Reference Documentation

Design docs, concept definitions, and references for APIs and CLIs.

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Managing Service Accounts

This is a Cluster Administrator guide to service accounts. It assumes knowledge of the User Guide to Service Accounts.

Support for authorization and user accounts is planned but incomplete. Sometimes incomplete features are referred to in order to better describe service accounts.

User accounts vs service accounts

Kubernetes distinguished between the concept of a user account and a service accounts for a number of reasons:

Service account automation

Three separate components cooperate to implement the automation around service accounts:

Service Account Admission Controller

The modification of pods is implemented via a plugin called an Admission Controller. It is part of the apiserver. It acts synchronously to modify pods as they are created or updated. When this plugin is active (and it is by default on most distributions), then it does the following when a pod is created or modified:

  1. If the pod does not have a ServiceAccount set, it sets the ServiceAccount to default.
  2. It ensures that the ServiceAccount referenced by the pod exists, and otherwise rejects it.
  3. If the pod does not contain any ImagePullSecrets, then ImagePullSecrets of the ServiceAccount are added to the pod.
  4. It adds a volume to the pod which contains a token for API access.
  5. It adds a volumeSource to each container of the pod mounted at /var/run/secrets/

Token Controller

TokenController runs as part of controller-manager. It acts asynchronously. It:

To create additional API tokens

A controller loop ensures a secret with an API token exists for each service account. To create additional API tokens for a service account, create a secret of type ServiceAccountToken with an annotation referencing the service account, and the controller will update it with a generated token:

    "kind": "Secret",
    "apiVersion": "v1",
    "metadata": {
        "name": "mysecretname",
        "annotations": {
            "": "myserviceaccount"
    "type": ""
kubectl create -f ./secret.json
kubectl describe secret mysecretname

To delete/invalidate a service account token

kubectl delete secret mysecretname

Service Account Controller

Service Account Controller manages ServiceAccount inside namespaces, and ensures a ServiceAccount named “default” exists in every active namespace.


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