsecuritypolicies
verbs:
- use
Please note that resourceNames quick-postgres and quick-postgres-leader-lock are unique to quick-postgres PostgreSQL instance. Another database quick-postgres-2, for exmaple, will require these resourceNames to be quick-postgres-2, and quick-postgres-2-leader-lock.
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: "2019-05-30T04:54:56Z"
name: my-custom-rolebinding
namespace: demo
resourceVersion: "23944"
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 Postgres CRD specifying spec.podTemplate.spec.serviceAccountName field to my-custom-serviceaccount.
$ kubectl apply -f https://github.com/kubedb/docs/raw/v2021.04.16/docs/examples/postgres/custom-rbac/pg-custom-db.yaml
postgres.kubedb.com/quick-postgres created
Below is the YAML for the Postgres crd we just created.
apiVersion: kubedb.com/v1alpha2
kind: Postgres
metadata:
name: quick-postgres
namespace: demo
labels:
app.kubernetes.io/component: database
app.kubernetes.io/instance: quick-postgres
spec:
version: "13.2"
storageType: Durable
podTemplate:
spec:
serviceAccountName: my-custom-serviceaccount
storage:
storageClassName: "standard"
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 50Mi
Now, wait a few minutes. the KubeDB operator will create necessary PVC, statefulset, services, secret etc. If everything goes well, we should see that a pod with the name quick-postgres-0 has been created.
Check that the statefulset’s pod is running
$ kubectl get pod -n demo quick-postgres-0
NAME READY STATUS RESTARTS AGE
quick-postgres-0 1/1 Running 0 14m
Check the pod’s log to see if the database is ready
$ kubectl logs -f -n demo quick-postgres-0
I0705 12:05:51.697190 1 logs.go:19] FLAG: --alsologtostderr="false"
I0705 12:05:51.717485 1 logs.go:19] FLAG: --enable-analytics="true"
I0705 12:05:51.717543 1 logs.go:19] FLAG: --help="false"
I0705 12:05:51.717558 1 logs.go:19] FLAG: --log_backtrace_at=":0"
I0705 12:05:51.717566 1 logs.go:19] FLAG: --log_dir=""
I0705 12:05:51.717573 1 logs.go:19] FLAG: --logtostderr="false"
I0705 12:05:51.717581 1 logs.go:19] FLAG: --stderrthreshold="0"
I0705 12:05:51.717589 1 logs.go:19] FLAG: --v="0"
I0705 12:05:51.717597 1 logs.go:19] FLAG: --vmodule=""
We want "quick-postgres-0" as our leader
I0705 12:05:52.753464 1 leaderelection.go:175] attempting to acquire leader lease demo/quick-postgres-leader-lock...
I0705 12:05:52.822093 1 leaderelection.go:184] successfully acquired lease demo/quick-postgres-leader-lock
Got leadership, now do your jobs
Running as Primary
sh: locale: not found
WARNING: enabling "trust" authentication for local connections
You can change this by editing pg_hba.conf or using the option -A, or
--auth-local and --auth-host, the next time you run initdb.
ALTER ROLE
/scripts/primary/start.sh: ignoring /var/initdb/*
LOG: database system was shut down at 2018-07-05 12:07:51 UTC
LOG: MultiXact member wraparound protections are now enabled
LOG: database system is ready to accept connections
LOG: autovacuum launcher started
Once we see LOG: database system is ready to accept connections in the log, the database is ready.
Reusing Service Account
An existing service account can be reused in another Postgres Database. However, users need to create a new Role specific to that Postgres and bind it to the existing service account so that all the necessary access permissions are available to run the new Postgres Database.
For example, to reuse my-custom-serviceaccount in a new Database minute-postgres, create a role that has all the necessary access permissions for this PostgreSQl Database.
$ kubectl apply -f https://github.com/kubedb/docs/raw/v2021.04.16/docs/examples/postgres/custom-rbac/pg-custom-role-two.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-two
namespace: demo
rules:
- apiGroups:
- apps
resourceNames:
- miniute-postgres
resources:
- statefulsets
verbs:
- get
- apiGroups:
- ""
resourceNames:
- miniute-postgres-leader-lock
resources:
- configmaps
verbs:
- get
- update
Now create a RoleBinding to bind my-custom-role-two with the already created my-custom-serviceaccount.
$ kubectl create rolebinding my-custom-rolebinding-two --role=my-custom-role-two --serviceaccount=demo:my-custom-serviceaccount --namespace=demo
rolebinding.rbac.authorization.k8s.io/my-custom-rolebinding-two created
Now, create Postgres CRD minute-postgres 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/v2021.04.16/docs/examples/postgres/custom-rbac/pg-custom-db-two.yaml
postgres.kubedb.com/quick-postgres created
Below is the YAML for the Postgres crd we just created.
apiVersion: kubedb.com/v1alpha2
kind: Postgres
metadata:
name: minute-postgres
namespace: demo
labels:
app.kubernetes.io/component: database
app.kubernetes.io/instance: quick-postgres
spec:
version: "13.2"
storageType: Durable
podTemplate:
spec:
serviceAccountName: my-custom-serviceaccount
storage:
storageClassName: "standard"
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 50Mi
Now, wait a few minutes. the KubeDB operator will create necessary PVC, statefulset, services, secret etc. If everything goes well, we should see that a pod with the name minute-postgres-0 has been created.
Check that the statefulset’s pod is running
$ kubectl get pod -n demo minute-postgres-0
NAME READY STATUS RESTARTS AGE
minute-postgres-0 1/1 Running 0 14m
Check the pod’s log to see if the database is ready
$ kubectl logs -f -n demo minute-postgres-0
I0705 12:05:51.697190 1 logs.go:19] FLAG: --alsologtostderr="false"
I0705 12:05:51.717485 1 logs.go:19] FLAG: --enable-analytics="true"
I0705 12:05:51.717543 1 logs.go:19] FLAG: --help="false"
I0705 12:05:51.717558 1 logs.go:19] FLAG: --log_backtrace_at=":0"
I0705 12:05:51.717566 1 logs.go:19] FLAG: --log_dir=""
I0705 12:05:51.717573 1 logs.go:19] FLAG: --logtostderr="false"
I0705 12:05:51.717581 1 logs.go:19] FLAG: --stderrthreshold="0"
I0705 12:05:51.717589 1 logs.go:19] FLAG: --v="0"
I0705 12:05:51.717597 1 logs.go:19] FLAG: --vmodule=""
We want "minute-postgres-0" as our leader
I0705 12:05:52.753464 1 leaderelection.go:175] attempting to acquire leader lease demo/minute-postgres-leader-lock...
I0705 12:05:52.822093 1 leaderelection.go:184] successfully acquired lease demo/minute-postgres-leader-lock
Got leadership, now do your jobs
Running as Primary
sh: locale: not found
WARNING: enabling "trust" authentication for local connections
You can change this by editing pg_hba.conf or using the option -A, or
--auth-local and --auth-host, the next time you run initdb.
ALTER ROLE
/scripts/primary/start.sh: ignoring /var/initdb/*
LOG: database system was shut down at 2018-07-05 12:07:51 UTC
LOG: MultiXact member wraparound protections are now enabled
LOG: database system is ready to accept connections
LOG: autovacuum launcher started
LOG: database system is ready to accept connections in the log signifies that the database is running successfully.
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 patch -n demo pg/minute-postgres -p '{"spec":{"terminationPolicy":"WipeOut"}}' --type="merge"
kubectl delete -n demo pg/minute-postgres
kubectl delete -n demo role my-custom-role
kubectl delete -n demo role my-custom-role-two
kubectl delete -n demo rolebinding my-custom-rolebinding
kubectl delete -n demo rolebinding my-custom-rolebinding-two
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
- Learn about backup & restore of PostgreSQL databases using Stash.
- Learn about initializing PostgreSQL with Script.
- Want to setup PostgreSQL cluster? Check how to configure Highly Available PostgreSQL Cluster
- Monitor your PostgreSQL instance with KubeDB using built-in Prometheus.
- Monitor your PostgreSQL instance with KubeDB using Prometheus operator.
- Want to hack on KubeDB? Check our contribution guidelines.