capsule/docs/operator/use-cases/custom-resources.md

Create Custom Resources

Capsule operator the admin permissions to the tenant's users but only limited to their namespaces. To achieve that, it assign the ClusterRole admin to the tenant owner. This ClusterRole does not permit the installation of custom resources in the namespaces.

In order to leave the tenant owner to create Custom Resources in their namespaces, the cluster admin defines a proper Cluster Role. For example:

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: argoproj-provisioner
rules:
- apiGroups:
  - argoproj.io
  resources:
  - applications
  - appprojects
  verbs:
  - create
  - get
  - list
  - watch
  - update
  - patch
  - delete

Bill can assign this role to any namespace in the Alice's tenant by setting it in the tenant manifest:

apiVersion: capsule.clastix.io/v1alpha1
kind: Tenant
metadata:
  name: oil
spec:
  owner:
    name: alice
    kind: User
  additionalRoleBindings:
    - clusterRoleName: 'argoproj-provisioner'
      subjects:
        - apiGroup: rbac.authorization.k8s.io
          kind: User
          name: alice
        - apiGroup: rbac.authorization.k8s.io
          kind: User
          name: joe

or in case of Group type owners:

apiVersion: capsule.clastix.io/v1alpha1
kind: Tenant
metadata:
  name: oil
spec:
  owner:
    name: alice
    kind: User
  additionalRoleBindings:
    - clusterRoleName: 'argoproj-provisioner'
      subjects:
        - apiGroup: rbac.authorization.k8s.io
          kind: User
          name: alice

With the given specification, Capsule will ensure that all Alice's namespaces will contain a RoleBinding for the specified Cluster Role. For example, in the oil-production namespace, Alice will see:

kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: capsule-oil-argoproj-provisioner
  namespace: oil-production
subjects:
  - kind: User
    apiGroup: rbac.authorization.k8s.io
    name: alice
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: argoproj-provisioner

With the above example, Capsule is leaving the tenant owner to create namespaced custom resources.

Nota bene: a tenant owner having the admin scope on its namespaces only, does not have the permission to create Custom Resources Definitions (CRDs) because this requires a cluster admin permission level. Only Bill, the cluster admin, can create CRDs. This is a known limitation of any multi-tenancy environment based on a single Kubernetes cluster.

What’s next

See how Bill, the cluster admin, can set taints on the Alice's namespaces. Taint namespaces.