# Configure Service Accounts for Pods

Configure Service Accounts for PodsKubernetes offers two distinct ways for clients that run within your cluster, or that otherwise have a relationship to your cluster's control plane to authenticate to the API server.A service account provides an identity for processes that run in a Pod, and maps to a ServiceAccount object. When you authenticate to the API server, you identify yourself as a particular user. Kubernetes recognises the concept of a user, however, Kubernetes itself does not have a User API.This task guide is about ServiceAccounts, which do exist in the Kubernetes API. The guide shows you some ways to configure ServiceAccounts for Pods.Before you beginYou need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:iximiuz LabsKillercodaKodeKloudPlay with KubernetesUse the default service account to access the API serverWhen Pods contact the API server, Pods authenticate as a particular ServiceAccount (for example, default). There is always at least one ServiceAccount in each namespace.Every Kubernetes namespace contains at least one ServiceAccount: the default ServiceAccount for that namespace, named default. If you do not specify a ServiceAccount when you create a Pod, Kubernetes automatically assigns the ServiceAccount named default in that namespace.You can fetch the details for a Pod you have created. For example:kubectl get pods/<podname> -o yaml In the output, you see a field spec.serviceAccountName. Kubernetes automatically sets that value if you don't specify it when you create a Pod.An application running inside a Pod can access the Kubernetes API using automatically mounted service account credentials. See accessing the Cluster to learn more.When a Pod authenticates as a ServiceAccount, its level of access depends on the authorization plugin and policy in use.The API credentials are automatically revoked when the Pod is deleted, even if finalizers are in place. In particular, the API credentials are revoked 60 seconds beyond the .metadata.deletionTimestamp set on the Pod (the deletion timestamp is typically the time that the delete request was accepted plus the Pod's termination grace period).Opt out of API credential automountingIf you don't want the kubelet to automatically mount a ServiceAccount's API credentials, you can opt out of the default behavior. You can opt out of automounting API credentials on /var/run/secrets/kubernetes.io/serviceaccount/token for a service account by setting automountServiceAccountToken: false on the ServiceAccount:For example:apiVersion: v1 kind: ServiceAccount metadata: name: build-robot automountServiceAccountToken: false ... You can also opt out of automounting API credentials for a particular Pod:apiVersion: v1 kind: Pod metadata: name: my-pod spec: serviceAccountName: build-robot automountServiceAccountToken: false ... If both the ServiceAccount and the Pod's .spec specify a value for automountServiceAccountToken, the Pod spec takes precedence.Use more than one ServiceAccountEvery namespace has at least one ServiceAccount: the default ServiceAccount resource, called default. You can list all ServiceAccount resources in your current namespace with:kubectl get serviceaccounts The output is similar to this:NAME SECRETS AGE default 1 1d You can create additional ServiceAccount objects like this:kubectl apply -f - <<EOF apiVersion: v1 kind: ServiceAccount metadata: name: build-robot EOF The name of a ServiceAccount object must be a valid DNS subdomain name.If you get a complete dump of the service account object, like this:kubectl get serviceaccounts/build-robot -o yaml The output is similar to this:apiVersion: v1 kind: ServiceAccount metadata: creationTimestamp: 2019-06-16T00:12:34Z name: build-robot namespace: default resourceVersion: "272500" uid: 721ab723-13bc-11e5-aec2-42010af0021e You can use authorization plugins to set permissions on service accounts.To use a non-default service account, set the spec.serviceAccountName field of a Pod to the name of the ServiceAccount you wish to use.You can only set the serviceAccountName field when creating a Pod, or in a template for a new Pod. You cannot update the .spec.serviceAccountName field of a Pod that already exists.Note:The .spec.serviceAccount field is a deprecated alias for .spec.serviceAccountName. If you want to remove the fields from a workload resource, set both fields to empty explicitly on the pod template.CleanupIf you tried creating build-robot ServiceAccount from the example above, you can clean it up by running:kubectl delete serviceaccount/build-robot Manually create an API token for a ServiceAccountSuppose you have an existing service account named "build-robot" as mentioned earlier.You can get a time-limited API token for that ServiceAccount using kubectl:kubectl create token build-robot The output from that command is a token that you can use to authenticate as that ServiceAccount. You can request a specific token duration using the --duration command line argument to kubectl create token (the actual duration of the issued token might be shorter, or could even be longer).FEATURE STATE: Kubernetes v1.33 [stable] (enabled by default: true)Using kubectl v1.31 or later, it is possible to create a service account token that is directly bound to a Node:kubectl create token build-robot --bound-object-kind Node --bound-object-name node-001 --bound-object-uid 123...456 The token will be valid until it expires or either the associated Node or service account are deleted.Note:Versions of Kubernetes before v1.22 automatically created long term credentials for accessing the Kubernetes API. This older mechanism was based on creating token Secrets that could then be mounted into running Pods. In more recent versions, including Kubernetes v1.34, API credentials are obtained directly by using the TokenRequest API, and are mounted into Pods using a projected volume. The tokens obtained using this method have bounded lifetimes, and are automatically invalidated when the Pod they are mounted into is deleted.You can still manually create a service account token Secret; for example, if you need a token that never expires. However, using the TokenRequest subresource to obtain a token to access the API is recommended instead.Manually create a long-lived API token for a ServiceAccountIf you want to obtain an API token for a ServiceAccount, you create a new Secret with a special annotation, kubernetes.io/service-account.name.kubectl apply -f - <<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 If you view the Secret using:kubectl get secret/build-robot-secret -o yaml you can see that the Secret now contains an API token for the "build-robot" ServiceAccount.Because of the annotation you set, the control plane automatically generates a token for that ServiceAccounts, and stores them into the associated Secret. The control plane also cleans up tokens for deleted ServiceAccounts.kubectl describe secrets/build-robot-secret The output is similar to this:Name: build-robot-secret Namespace: default Labels: <none> Annotations: kubernetes.io/service-account.name: build-robot kubernetes.io/service-account.uid: da68f9c6-9d26-11e7-b84e-002dc52800da Type: kubernetes.io/service-account-token Data ==== ca.crt: 1338 bytes namespace: 7 bytes token: ... Note:The content of token is omitted here.Take care not to display the contents of a kubernetes.io/service-account-token Secret somewhere that your terminal / computer screen could be seen by an onlooker.When you delete a ServiceAccount that has an associated Secret, the Kubernetes control plane automatically cleans up the long-lived token from that Secret.Note:If you view the ServiceAccount using:kubectl get serviceaccount build-robot -o yamlYou can't see the build-robot-secret Secret in the ServiceAccount API objects .secrets field because that field is only populated with auto-generated Secrets.Add ImagePullSecrets to a service accountFirst, create an imagePullSecret. Next, verify it has been created. For example:Create an imagePullSecret, as described in Specifying ImagePullSecrets on a Pod.kubectl create secret docker-registry myregistrykey --docker-server=<registry name> \ --docker-username=DUMMY_USERNAME --docker-password=DUMMY_DOCKER_PASSWORD \ --docker-email=DUMMY_DOCKER_EMAIL Verify it has been created.kubectl get secrets myregistrykey The output is similar to this:NAME TYPE DATA AGE myregistrykey kubernetes.io/.dockerconfigjson 1 1d Add image pull secret to service accountNext, modify the default service account for the namespace to use this Secret as an imagePullSecret.kubectl patch serviceaccount default -p '{"imagePullSecrets": [{"name": "myregistrykey"}]}' You can achieve the same outcome by editing the object manually:kubectl edit serviceaccount/default The output of the sa.yaml file is similar to this:Your selected text editor will open with a configuration looking something like this:apiVersion: v1 kind: ServiceAccount metadata: creationTimestamp: 2021-07-07T22:02:39Z name: default namespace: default resourceVersion: "243024" uid: 052fb0f4-3d50-11e5-b066-42010af0d7b6 Using your editor, delete the line with key resourceVersion, add lines for imagePullSecrets: and save it. Leave the uid value set the same as you found it.After you made those changes, the edited ServiceAccount looks something like this:apiVersion: v1 kind: ServiceAccount metadata: creationTimestamp: 2021-07-07T22:02:39Z name: default namespace: default uid: 052fb0f4-3d50-11e5-b066-42010af0d7b6 imagePullSecrets: - name: myregistrykey Verify that imagePullSecrets are set for new PodsNow, when a new Pod is created in the current namespace and using the default ServiceAccount, the new Pod has its spec.imagePullSecrets field set automatically:kubectl run nginx --image=<registry name>/nginx --restart=Never kubectl get pod nginx -o=jsonpath='{.spec.imagePullSecrets[0].name}{"\n"}' The output is:myregistrykey ServiceAccount token volume projectionFEATURE STATE: Kubernetes v1.20 [stable]Note:To enable and use token request projection, you must specify each of the following command line arguments to kube-apiserver:--service-account-issuerdefines the Identifier of the service account token issuer. You can specify the --service-account-issuer argument multiple times, this can be useful to enable a non-disruptive change of the issuer. When this flag is specified multiple times, the first is used to generate tokens and all are used to determine which issuers are accepted. You must be running Kubernetes v1.22 or later to be able to specify --service-account-issuer multiple times.--service-account-key-filespecifies the path to a file containing PEM-encoded X.509 private or public keys (RSA or ECDSA), used to verify ServiceAccount tokens. The specified file can contain multiple keys, and the flag can be specified multiple times with different files. If specified multiple times, tokens signed by any of the specified keys are considered valid by the Kubernetes API server.--service-account-signing-key-filespecifies the path to a file that contains the current private key of the service account token issuer. The issuer signs issued ID tokens with this private key.--api-audiences (can be omitted)defines audiences for ServiceAccount tokens. The service account token authenticator validates that tokens used against the API are bound to at least one of these audiences. If api-audiences is specified multiple times, tokens for any of the specified audiences are considered valid by the Kubernetes API server. If you specify the --service-account-issuer command line argument but you don't set --api-audiences, the control plane defaults to a single element audience list that contains only the issuer URL.The kubelet can also project a ServiceAccount token into a Pod. You can specify desired properties of the token, such as the audience and the validity duration. These properties are not configurable on the default ServiceAccount token. The token will also become invalid against the API when either the Pod or the ServiceAccount is deleted.You can configure this behavior for the spec of a Pod using a projected volume type called ServiceAccountToken.The token from this projected volume is a JSON Web Token (JWT). The JSON payload of this token follows a well defined schema - an example payload for a pod bound token:{ "aud": [ # matches the requested audiences, or the API server's default audiences when none are explicitly requested "https://kubernetes.default.svc" ], "exp": 1731613413, "iat": 1700077413, "iss": "https://kubernetes.default.svc", # matches the first value passed to the --service-account-issuer flag "jti": "ea28ed49-2e11-4280-9ec5-bc3d1d84661a", "kubernetes.io": { "namespace": "kube-system", "node": { "name": "127.0.0.1", "uid": "58456cb0-dd00-45ed-b797-5578fdceaced" }, "pod": { "name": "coredns-69cbfb9798-jv9gn", "uid": "778a530c-b3f4-47c0-9cd5-ab018fb64f33" }, "serviceaccount": { "name": "coredns", "uid": "a087d5a0-e1dd-43ec-93ac-f13d89cd13af" }, "warnafter": 1700081020 }, "nbf": 1700077413, "sub": "system:serviceaccount:kube-system:coredns" } Launch a Pod using service account token projectionTo provide a Pod with a token with an audience of vault and a validity duration of two hours, you could define a Pod manifest that is similar to:pods/pod-projected-svc-token.yaml apiVersion: v1 kind: Pod metadata: name: nginx spec: containers: - image: nginx name: nginx volumeMounts: - mountPath: /var/run/secrets/tokens name: vault-token serviceAccountName: build-robot volumes: - name: vault-token projected: sources: - serviceAccountToken: path: vault-token expirationSeconds: 7200 audience: vault Create the Pod:kubectl create -f https://k8s.io/examples/pods/pod-projected-svc-token.yaml The kubelet will: request and store the token on behalf of the Pod; make the token available to the Pod at a configurable file path; and refresh the token as it approaches expiration. The kubelet proactively requests rotation for the token if it is older than 80% of its total time-to-live (TTL), or if the token is older than 24 hours.The application is responsible for reloading the token when it rotates. It's often good enough for the application to load the token on a schedule (for example: once every 5 minutes), without tracking the actual expiry time.Service account issuer discoveryFEATURE STATE: Kubernetes v1.21 [stable]If you have enabled token projection for ServiceAccounts in your cluster, then you can also make use of the discovery feature. Kubernetes provides a way for clients to federate as an identity provider, so that one or more external systems can act as a relying party.Note:The issuer URL must comply with the OIDC Discovery Spec. In practice, this means it must use the https scheme, and should serve an OpenID provider configuration at {service-account-issuer}/.well-known/openid-configuration.If the URL does not comply, ServiceAccount issuer discovery endpoints are not registered or accessible.When enabled, the Kubernetes API server publishes an OpenID Provider Configuration document via HTTP. The configuration document is published at /.well-known/openid-configuration. The OpenID Provider Configuration is sometimes referred to as the discovery document. The Kubernetes API server publishes the related JSON Web Key Set (JWKS), also via HTTP, at /openid/v1/jwks.Note:The responses served at /.well-known/openid-configuration and /openid/v1/jwks are designed to be OIDC compatible, but not strictly OIDC compliant. Those documents contain only the parameters necessary to perform validation of Kubernetes service account tokens.Clusters that use RBAC include a default ClusterRole called system:service-account-issuer-discovery. A default ClusterRoleBinding assigns this role to the system:serviceaccounts group, which all ServiceAccounts implicitly belong to. This allows pods running on the cluster to access the service account discovery document via their mounted service account token. Administrators may, additionally, choose to bind the role to system:authenticated or system:unauthenticated depending on their security requirements and which external systems they intend to federate with.The JWKS response contains public keys that a relying party can use to validate the Kubernetes service account tokens. Relying parties first query for the OpenID Provider Configuration, and use the jwks_uri field in the response to find the JWKS.In many cases, Kubernetes API servers are not available on the public internet, but public endpoints that serve cached responses from the API server can be made available by users or by service providers. In these cases, it is possible to override the jwks_uri in the OpenID Provider Configuration so that it points to the public endpoint, rather than the API server's address, by passing the --service-account-jwks-uri flag to the API server. Like the issuer URL, the JWKS URI is required to use the https scheme.What's nextSee also:Read the Cluster Admin Guide to Service AccountsRead about Authorization in KubernetesRead about Secretsor learn to distribute credentials securely using Secretsbut also bear in mind that using Secrets for authenticating as a ServiceAccount is deprecated. The recommended alternative is ServiceAccount token volume projection.Read about projected volumes.For background on OIDC discovery, read the ServiceAccount signing key retrieval Kubernetes Enhancement ProposalRead the OIDC Discovery Spec