A service account provides an identity for processes that run in a Pod.
This is a user introduction to Service Accounts. See also the Cluster Admin Guide to Service Accounts.
Note: This document describes how service accounts behave in a cluster set up as recommended by the Kubernetes project. Your cluster administrator may have customized the behavior in your cluster, in which case this documentation may not apply.
When you (a human) access the cluster (e.g. using kubectl), you are
authenticated by the apiserver as a particular User Account (currently this is
usually admin, unless your cluster administrator has customized your
cluster). Processes in containers inside pods can also contact the apiserver.
When they do, they are authenticated as a particular Service Account (e.g.
default).
Using the Default Service Account to access the API server.
When you create a pod, you do not need to specify a service account. It is
automatically assigned the default service account of the same namespace. If
you get the raw json or yaml for a pod you have created (e.g. kubectl get
pods/podname -o yaml), you can see the spec.serviceAccount field has been
automatically set.
With service accounts, you can access the API inside the pod using a proxy or with a client library, as described in Accessing the Cluster.
Using Multiple Service Accounts.
Every namespace has a default service account resource called default.
You can list this and any other serviceAccount resources in the namespace with this command:
$ kubectl get serviceAccounts
NAME SECRETS
default 1
You can create additional serviceAccounts like this:
$ cat > /tmp/serviceaccount.yaml <<EOF
apiVersion: v1
kind: ServiceAccount
metadata:
name: build-robot
EOF
$ kubectl create -f /tmp/serviceaccount.yaml
serviceaccounts/build-robot
If you get a complete dump of the service account object, like this:
$ kubectl get serviceaccounts/build-robot -o yaml
apiVersion: v1
kind: ServiceAccount
metadata:
creationTimestamp: 2015-06-16T00:12:59Z
name: build-robot
namespace: default
resourceVersion: "272500"
selfLink: /api/v1/namespaces/default/serviceaccounts/build-robot
uid: 721ab723-13bc-11e5-aec2-42010af0021e
secrets:
- name: build-robot-token-bvbk5
then you will see that a token has automatically been created and is referenced by the service account.
You may use the ABAC authorization plugin to set permissions on service accounts.
To use a non-default service account, simply set the spec.serviceAccount
field of a pod to the name of the service account you wish to use.
The service account has to exist at the time the pod is created, or it will be rejected.
You cannot update the service account of an already created pod.
You can clean up the service account from this example like this:
$ kubectl delete serviceaccount/build-robot
Note that if a pod does not have a ServiceAccount set, the ServiceAccount will be set to default.
Manually create a service account API token.
Suppose we have an existing service account named “build-robot” as mentioned above, and we create a new secret manually.
$ cat > /tmp/build-robot-secret.yaml <<EOF
apiVersion: v1
kind: Secret
metadata:
name: build-robot-secret
annotations:
kubernetes.io/service-account.name: build-robot
type: kubernetes.io/service-account-token
EOF
$ kubectl create -f /tmp/build-robot-secret.yaml
secrets/build-robot-secret
Now you can confirm that the newly built secret is populated with an API token for the “build-robot” service account.
Any tokens for non-existent service accounts will be cleaned up by the token controller.
$ kubectl describe secrets/build-robot-secret
Name: build-robot-secret
Namespace: default
Labels: <none>
Annotations: kubernetes.io/service-account.name=build-robot,kubernetes.io/service-account.uid=870ef2a5-35cf-11e5-8d06-005056b45392
Type: kubernetes.io/service-account-token
Data
====
ca.crt: 1220 bytes
token: ...
namespace: 7 bytes
Note that the content of
tokenis elided here.
Adding ImagePullSecrets to a service account
First, create an imagePullSecret, as described here Next, verify it has been created. For example:
$ kubectl get secrets myregistrykey
NAME TYPE DATA
myregistrykey kubernetes.io/.dockerconfigjson 1
Next, read/modify/write the service account for the namespace to use this secret as an imagePullSecret
$ kubectl get serviceaccounts default -o yaml > ./sa.yaml
$ cat sa.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
creationTimestamp: 2015-08-07T22:02:39Z
name: default
namespace: default
resourceVersion: "243024"
selfLink: /api/v1/namespaces/default/serviceaccounts/default
uid: 052fb0f4-3d50-11e5-b066-42010af0d7b6
secrets:
- name: default-token-uudge
$ vi sa.yaml
[editor session not shown]
[delete line with key "resourceVersion"]
[add lines with "imagePullSecret:"]
$ cat sa.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
creationTimestamp: 2015-08-07T22:02:39Z
name: default
namespace: default
selfLink: /api/v1/namespaces/default/serviceaccounts/default
uid: 052fb0f4-3d50-11e5-b066-42010af0d7b6
secrets:
- name: default-token-uudge
imagePullSecrets:
- name: myregistrykey
$ kubectl replace serviceaccount default -f ./sa.yaml
serviceaccounts/default
Now, any new pods created in the current namespace will have this added to their spec:
spec:
imagePullSecrets:
- name: myregistrykey
Adding Secrets to a service account.
TODO: Test and explain how to use additional non-K8s secrets with an existing service account.
TODO explain: - The token goes to: “/var/run/secrets/kubernetes.io/serviceaccount/$WHATFILENAME”