What are Kubernetes Secrets?

The concept of Kubernetes Secrets refers to any type of confidential credential that requires privileged access in order to interact with it. These objects often act as keys or methods of authentication with protected computing resources in secure applications, tools, or computing environments. In this article, we’re going to discuss how Kubernetes handles Secrets and what makes a Kubernetes Secret unique.

Why are Kubernetes Secrets Important?

In a distributed computing environment, it is important that containerized applications remain ephemeral and not share their resources with other pods. This is especially true in relation to Public Key Infrastructure (PKI) authentication keys and other confidential resources that pods need to access external resources. For this reason, applications need a way to authenticate without keys and other secrets being held in the application itself.

Kubernetes offers a solution to this that follows the path of least privilege. Essentially, Kubernetes Secrets are placeholders for sensitive information like credentials, tokens, and certificates, a mechanism for abstracting them. Kubernetes Secrets act as separate objects which can be queried by the application Pod to provide credentials to the application for access to external resources. Kubernetes Secrets can only be accessed by Pods if they are explicitly part of a mounted volume or at the time when the Kubelet is pulling the image to be used for the Pod.

How Does Kubernetes Leverage Secrets?

The Kubernetes API provides various built-in Secret types for a variety of use cases found in the wild. When you create a Secret, you can declare its type by leveraging the `type` field of the Secret resource, or an equivalent `kubectl` command line flag. The Secret type is used for programmatic interaction with the Secret data.

What are the different ways to create K8s Secrets?

Kubernetes offers several methods for creating Secrets depending on your workflow and automation needs:

Using kubectl create secret

Create a Secret directly from literal values or files:

kubectl create secret generic mysecret \

  --from-literal=username=admin \

  --from-literal=password=1f2d1e2e67df

1. From files using kubectl create secret

   Useful for injecting credentials or certificates stored as files:

   kubectl create secret generic db-creds \
     --from-file=username.txt \
     --from-file=password.txt

2. From a config file

   Define a Secret in YAML or JSON using the data or stringData field and apply it with:

   kubectl apply -f mysecret.yaml

3. Using Kustomize

   Generate Secrets from files via a secretGenerator in a kustomization.yaml :

   secretGenerator:
     - name: db-user-pass
       files:
         - username.txt
         - password.txt

   Then apply with:

   kubectl apply -k .

4. Creating a TLS Secret For HTTPS or Ingress use cases:

   kubectl create secret tls my-tls-secret \
     --cert=path/to/tls.crt \
     --key=path/to/tls.key

These methods support a wide range of use cases—from local development to production GitOps pipelines—while aligning with best practices for Kubernetes Secret management.

How is a Kubernetes Secret created using kubectl?

Kubernetes provides a range of tools and techniques for managing Secrets effectively at scale. Whether you're securing service credentials or API tokens, how you manage these objects will influence the security and stability of your workloads. Managing Secrets includes creating, viewing, updating, and rotating them over time.

Secrets can be managed manually using kubectl, declaratively with configuration files, or through GitOps-style workflows using tools like Kustomize. You can also integrate external secret management systems for centralized control and compliance.

Using tools like kubectl get secret, you can retrieve individual Secret objects, while commands like kubectl list secrets let you see all available Secrets in a given namespace. These tools help platform engineers and DevOps teams audit, troubleshoot, and validate that Secrets are configured as expected.

To create a Secret via kubectl, you’re going to want to first create a text file to store the contents of your Secret, in this case a username.txt and password.txt:

echo -n 'admin' > ./username.txt
echo -n '1f2d1e2e67df' > ./password.txt

Then you’ll want to leverage the kubectl create secret to package these files into a Secret, with the final command looking like this:

kubectl create secret generic db-user-pass \
  --from-file=./username.txt \
  --from-file=./password.txt

The output should look like this:

secret/db-user-pass created

How is a Kubernetes Secret created from a config file?

You can create a Kubernetes Secret from a YAML or JSON config file by defining the apiVersion, kind, metadata, and data or stringData fields. The data field must contain base64-encoded values, while stringData accepts plain text and is easier for human editing.

You can also store your secure data in a JSON or YAML file and create a Secret object from that. The Secret resource contains two distinct maps:

• data: used to store arbitrary data, encoded using base64

• stringData: allows you to provide Secret data as unencoded strings

The keys of data and stringData must consist of alphanumeric characters, ‘-’ (dash), ‘_’ (underscore), or ‘.’ (period).

For example, to store two strings in a Secret using the data field, you can convert the strings to base64 as follows:

echo -n 'admin' | base64

The output should look like this:

YWRtaW4=

And for the next one:

echo -n '1f2d1e2e67df' | base64

The output should look similar to:

MWYyZDFlMmU2N2Rm

You can then write a secret config that looks like this:

apiVersion: v1
kind: Secret
metadata:
  name: mysecret
type: Opaque
data:
  username: YWRtaW4=
  password: MWYyZDFlMmU2N2Rm

How is a Kubernetes Secret created using kustomize?

You can also generate a Secret object by defining a secretGenerator in a kustomization.yaml file that references other existing files. For example, the following kustomization file references the ./username.txt and the ./password.txt files, for example:

secretGenerator:
- name: db-user-pass
  files:
  - username.txt
  - password.txt

Then apply the directory containing the kustomization.yaml to create the Secret:

kubectl apply -k .

The output should look similar to this:

secret/db-user-pass-96mffmfh4k created

How is a Kubernetes Secret edited?

You can edit an existing Secret with the following command:

kubectl edit secrets mysecret

This command opens the default configured editor and allows for updating the base64 encoded Secret values in the data field:

  # 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 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: 2016-01-22T18:41:56Z
  name: mysecret
  namespace: default
  resourceVersion: "164619"
  uid: cfee02d6-c137-11e5-8d73-42010af00002
type: Opaque

How are Kubernetes Secrets used?

Secrets can be used in a variety of ways, such as being mounted as data volumes or exposed as environment 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.

How can Kubernetes Secrets be used as environment variables in a Pod?

To use a secret in an environment variable in a Pod, you’ll want to:

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.

2. 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 secrets from environment variables:

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
      - name: SECRET_PASSWORD
        valueFrom:
          secretKeyRef:
            name: mysecret
            key: password
  restartPolicy: Never

How to manage Kubernetes secrets

Managing Kubernetes Secrets effectively involves creating, storing, updating, and securing sensitive data throughout the lifecycle of your workloads. Secrets can be created using kubectl create secret, defined declaratively in YAML files, or generated automatically using tools like Kustomize or GitOps pipelines. You can view and audit secrets with kubectl get secret or kubectl list secrets, and update them manually using kubectl edit secret or by reapplying updated configurations. Best practices for managing Secrets include encrypting them at rest, enforcing role-based access controls, rotating credentials regularly, and using external secret management systems when needed. Whether you're injecting Secrets as environment variables via secretKeyRef or mounting them into pods as volumes, Kubernetes offers flexible options to securely handle sensitive data at scale.

Viewing Kubernetes secrets

Use the following command to list all secrets in a namespace:

kubectl list secrets

To view a specific secret’s metadata (without decoding):

kubectl get secret mysecret -o yaml

To describe a secret and inspect associated metadata:

kubectl describe secret mysecret

Decoding Kubernetes secrets

Secret data is stored in base64-encoded format. To decode the values manually:

# View the secret

kubectl get secret mysecret -o jsonpath="{.data.username}" | base64 --decode

To decode multiple keys:

kubectl get secret mysecret -o json | jq -r '.data | to_entries[] | "\(.key): \(.value | @base64d)"'

Deleting Kubernetes secrets

To delete a specific Kubernetes Secret:

kubectl delete secret mysecret

To delete multiple secrets by label:

kubectl delete secret -l app=myapp

Updating and rotating secrets

To update a secret using a new literal value:

kubectl create secret generic mysecret \
  --from-literal=username=newuser \
  --from-literal=password=newpass \
  --dry-run=client -o yaml | kubectl apply -f -

Or use the built-in editor to manually rotate secret values:

kubectl edit secret mysecret

This is particularly useful when following best practices for secret rotation and maintaining consistency with your secret policy in Kubernetes.

Using secrets in pods

Mount secret values as environment variables using secretKeyRef :

yaml

env:
  - name: SECRET_USERNAME
    valueFrom:
      secretKeyRef:
        name: mysecret
        key: username
  - name: SECRET_PASSWORD
    valueFrom:
      secretKeyRef:
        name: mysecret
        key: password

Or mount them as files in a volume:

yaml

volumes:
  - name: secret-volume
    secret:
      secretName: mysecret

volumeMounts:
  - name: secret-volume
    mountPath: /etc/secret
    readOnly: true

What are external Kubernetes secrets?

External Kubernetes Secrets refer to a pattern where sensitive data such as passwords, API tokens, or certificates are managed outside the Kubernetes cluster and synced into it when needed. Rather than storing credentials directly in the cluster via native Secret objects, external Secrets leverage third-party providers like HashiCorp Vault, AWS Secrets Manager, Azure Key Vault, or Google Secret Manager to store and manage sensitive information securely.

This approach offers several benefits:

• Centralized secret management across multiple clusters and environments

• Improved compliance with organizational or regulatory policies

• Fine-grained access controls outside of standard Kubernetes RBAC

• Automatic secret rotation without manual intervention

To integrate external secrets into Kubernetes, the Kubernetes Secrets Store CSI Driver is commonly used. This enables a pod to mount a secret from an external provider as a volume without ever persisting the secret in etcd. These secrets are mounted at runtime and kept out of the cluster's permanent storage, which aligns with best practices for least-privilege access and ephemeral secrets usage.

This model also supports kubernetes secretKeyRef indirectly, where once synced, the secrets can be exposed to applications via environment variables or volumes in the same way as native Kubernetes Secrets.

For teams managing secrets at enterprise scale or across hybrid/multi-cloud environments, using external Kubernetes secrets is a critical step in achieving secure, policy-driven, and auditable secret management.

What are immutable Kubernetes Secrets, and what are the benefits?

Kubernetes provides an option to set individual Secrets as immutable, which can be implemented to enhance the security and performance of your cluster. For clusters that extensively use Secrets (at least tens of thousands of unique Secret to Pod mounts), preventing changes to their data has the following advantages:

• Protects you from accidental (or unwanted) updates that could cause application outages

• Improves performance of your cluster by significantly reducing load on kube-apiserver, by closing watches for Secrets marked as immutable

How are immutable Kubernetes Secrets created?

This feature is controlled by the ImmutableEphemeralVolumes feature gate, which is enabled by default since v1.19. You can create an immutable Secret by setting the immutable field to true. For example:

apiVersion: v1
kind: Secret
metadata:
  ...
data:
  ...
immutable: true

What are the built-in types of Kubernetes Secrets?

• Opaque Secrets – The default Secret type if omitted from a Secret configuration file.

• Service account token Secrets – Used to store a token that identifies a service account. 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.

• Docker config Secrets – Stores the credentials for accessing a Docker registry for images.

• Basic authentication Secret – Used for storing credentials needed for basic authentication. When using this Secret type, the `data` field of the Secret must contain the `username` and `password` keys.

• SSH authentication secrets – Used 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.

• TLS secrets – For storing a certificate and its associated key that are typically used for TLS . This data is primarily used with TLS termination of the Ingress resource, but may be used with other resources or directly by a 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.

• Bootstrap token Secrets – Used for tokens used during the node bootstrap process. It stores tokens used to sign well known ConfigMaps.

What are the limitations of Kubernetes Secrets?

Kubernetes Secrets are just one mechanism you should consider for your overall Kubernetes security strategy. Once a container has consumed a secret via an environment variable, the value is freely available within the container. The value is also stored without encryption in etcd. This doesn’t mean you shouldn’t use Kubernetes Secrets, but that you should understand their limitations, follow best practices, and know that you will need to combine it with other security mechanisms to adequately protect your Kubernetes deployments.

What are some best practices for maintaining and increasing the security of Kubernetes secrets?

Encrypt Secret data at rest

By default, etcd stores Kubernetes Secrets unencrypted. Enable at-rest encryption for your Secret objects, including the key-value data they contain.

Implement least-privilege access to Secrets

Follow RBAC best practices and only assign minimal rights to users and service accounts. Only allow the most privileged, system-level components to access watch or list, and only the components that require get access for Secrets to execute their normal functions should have it.

As for humans, only cluster admins should have access to etcd, and get, watch, and list access (including read-only access) to Secrets should be restricted. Third-party authorization solutions can provide more robust access control, such as restricting access to Secrets that have certain annotations.

Use annotations to enforce specific rules for Secret management

By annotating a ServiceAccount with kubernetes.io/enforce-mountable-secrets set to true, Kubernetes enforces specific rules for Pods running as this ServiceAccount, that require the ServiceAccount’s secrets field to include Secrets mounted as volumes as well as Secrets referenced in envFrom for containers. Additionally, the ServiceAccount’s imagePullSecrets field must include Secrets referenced in a Pod’s imagePullSecrets. These rules are enforced whenever a Pod is created or updated.

Strengthen etcd management policies

Any durable storage used by etcd that is no longer needed should be wiped or shredded. For deployments with multiple etc instances, protect Secret data in transit by encrypting SSL/TLS communication between the instances.

Use 3rd-party Secrets store providers

Keep confidential credentials and other sensitive data outside your cluster by using external Secrets store providers that Pods can access. These solutions leverage the Kubernetes Secrets Store CSI Driver.

Kubernetes secrets use cases

Kubernetes Secrets are a foundational part of secure application deployment and platform automation. They provide a flexible, built-in mechanism for managing sensitive data that needs to be accessed by applications, infrastructure components, and CI/CD pipelines within a Kubernetes environment.

Here are some of the most common use cases for Kubernetes Secrets:

1. Storing application credentials

   Store database usernames and passwords, API tokens, or third-party service keys as Secrets. These can be injected into containers as environment variables using secretKeyRef, or mounted as files in a volume. This pattern is widely used when integrating apps with databases or cloud services in a secure, repeatable way.

2. TLS termination for Ingress

   With kubectl create secret tls, you can store TLS private keys and certificates for use in Ingress controllers. This allows for secure HTTPS communication to your services without embedding sensitive credentials in your configurations.

   kubectl create secret tls my-tls-secret \
     --cert=./tls.crt \
     --key=./tls.key

3. Authenticating to container registries

   Use Secrets to store Docker registry credentials and access private container images securely. These Secrets can be referenced in a Pod's imagePullSecrets field and managed using kubectl or declarative YAML.

4. Dynamic secrets via external providers

   When used with external secrets management tools, Kubernetes Secrets enable dynamic credential injection into Pods without persisting data in etcd. This pattern is ideal for organizations enforcing compliance with zero trust and audit-friendly infrastructure policies.

5. Configuration across environments

   By using different Secrets for dev, staging, and production environments, teams can abstract away environment-specific data without changing application code. Updating a Secret with kubernetes update secret can trigger redeployments that automatically pick up new credentials.

6. Secure environment variable injection

   For applications that rely on environment-level configuration, Secrets allow injecting runtime values securely. This is commonly seen in microservices that need to pass secure tokens or API keys between services. These values are typically defined using the kubernetes environment variables from secret pattern in a Pod spec.

7. CI/CD and GitOps pipelines

   Secrets play a key role in build and deployment pipelines. Whether authenticating to artifact repositories or signing images, Secrets can be used securely and programmatically via kubectl create secret, kubectl get secret, or through GitOps tools like ArgoCD or Flux.

How are Kubernetes Secrets managed using Lens Desktop?

Lens Desktop makes it easy to create Kubernetes Secrets for a cluster using a dialog menu. Simply enter the parameters, and click Create.

After creating Kubernetes Secrets, you can view, filter, and search through a table of Secrets for each cluster and click on each item to view further details, edit, or delete it.

Conclusion

So now that you’ve had a brief introduction to what a Kubernetes Secret is, you’re ready to learn how to use them in practice. Download our free eBook, Kubernetes 5 Minutes at a Time, and check out Chapter 9,  “Secrets with Environment Variables and Volume Mounts,” to learn more, with practice exercises you can try to inject Kubernetes Secrets as environment variables or by using files in a volume.