--- reviewers: - mikedanese title: Secrets content_type: concept feature: title: Secret and configuration management description: > Deploy and update secrets and application configuration without rebuilding your image and without exposing secrets in your stack configuration. weight: 30 --- A Secret is an object that contains a small amount of sensitive data such as a password, a token, or a key. Such information might otherwise be put in a {{< glossary_tooltip term_id="pod" >}} specification or in a {{< glossary_tooltip text="container image" term_id="image" >}}. Using a Secret means that you don't need to include confidential data in your application code. Because Secrets can be created independently of the Pods that use them, there is less risk of the Secret (and its data) being exposed during the workflow of creating, viewing, and editing Pods. Kubernetes, and applications that run in your cluster, can also take additional precautions with Secrets, such as avoiding writing secret data to nonvolatile storage. Secrets are similar to {{< glossary_tooltip text="ConfigMaps" term_id="configmap" >}} but are specifically intended to hold confidential data. {{< caution >}} Kubernetes Secrets are, by default, stored unencrypted in the API server's underlying data store (etcd). Anyone with API access can retrieve or modify a Secret, and so can anyone with access to etcd. Additionally, anyone who is authorized to create a Pod in a namespace can use that access to read any Secret in that namespace; this includes indirect access such as the ability to create a Deployment. In order to safely use Secrets, take at least the following steps: 1. [Enable Encryption at Rest](/docs/tasks/administer-cluster/encrypt-data/) for Secrets. 1. [Enable or configure RBAC rules](/docs/reference/access-authn-authz/authorization/) with least-privilege access to Secrets. 1. Restrict Secret access to specific containers. 1. [Consider using external Secret store providers](https://secrets-store-csi-driver.sigs.k8s.io/concepts.html#provider-for-the-secrets-store-csi-driver). For more guidelines to manage and improve the security of your Secrets, refer to [Good practices for Kubernetes Secrets](/docs/concepts/security/secrets-good-practices). {{< /caution >}} See [Information security for Secrets](#information-security-for-secrets) for more details. ## Uses for Secrets There are three main ways for a Pod to use a Secret: - As [files](#using-secrets-as-files-from-a-pod) in a {{< glossary_tooltip text="volume" term_id="volume" >}} mounted on one or more of its containers. - As [container environment variable](#using-secrets-as-environment-variables). - By the [kubelet when pulling images](#using-imagepullsecrets) for the Pod. The Kubernetes control plane also uses Secrets; for example, [bootstrap token Secrets](#bootstrap-token-secrets) are a mechanism to help automate node registration. ### Alternatives to Secrets Rather than using a Secret to protect confidential data, you can pick from alternatives. Here are some of your options: - if your cloud-native component needs to authenticate to another application that you know is running within the same Kubernetes cluster, you can use a [ServiceAccount](/docs/reference/access-authn-authz/authentication/#service-account-tokens) and its tokens to identify your client. - there are third-party tools that you can run, either within or outside your cluster, that provide secrets management. For example, a service that Pods access over HTTPS, that reveals a secret if the client correctly authenticates (for example, with a ServiceAccount token). - for authentication, you can implement a custom signer for X.509 certificates, and use [CertificateSigningRequests](/docs/reference/access-authn-authz/certificate-signing-requests/) to let that custom signer issue certificates to Pods that need them. - you can use a [device plugin](/docs/concepts/extend-kubernetes/compute-storage-net/device-plugins/) to expose node-local encryption hardware to a specific Pod. For example, you can schedule trusted Pods onto nodes that provide a Trusted Platform Module, configured out-of-band. You can also combine two or more of those options, including the option to use Secret objects themselves. For example: implement (or deploy) an {{< glossary_tooltip text="operator" term_id="operator-pattern" >}} that fetches short-lived session tokens from an external service, and then creates Secrets based on those short-lived session tokens. Pods running in your cluster can make use of the session tokens, and operator ensures they are valid. This separation means that you can run Pods that are unaware of the exact mechanisms for issuing and refreshing those session tokens. ## Working with Secrets ### Creating a Secret There are several options to create a Secret: - [create Secret using `kubectl` command](/docs/tasks/configmap-secret/managing-secret-using-kubectl/) - [create Secret from config file](/docs/tasks/configmap-secret/managing-secret-using-config-file/) - [create Secret using kustomize](/docs/tasks/configmap-secret/managing-secret-using-kustomize/) #### Constraints on Secret names and data {#restriction-names-data} The name of a Secret object must be a valid [DNS subdomain name](/docs/concepts/overview/working-with-objects/names#dns-subdomain-names). You can specify the `data` and/or the `stringData` field when creating a configuration file for a Secret. The `data` and the `stringData` fields are optional. The values for all keys in the `data` field have to be base64-encoded strings. If the conversion to base64 string is not desirable, you can choose to specify the `stringData` field instead, which accepts arbitrary strings as values. The keys of `data` and `stringData` must consist of alphanumeric characters, `-`, `_` or `.`. All key-value pairs in the `stringData` field are internally merged into the `data` field. If a key appears in both the `data` and the `stringData` field, the value specified in the `stringData` field takes precedence. #### Size limit {#restriction-data-size} Individual secrets are limited to 1MiB in size. This is to discourage creation of very large secrets that could exhaust the API server and kubelet memory. However, creation of many smaller secrets could also exhaust memory. You can use a [resource quota](/docs/concepts/policy/resource-quotas/) to limit the number of Secrets (or other resources) in a namespace. ### Editing a Secret You can edit an existing Secret using kubectl: ```shell kubectl edit secrets mysecret ``` This opens your default editor and allows you to update the base64 encoded Secret values in the `data` field; for example: ```yaml # Please edit the object below. Lines beginning with a '#' will be ignored, # and an empty file will abort the edit. If an error occurs while saving this file, it will be # reopened with the relevant failures. # apiVersion: v1 data: username: YWRtaW4= password: MWYyZDFlMmU2N2Rm kind: Secret metadata: annotations: kubectl.kubernetes.io/last-applied-configuration: { ... } creationTimestamp: 2020-01-22T18:41:56Z name: mysecret namespace: default resourceVersion: "164619" uid: cfee02d6-c137-11e5-8d73-42010af00002 type: Opaque ``` That example manifest defines a Secret with two keys in the `data` field: `username` and `password`. The values are Base64 strings in the manifest; however, when you use the Secret with a Pod then the kubelet provides the _decoded_ data to the Pod and its containers. You can package many keys and values into one Secret, or use many Secrets, whichever is convenient. ### Using a Secret Secrets can be mounted as data volumes or exposed as {{< glossary_tooltip text="environment variables" term_id="container-env-variables" >}} to be used by a container in a Pod. Secrets can also be used by other parts of the system, without being directly exposed to the Pod. For example, Secrets can hold credentials that other parts of the system should use to interact with external systems on your behalf. Secret volume sources are validated to ensure that the specified object reference actually points to an object of type Secret. Therefore, a Secret needs to be created before any Pods that depend on it. If the Secret cannot be fetched (perhaps because it does not exist, or due to a temporary lack of connection to the API server) the kubelet periodically retries running that Pod. The kubelet also reports an Event for that Pod, including details of the problem fetching the Secret. #### Optional Secrets {#restriction-secret-must-exist} When you define a container environment variable based on a Secret, you can mark it as _optional_. The default is for the Secret to be required. None of a Pod's containers will start until all non-optional Secrets are available. If a Pod references a specific key in a Secret and that Secret does exist, but is missing the named key, the Pod fails during startup. ### Using Secrets as files from a Pod {#using-secrets-as-files-from-a-pod} If you want to access data from a Secret in a Pod, one way to do that is to have Kubernetes make the value of that Secret be available as a file inside the filesystem of one or more of the Pod's containers. To configure that, you: 1. Create a secret or use an existing one. Multiple Pods can reference the same secret. 1. Modify your Pod definition to add a volume under `.spec.volumes[]`. Name the volume anything, and have a `.spec.volumes[].secret.secretName` field equal to the name of the Secret object. 1. Add a `.spec.containers[].volumeMounts[]` to each container that needs the secret. Specify `.spec.containers[].volumeMounts[].readOnly = true` and `.spec.containers[].volumeMounts[].mountPath` to an unused directory name where you would like the secrets to appear. 1. Modify your image or command line so that the program looks for files in that directory. Each key in the secret `data` map becomes the filename under `mountPath`. This is an example of a Pod that mounts a Secret named `mysecret` in a volume: ```yaml apiVersion: v1 kind: Pod metadata: name: mypod spec: containers: - name: mypod image: redis volumeMounts: - name: foo mountPath: "/etc/foo" readOnly: true volumes: - name: foo secret: secretName: mysecret optional: false # default setting; "mysecret" must exist ``` Each Secret you want to use needs to be referred to in `.spec.volumes`. If there are multiple containers in the Pod, then each container needs its own `volumeMounts` block, but only one `.spec.volumes` is needed per Secret. {{< note >}} Versions of Kubernetes before v1.22 automatically created 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 v{{< skew currentVersion >}}, API credentials are obtained directly by using the [TokenRequest](/docs/reference/kubernetes-api/authentication-resources/token-request-v1/) API, and are mounted into Pods using a [projected volume](/docs/reference/access-authn-authz/service-accounts-admin/#bound-service-account-token-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](/docs/tasks/configure-pod-container/configure-service-account/#manually-create-a-service-account-api-token) a service account token Secret; for example, if you need a token that never expires. However, using the [TokenRequest](/docs/reference/kubernetes-api/authentication-resources/token-request-v1/) subresource to obtain a token to access the API is recommended instead. You can use the [`kubectl create token`](/docs/reference/generated/kubectl/kubectl-commands#-em-token-em-) command to obtain a token from the `TokenRequest` API. {{< /note >}} #### Projection of Secret keys to specific paths You can also control the paths within the volume where Secret keys are projected. You can use the `.spec.volumes[].secret.items` field to change the target path of each key: ```yaml apiVersion: v1 kind: Pod metadata: name: mypod spec: containers: - name: mypod image: redis volumeMounts: - name: foo mountPath: "/etc/foo" readOnly: true volumes: - name: foo secret: secretName: mysecret items: - key: username path: my-group/my-username ``` What will happen: * the `username` key from `mysecret` is available to the container at the path `/etc/foo/my-group/my-username` instead of at `/etc/foo/username`. * the `password` key from that Secret object is not projected. If `.spec.volumes[].secret.items` is used, only keys specified in `items` are projected. To consume all keys from the Secret, all of them must be listed in the `items` field. If you list keys explicitly, then all listed keys must exist in the corresponding Secret. Otherwise, the volume is not created. #### Secret files permissions You can set the POSIX file access permission bits for a single Secret key. If you don't specify any permissions, `0644` is used by default. You can also set a default mode for the entire Secret volume and override per key if needed. For example, you can specify a default mode like this: ```yaml apiVersion: v1 kind: Pod metadata: name: mypod spec: containers: - name: mypod image: redis volumeMounts: - name: foo mountPath: "/etc/foo" volumes: - name: foo secret: secretName: mysecret defaultMode: 0400 ``` The secret is mounted on `/etc/foo`; all the files created by the secret volume mount have permission `0400`. {{< note >}} If you're defining a Pod or a Pod template using JSON, beware that the JSON specification doesn't support octal notation. You can use the decimal value for the `defaultMode` (for example, 0400 in octal is 256 in decimal) instead. If you're writing YAML, you can write the `defaultMode` in octal. {{< /note >}} #### Consuming Secret values from volumes Inside the container that mounts a secret volume, the secret keys appear as files. The secret values are base64 decoded and stored inside these files. This is the result of commands executed inside the container from the example above: ```shell ls /etc/foo/ ``` The output is similar to: ``` username password ``` ```shell cat /etc/foo/username ``` The output is similar to: ``` admin ``` ```shell cat /etc/foo/password ``` The output is similar to: ``` 1f2d1e2e67df ``` The program in a container is responsible for reading the secret data from these files, as needed. #### Mounted Secrets are updated automatically When a volume contains data from a Secret, and that Secret is updated, Kubernetes tracks this and updates the data in the volume, using an eventually-consistent approach. {{< note >}} A container using a Secret as a [subPath](/docs/concepts/storage/volumes#using-subpath) volume mount does not receive automated Secret updates. {{< /note >}} The kubelet keeps a cache of the current keys and values for the Secrets that are used in volumes for pods on that node. You can configure the way that the kubelet detects changes from the cached values. The `configMapAndSecretChangeDetectionStrategy` field in the [kubelet configuration](/docs/reference/config-api/kubelet-config.v1beta1/) controls which strategy the kubelet uses. The default strategy is `Watch`. Updates to Secrets can be either propagated by an API watch mechanism (the default), based on a cache with a defined time-to-live, or polled from the cluster API server on each kubelet synchronisation loop. As a result, the total delay from the moment when the Secret is updated to the moment when new keys are projected to the Pod can be as long as the kubelet sync period + cache propagation delay, where the cache propagation delay depends on the chosen cache type (following the same order listed in the previous paragraph, these are: watch propagation delay, the configured cache TTL, or zero for direct polling). ### Using Secrets as environment variables To use a Secret in an {{< glossary_tooltip text="environment variable" term_id="container-env-variables" >}} in a Pod: 1. Create a Secret (or use an existing one). Multiple Pods can reference the same Secret. 1. Modify your Pod definition in each container that you wish to consume the value of a secret key to add an environment variable for each secret key you wish to consume. The environment variable that consumes the secret key should populate the secret's name and key in `env[].valueFrom.secretKeyRef`. 1. Modify your image and/or command line so that the program looks for values in the specified environment variables. This is an example of a Pod that uses a Secret via environment variables: ```yaml apiVersion: v1 kind: Pod metadata: name: secret-env-pod spec: containers: - name: mycontainer image: redis env: - name: SECRET_USERNAME valueFrom: secretKeyRef: name: mysecret key: username optional: false # same as default; "mysecret" must exist # and include a key named "username" - name: SECRET_PASSWORD valueFrom: secretKeyRef: name: mysecret key: password optional: false # same as default; "mysecret" must exist # and include a key named "password" restartPolicy: Never ``` #### Invalid environment variables {#restriction-env-from-invalid} Secrets used to populate environment variables by the `envFrom` field that have keys that are considered invalid environment variable names will have those keys skipped. The Pod is allowed to start. If you define a Pod with an invalid variable name, the failed Pod startup includes an event with the reason set to `InvalidVariableNames` and a message that lists the skipped invalid keys. The following example shows a Pod that refers to a Secret named `mysecret`, where `mysecret` contains 2 invalid keys: `1badkey` and `2alsobad`. ```shell kubectl get events ``` The output is similar to: ``` LASTSEEN FIRSTSEEN COUNT NAME KIND SUBOBJECT TYPE REASON 0s 0s 1 dapi-test-pod Pod Warning InvalidEnvironmentVariableNames kubelet, 127.0.0.1 Keys [1badkey, 2alsobad] from the EnvFrom secret default/mysecret were skipped since they are considered invalid environment variable names. ``` #### Consuming Secret values from environment variables Inside a container that consumes a Secret using environment variables, the secret keys appear as normal environment variables. The values of those variables are the base64 decoded values of the secret data. This is the result of commands executed inside the container from the example above: ```shell echo "$SECRET_USERNAME" ``` The output is similar to: ``` admin ``` ```shell echo "$SECRET_PASSWORD" ``` The output is similar to: ``` 1f2d1e2e67df ``` {{< note >}} If a container already consumes a Secret in an environment variable, a Secret update will not be seen by the container unless it is restarted. There are third party solutions for triggering restarts when secrets change. {{< /note >}} ### Container image pull secrets {#using-imagepullsecrets} If you want to fetch container images from a private repository, you need a way for the kubelet on each node to authenticate to that repository. You can configure _image pull secrets_ to make this possible. These secrets are configured at the Pod level. The `imagePullSecrets` field for a Pod is a list of references to Secrets in the same namespace as the Pod. You can use an `imagePullSecrets` to pass image registry access credentials to the kubelet. The kubelet uses this information to pull a private image on behalf of your Pod. See `PodSpec` in the [Pod API reference](/docs/reference/kubernetes-api/workload-resources/pod-v1/#PodSpec) for more information about the `imagePullSecrets` field. #### Using imagePullSecrets The `imagePullSecrets` field is a list of references to secrets in the same namespace. You can use an `imagePullSecrets` to pass a secret that contains a Docker (or other) image registry password to the kubelet. The kubelet uses this information to pull a private image on behalf of your Pod. See the [PodSpec API](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#podspec-v1-core) for more information about the `imagePullSecrets` field. ##### Manually specifying an imagePullSecret You can learn how to specify `imagePullSecrets` from the [container images](/docs/concepts/containers/images/#specifying-imagepullsecrets-on-a-pod) documentation. ##### Arranging for imagePullSecrets to be automatically attached You can manually create `imagePullSecrets`, and reference these from a ServiceAccount. Any Pods created with that ServiceAccount or created with that ServiceAccount by default, will get their `imagePullSecrets` field set to that of the service account. See [Add ImagePullSecrets to a service account](/docs/tasks/configure-pod-container/configure-service-account/#add-imagepullsecrets-to-a-service-account) for a detailed explanation of that process. ### Using Secrets with static Pods {#restriction-static-pod} You cannot use ConfigMaps or Secrets with {{< glossary_tooltip text="static Pods" term_id="static-pod" >}}. ## Use cases ### Use case: As container environment variables Create a secret ```yaml apiVersion: v1 kind: Secret metadata: name: mysecret type: Opaque data: USER_NAME: YWRtaW4= PASSWORD: MWYyZDFlMmU2N2Rm ``` Create the Secret: ```shell kubectl apply -f mysecret.yaml ``` Use `envFrom` to define all of the Secret's data as container environment variables. The key from the Secret becomes the environment variable name in the Pod. ```yaml apiVersion: v1 kind: Pod metadata: name: secret-test-pod spec: containers: - name: test-container image: registry.k8s.io/busybox command: [ "/bin/sh", "-c", "env" ] envFrom: - secretRef: name: mysecret restartPolicy: Never ``` ### Use case: Pod with SSH keys Create a Secret containing some SSH keys: ```shell kubectl create secret generic ssh-key-secret --from-file=ssh-privatekey=/path/to/.ssh/id_rsa --from-file=ssh-publickey=/path/to/.ssh/id_rsa.pub ``` The output is similar to: ``` secret "ssh-key-secret" created ``` You can also create a `kustomization.yaml` with a `secretGenerator` field containing ssh keys. {{< caution >}} Think carefully before sending your own SSH keys: other users of the cluster may have access to the Secret. You could instead create an SSH private key representing a service identity that you want to be accessible to all the users with whom you share the Kubernetes cluster, and that you can revoke if the credentials are compromised. {{< /caution >}} Now you can create a Pod which references the secret with the SSH key and consumes it in a volume: ```yaml apiVersion: v1 kind: Pod metadata: name: secret-test-pod labels: name: secret-test spec: volumes: - name: secret-volume secret: secretName: ssh-key-secret containers: - name: ssh-test-container image: mySshImage volumeMounts: - name: secret-volume readOnly: true mountPath: "/etc/secret-volume" ``` When the container's command runs, the pieces of the key will be available in: ``` /etc/secret-volume/ssh-publickey /etc/secret-volume/ssh-privatekey ``` The container is then free to use the secret data to establish an SSH connection. ### Use case: Pods with prod / test credentials This example illustrates a Pod which consumes a secret containing production credentials and another Pod which consumes a secret with test environment credentials. You can create a `kustomization.yaml` with a `secretGenerator` field or run `kubectl create secret`. ```shell kubectl create secret generic prod-db-secret --from-literal=username=produser --from-literal=password=Y4nys7f11 ``` The output is similar to: ``` secret "prod-db-secret" created ``` You can also create a secret for test environment credentials. ```shell kubectl create secret generic test-db-secret --from-literal=username=testuser --from-literal=password=iluvtests ``` The output is similar to: ``` secret "test-db-secret" created ``` {{< note >}} Special characters such as `$`, `\`, `*`, `=`, and `!` will be interpreted by your [shell](https://en.wikipedia.org/wiki/Shell_(computing)) and require escaping. In most shells, the easiest way to escape the password is to surround it with single quotes (`'`). For example, if your actual password is `S!B\*d$zDsb=`, you should execute the command this way: ```shell kubectl create secret generic dev-db-secret --from-literal=username=devuser --from-literal=password='S!B\*d$zDsb=' ``` You do not need to escape special characters in passwords from files (`--from-file`). {{< /note >}} Now make the Pods: ```shell cat < pod.yaml apiVersion: v1 kind: List items: - kind: Pod apiVersion: v1 metadata: name: prod-db-client-pod labels: name: prod-db-client spec: volumes: - name: secret-volume secret: secretName: prod-db-secret containers: - name: db-client-container image: myClientImage volumeMounts: - name: secret-volume readOnly: true mountPath: "/etc/secret-volume" - kind: Pod apiVersion: v1 metadata: name: test-db-client-pod labels: name: test-db-client spec: volumes: - name: secret-volume secret: secretName: test-db-secret containers: - name: db-client-container image: myClientImage volumeMounts: - name: secret-volume readOnly: true mountPath: "/etc/secret-volume" EOF ``` Add the pods to the same `kustomization.yaml`: ```shell cat <> kustomization.yaml resources: - pod.yaml EOF ``` Apply all those objects on the API server by running: ```shell kubectl apply -k . ``` Both containers will have the following files present on their filesystems with the values for each container's environment: ``` /etc/secret-volume/username /etc/secret-volume/password ``` Note how the specs for the two Pods differ only in one field; this facilitates creating Pods with different capabilities from a common Pod template. You could further simplify the base Pod specification by using two service accounts: 1. `prod-user` with the `prod-db-secret` 1. `test-user` with the `test-db-secret` The Pod specification is shortened to: ```yaml apiVersion: v1 kind: Pod metadata: name: prod-db-client-pod labels: name: prod-db-client spec: serviceAccount: prod-db-client containers: - name: db-client-container image: myClientImage ``` ### Use case: dotfiles in a secret volume You can make your data "hidden" by defining a key that begins with a dot. This key represents a dotfile or "hidden" file. For example, when the following secret is mounted into a volume, `secret-volume`: ```yaml apiVersion: v1 kind: Secret metadata: name: dotfile-secret data: .secret-file: dmFsdWUtMg0KDQo= --- apiVersion: v1 kind: Pod metadata: name: secret-dotfiles-pod spec: volumes: - name: secret-volume secret: secretName: dotfile-secret containers: - name: dotfile-test-container image: registry.k8s.io/busybox command: - ls - "-l" - "/etc/secret-volume" volumeMounts: - name: secret-volume readOnly: true mountPath: "/etc/secret-volume" ``` The volume will contain a single file, called `.secret-file`, and the `dotfile-test-container` will have this file present at the path `/etc/secret-volume/.secret-file`. {{< note >}} Files beginning with dot characters are hidden from the output of `ls -l`; you must use `ls -la` to see them when listing directory contents. {{< /note >}} ### Use case: Secret visible to one container in a Pod Consider a program that needs to handle HTTP requests, do some complex business logic, and then sign some messages with an HMAC. Because it has complex application logic, there might be an unnoticed remote file reading exploit in the server, which could expose the private key to an attacker. This could be divided into two processes in two containers: a frontend container which handles user interaction and business logic, but which cannot see the private key; and a signer container that can see the private key, and responds to simple signing requests from the frontend (for example, over localhost networking). With this partitioned approach, an attacker now has to trick the application server into doing something rather arbitrary, which may be harder than getting it to read a file. ## Types of Secret {#secret-types} When creating a Secret, you can specify its type using the `type` field of the [Secret](/docs/reference/kubernetes-api/config-and-storage-resources/secret-v1/) resource, or certain equivalent `kubectl` command line flags (if available). The Secret type is used to facilitate programmatic handling of the Secret data. Kubernetes provides several built-in types for some common usage scenarios. These types vary in terms of the validations performed and the constraints Kubernetes imposes on them. | Built-in Type | Usage | |--------------|-------| | `Opaque` | arbitrary user-defined data | | `kubernetes.io/service-account-token` | ServiceAccount token | | `kubernetes.io/dockercfg` | serialized `~/.dockercfg` file | | `kubernetes.io/dockerconfigjson` | serialized `~/.docker/config.json` file | | `kubernetes.io/basic-auth` | credentials for basic authentication | | `kubernetes.io/ssh-auth` | credentials for SSH authentication | | `kubernetes.io/tls` | data for a TLS client or server | | `bootstrap.kubernetes.io/token` | bootstrap token data | You can define and use your own Secret type by assigning a non-empty string as the `type` value for a Secret object (an empty string is treated as an `Opaque` type). Kubernetes doesn't impose any constraints on the type name. However, if you are using one of the built-in types, you must meet all the requirements defined for that type. If you are defining a type of secret that's for public use, follow the convention and structure the secret type to have your domain name before the name, separated by a `/`. For example: `cloud-hosting.example.net/cloud-api-credentials`. ### Opaque secrets `Opaque` is the default Secret type if omitted from a Secret configuration file. When you create a Secret using `kubectl`, you will use the `generic` subcommand to indicate an `Opaque` Secret type. For example, the following command creates an empty Secret of type `Opaque`. ```shell kubectl create secret generic empty-secret kubectl get secret empty-secret ``` The output looks like: ``` NAME TYPE DATA AGE empty-secret Opaque 0 2m6s ``` The `DATA` column shows the number of data items stored in the Secret. In this case, `0` means you have created an empty Secret. ### Service account token Secrets A `kubernetes.io/service-account-token` type of Secret is used to store a token credential that identifies a {{< glossary_tooltip text="service account" term_id="service-account" >}}. Since 1.22, this type of Secret is no longer used to mount credentials into Pods, and obtaining tokens via the [TokenRequest](/docs/reference/kubernetes-api/authentication-resources/token-request-v1/) API is recommended instead of using service account token Secret objects. Tokens obtained from the `TokenRequest` API are more secure than ones stored in Secret objects, because they have a bounded lifetime and are not readable by other API clients. You can use the [`kubectl create token`](/docs/reference/generated/kubectl/kubectl-commands#-em-token-em-) command to obtain a token from the `TokenRequest` API. You should only create a service account token Secret object if you can't use the `TokenRequest` API to obtain a token, and the security exposure of persisting a non-expiring token credential in a readable API object is acceptable to you. When using this Secret type, you need to ensure that the `kubernetes.io/service-account.name` annotation is set to an existing service account name. If you are creating both the ServiceAccount and the Secret objects, you should create the ServiceAccount object first. After the Secret is created, a Kubernetes {{< glossary_tooltip text="controller" term_id="controller" >}} fills in some other fields such as the `kubernetes.io/service-account.uid` annotation, and the `token` key in the `data` field, which is populated with an authentication token. The following example configuration declares a service account token Secret: ```yaml apiVersion: v1 kind: Secret metadata: name: secret-sa-sample annotations: kubernetes.io/service-account.name: "sa-name" type: kubernetes.io/service-account-token data: # You can include additional key value pairs as you do with Opaque Secrets extra: YmFyCg== ``` After creating the Secret, wait for Kubernetes to populate the `token` key in the `data` field. See the [ServiceAccount](/docs/tasks/configure-pod-container/configure-service-account/) documentation for more information on how service accounts work. You can also check the `automountServiceAccountToken` field and the `serviceAccountName` field of the [`Pod`](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#pod-v1-core) for information on referencing service account credentials from within Pods. ### Docker config Secrets You can use one of the following `type` values to create a Secret to store the credentials for accessing a container image registry: - `kubernetes.io/dockercfg` - `kubernetes.io/dockerconfigjson` The `kubernetes.io/dockercfg` type is reserved to store a serialized `~/.dockercfg` which is the legacy format for configuring Docker command line. When using this Secret type, you have to ensure the Secret `data` field contains a `.dockercfg` key whose value is content of a `~/.dockercfg` file encoded in the base64 format. The `kubernetes.io/dockerconfigjson` type is designed for storing a serialized JSON that follows the same format rules as the `~/.docker/config.json` file which is a new format for `~/.dockercfg`. When using this Secret type, the `data` field of the Secret object must contain a `.dockerconfigjson` key, in which the content for the `~/.docker/config.json` file is provided as a base64 encoded string. Below is an example for a `kubernetes.io/dockercfg` type of Secret: ```yaml apiVersion: v1 kind: Secret metadata: name: secret-dockercfg type: kubernetes.io/dockercfg data: .dockercfg: | "" ``` {{< note >}} If you do not want to perform the base64 encoding, you can choose to use the `stringData` field instead. {{< /note >}} When you create these types of Secrets using a manifest, the API server checks whether the expected key exists in the `data` field, and it verifies if the value provided can be parsed as a valid JSON. The API server doesn't validate if the JSON actually is a Docker config file. When you do not have a Docker config file, or you want to use `kubectl` to create a Secret for accessing a container registry, you can do: ```shell kubectl create secret docker-registry secret-tiger-docker \ --docker-email=tiger@acme.example \ --docker-username=tiger \ --docker-password=pass1234 \ --docker-server=my-registry.example:5000 ``` That command creates a Secret of type `kubernetes.io/dockerconfigjson`. If you dump the `.data.dockerconfigjson` field from that new Secret and then decode it from base64: ```shell kubectl get secret secret-tiger-docker -o jsonpath='{.data.*}' | base64 -d ``` then the output is equivalent to this JSON document (which is also a valid Docker configuration file): ```json { "auths": { "my-registry.example:5000": { "username": "tiger", "password": "pass1234", "email": "tiger@acme.example", "auth": "dGlnZXI6cGFzczEyMzQ=" } } } ``` {{< note >}} The `auth` value there is base64 encoded; it is obscured but not secret. Anyone who can read that Secret can learn the registry access bearer token. {{< /note >}} ### Basic authentication Secret The `kubernetes.io/basic-auth` type is provided for storing credentials needed for basic authentication. When using this Secret type, the `data` field of the Secret must contain one of the following two keys: - `username`: the user name for authentication - `password`: the password or token for authentication Both values for the above two keys are base64 encoded strings. You can, of course, provide the clear text content using the `stringData` for Secret creation. The following manifest is an example of a basic authentication Secret: ```yaml apiVersion: v1 kind: Secret metadata: name: secret-basic-auth type: kubernetes.io/basic-auth stringData: username: admin # required field for kubernetes.io/basic-auth password: t0p-Secret # required field for kubernetes.io/basic-auth ``` The basic authentication Secret type is provided only for convenience. You can create an `Opaque` type for credentials used for basic authentication. However, using the defined and public Secret type (`kubernetes.io/basic-auth`) helps other people to understand the purpose of your Secret, and sets a convention for what key names to expect. The Kubernetes API verifies that the required keys are set for a Secret of this type. ### SSH authentication secrets The builtin type `kubernetes.io/ssh-auth` is provided for storing data used in SSH authentication. When using this Secret type, you will have to specify a `ssh-privatekey` key-value pair in the `data` (or `stringData`) field as the SSH credential to use. The following manifest is an example of a Secret used for SSH public/private key authentication: ```yaml apiVersion: v1 kind: Secret metadata: name: secret-ssh-auth type: kubernetes.io/ssh-auth data: # the data is abbreviated in this example ssh-privatekey: | MIIEpQIBAAKCAQEAulqb/Y ... ``` The SSH authentication Secret type is provided only for user's convenience. You could instead create an `Opaque` type Secret for credentials used for SSH authentication. However, using the defined and public Secret type (`kubernetes.io/ssh-auth`) helps other people to understand the purpose of your Secret, and sets a convention for what key names to expect. and the API server does verify if the required keys are provided in a Secret configuration. {{< caution >}} SSH private keys do not establish trusted communication between an SSH client and host server on their own. A secondary means of establishing trust is needed to mitigate "man in the middle" attacks, such as a `known_hosts` file added to a ConfigMap. {{< /caution >}} ### TLS secrets Kubernetes provides a builtin Secret type `kubernetes.io/tls` for storing a certificate and its associated key that are typically used for TLS. One common use for TLS secrets is to configure encryption in transit for an [Ingress](/docs/concepts/services-networking/ingress/), but you can also use it with other resources or directly in your workload. When using this type of Secret, the `tls.key` and the `tls.crt` key must be provided in the `data` (or `stringData`) field of the Secret configuration, although the API server doesn't actually validate the values for each key. The following YAML contains an example config for a TLS Secret: ```yaml apiVersion: v1 kind: Secret metadata: name: secret-tls type: kubernetes.io/tls data: # the data is abbreviated in this example tls.crt: | MIIC2DCCAcCgAwIBAgIBATANBgkqh ... tls.key: | MIIEpgIBAAKCAQEA7yn3bRHQ5FHMQ ... ``` The TLS Secret type is provided for user's convenience. You can create an `Opaque` for credentials used for TLS server and/or client. However, using the builtin Secret type helps ensure the consistency of Secret format in your project; the API server does verify if the required keys are provided in a Secret configuration. When creating a TLS Secret using `kubectl`, you can use the `tls` subcommand as shown in the following example: ```shell kubectl create secret tls my-tls-secret \ --cert=path/to/cert/file \ --key=path/to/key/file ``` The public/private key pair must exist before hand. The public key certificate for `--cert` must be DER format as per [Section 5.1 of RFC 7468](https://datatracker.ietf.org/doc/html/rfc7468#section-5.1), and must match the given private key for `--key` (PKCS #8 in DER format; [Section 11 of RFC 7468](https://datatracker.ietf.org/doc/html/rfc7468#section-11)). {{< note >}} A kubernetes.io/tls Secret stores the Base64-encoded DER data for keys and certificates. If you're familiar with PEM format for private keys and for certificates, the base64 data are the same as that format except that you omit the initial and the last lines that are used in PEM. For example, for a certificate, you do **not** include `--------BEGIN CERTIFICATE-----` and `-------END CERTIFICATE----`. {{< /note >}} ### Bootstrap token Secrets A bootstrap token Secret can be created by explicitly specifying the Secret `type` to `bootstrap.kubernetes.io/token`. This type of Secret is designed for tokens used during the node bootstrap process. It stores tokens used to sign well-known ConfigMaps. A bootstrap token Secret is usually created in the `kube-system` namespace and named in the form `bootstrap-token-` where `` is a 6 character string of the token ID. As a Kubernetes manifest, a bootstrap token Secret might look like the following: ```yaml apiVersion: v1 kind: Secret metadata: name: bootstrap-token-5emitj namespace: kube-system type: bootstrap.kubernetes.io/token data: auth-extra-groups: c3lzdGVtOmJvb3RzdHJhcHBlcnM6a3ViZWFkbTpkZWZhdWx0LW5vZGUtdG9rZW4= expiration: MjAyMC0wOS0xM1QwNDozOToxMFo= token-id: NWVtaXRq token-secret: a3E0Z2lodnN6emduMXAwcg== usage-bootstrap-authentication: dHJ1ZQ== usage-bootstrap-signing: dHJ1ZQ== ``` A bootstrap type Secret has the following keys specified under `data`: - `token-id`: A random 6 character string as the token identifier. Required. - `token-secret`: A random 16 character string as the actual token secret. Required. - `description`: A human-readable string that describes what the token is used for. Optional. - `expiration`: An absolute UTC time using RFC3339 specifying when the token should be expired. Optional. - `usage-bootstrap-`: A boolean flag indicating additional usage for the bootstrap token. - `auth-extra-groups`: A comma-separated list of group names that will be authenticated as in addition to the `system:bootstrappers` group. The above YAML may look confusing because the values are all in base64 encoded strings. In fact, you can create an identical Secret using the following YAML: ```yaml apiVersion: v1 kind: Secret metadata: # Note how the Secret is named name: bootstrap-token-5emitj # A bootstrap token Secret usually resides in the kube-system namespace namespace: kube-system type: bootstrap.kubernetes.io/token stringData: auth-extra-groups: "system:bootstrappers:kubeadm:default-node-token" expiration: "2020-09-13T04:39:10Z" # This token ID is used in the name token-id: "5emitj" token-secret: "kq4gihvszzgn1p0r" # This token can be used for authentication usage-bootstrap-authentication: "true" # and it can be used for signing usage-bootstrap-signing: "true" ``` ## Immutable Secrets {#secret-immutable} {{< feature-state for_k8s_version="v1.21" state="stable" >}} Kubernetes lets you mark specific Secrets (and ConfigMaps) as _immutable_. Preventing changes to the data of an existing Secret has the following benefits: - protects you from accidental (or unwanted) updates that could cause applications outages - (for clusters that extensively use Secrets - at least tens of thousands of unique Secret to Pod mounts), switching to immutable Secrets improves the performance of your cluster by significantly reducing load on kube-apiserver. The kubelet does not need to maintain a [watch] on any Secrets that are marked as immutable. ### Marking a Secret as immutable {#secret-immutable-create} You can create an immutable Secret by setting the `immutable` field to `true`. For example, ```yaml apiVersion: v1 kind: Secret metadata: ... data: ... immutable: true ``` You can also update any existing mutable Secret to make it immutable. {{< note >}} Once a Secret or ConfigMap is marked as immutable, it is _not_ possible to revert this change nor to mutate the contents of the `data` field. You can only delete and recreate the Secret. Existing Pods maintain a mount point to the deleted Secret - it is recommended to recreate these pods. {{< /note >}} ## Information security for Secrets Although ConfigMap and Secret work similarly, Kubernetes applies some additional protection for Secret objects. Secrets often hold values that span a spectrum of importance, many of which can cause escalations within Kubernetes (e.g. service account tokens) and to external systems. Even if an individual app can reason about the power of the Secrets it expects to interact with, other apps within the same namespace can render those assumptions invalid. A Secret is only sent to a node if a Pod on that node requires it. For mounting secrets into Pods, the kubelet stores a copy of the data into a `tmpfs` so that the confidential data is not written to durable storage. Once the Pod that depends on the Secret is deleted, the kubelet deletes its local copy of the confidential data from the Secret. There may be several containers in a Pod. By default, containers you define only have access to the default ServiceAccount and its related Secret. You must explicitly define environment variables or map a volume into a container in order to provide access to any other Secret. There may be Secrets for several Pods on the same node. However, only the Secrets that a Pod requests are potentially visible within its containers. Therefore, one Pod does not have access to the Secrets of another Pod. {{< warning >}} Any containers that run with `privileged: true` on a node can access all Secrets used on that node. {{< /warning >}} ## {{% heading "whatsnext" %}} - For guidelines to manage and improve the security of your Secrets, refer to [Good practices for Kubernetes Secrets](/docs/concepts/security/secrets-good-practices). - Learn how to [manage Secrets using `kubectl`](/docs/tasks/configmap-secret/managing-secret-using-kubectl/) - Learn how to [manage Secrets using config file](/docs/tasks/configmap-secret/managing-secret-using-config-file/) - Learn how to [manage Secrets using kustomize](/docs/tasks/configmap-secret/managing-secret-using-kustomize/) - Read the [API reference](/docs/reference/kubernetes-api/config-and-storage-resources/secret-v1/) for `Secret`