Kubernetes Secrets refer to the objects that are used to store sensitive information like passwords, OAuth tokens, and also SSH keys. By using a Secret rather than putting confidential data in a Pod specification or a container image, you reduce the risk of exposing sensitive data during the application development process.
Developing and managing a modern-day application is much more complicated and involves more than just writing code. It also involves managing access. Every database needs a password, every API needs a token, and every secure connection needs a private key. In a containerised environment, hardcoding these details into your source code or Dockerfile is a massive security risk. This is the primary problem kubernetes secrets were designed to solve. They provide a more familiar and easy way to safely store sensitive configuration into your pods. It does this with complete confidentiality, without exposing them to anyone who has access to your version control system or container registry.
What Exactly are Kubernetes Secrets?
At its core, a Secret is a small object that contains a small amount of sensitive data. While they look similar to ConfigMaps, they are treated differently by the cluster. Kubernetes stores Secrets in etcd, the cluster’s “brain,” and by default, they are encoded in Base64. It is important to remember that Base64 is not encryption—it is simply a way to represent binary data as text. To truly secure kubernetes secrets, administrators usually enable “Encryption at Rest” within the cluster settings.
Why Not Just Use ConfigMaps?
But, you may now wonder why we don’t just use the simple method by choosing ConfigMaps for everything. The distinction here is all about intent and safety:
- ConfigMaps: For non-sensitive configuration (like a UI theme or a port number).
- Kubernetes Secrets: For data that could compromise your system if leaked (like a database password).
- Memory-based delivery: Secrets are often backed by temporary file systems (tmpfs) so the sensitive data is never written to the physical disk of the node.
Creating Your First Kubernetes Secrets YAML
To manage your infrastructure as code, you will likely define your secrets using a manifest file. A kubernetes secrets yaml file follows a specific structure. Here is a simple breakdown of how it looks:
The Structure of a Secret
YAML
apiVersion: v1
kind: Secret
metadata:
name: db-credentials
type: Opaque
data:
username: dXNlcm5hbWU=
password: cGFzc3dvcmQxMjM=
In this example of kubernetes secrets, the data field holds values that need to be Base64 encoded. However, if you want to supply the data in plain text and have Kubernetes perform the encoding for you when you create the secret, you can use the stringData field instead. This is a popular “pro-tip” for developers who want to skip the step of encoding when testing locally.
Types of Kubernetes Secrets
Kubernetes offers several built-in types to help the system handle your data correctly:
- Opaque: The default type for user-defined arbitrary data (passwords, keys).
- kubernetes.io/service-account-token: Used to identify a service account to the API.
- kubernetes.io/dockerconfigjson: Used for storing credentials for a Docker registry so the cluster can pull private images.
- kubernetes.io/tls: Specifically for TLS certificates and private keys.
How to Use Secrets in Your Pods
Once you have created your secret, your application needs to access it. There are two primary ways to consume kubernetes secrets within a pod:
1. As Environment Variables
This is the most common method. You map a key from the secret directly to an environment variable inside the container.
- Best for: Applications that expect configuration via environment variables.
- Risk: Environment variables can sometimes be logged or viewed via process inspection tools.
2. As Files in a Volume
You can also mount a secret as a volume. By this method each “key” in the secret becomes a filename. This also makes the “value” become the file’s content.
- Best for: Applications that need to read certificates or large configuration files from a specific path.
- Benefit: This is generally considered more secure as the data resides in a memory-backed volume (tmpfs).
The Role of a Kubernetes Secrets Store
As your organisation grows, managing hundreds of secrets inside individual YAML files becomes a nightmare. This is where a kubernetes secrets store comes into play. A “Secrets Store CSI Driver” allows Kubernetes to mount secrets stored in external enterprise-grade vaults directly into your pods as volumes.
By using a dedicated store, you gain:
- Centralised Management: One central place to rotate passwords across multiple clusters.
- Audit Logs: It enables you to see who exactly accessed a secret and when.
- Fine-grained Access: This allows you to use Cloud IAM roles to decide which pod gets which key.
Integrating a Kubernetes Secrets Manager
To maintain high-security and ensure a safe environment, relying only on native Kubernetes objects is not enough. Many teams mostly integrate a third-party kubernetes secrets manager like HashiCorp Vault, AWS Secrets Manager, or Azure Key Vault.
These managers provide features that native Secrets lack:
- Automatic Rotation: The manager can change your database password every 30 days and update the pod automatically.
- Dynamic Credentials: Creating a “one-time” password for a pod that expires as soon as the pod dies.
- Enhanced Encryption: Moving beyond Base64 to actual hardware-backed encryption (HSM).
Best Practices for Secret Management
To ensure your sensitive data remains truly secret, follow these essential DevOps principles:
- RBAC is Mandatory: Use Role-Based Access Control to restrict who can “get” or “describe” secrets. Most developers should not have permission to view production secrets.
- Don’t Commit Secrets to Git: Never check a kubernetes secrets yaml with real data into a repository. Use tools like Sealed Secrets or Mozilla SOPS to encrypt them before committing.
- Use External Providers: For production, lean on a kubernetes secrets store CSI driver to keep sensitive data out of the etcd database if possible.
- Enable Encryption at Rest: Ensure your cluster is configured to encrypt the etcd layer so that a physical theft of a server doesn’t result in a data breach.
Troubleshooting Common Issues
Sometimes, a pod might fail to start because of a secret issue. Look out for these common errors:
- SecretNotFound: The pod is looking for a secret name that hasn’t been created yet.
- Invalid Base64: If you manually encoded the data, a stray newline character can break the encoding.
- Permission Denied: The ServiceAccount associated with the pod doesn’t have the “get” permission for that specific secret.
Conclusion
Understanding kubernetes secrets and knowing how to implement it effectively is a non-negotiable skill for any developer in the modern times. By separating your sensitive credentials from your application logic, you create a more secure, modular, and professional deployment pipeline. Whether you start with a simple kubernetes secrets example or scale up to a full kubernetes secrets manager integration, the goal is always the same: keep your data safe and your applications running smoothly.
Frequently Asked Questions
- Is a kubernetes secrets yaml encrypted by default?
No, it is only Base64 encoded. To ensure that your data is secure it is important that you enable “Encryption at Rest” in your Kubernetes cluster settings. You can also prefer to use an external encryption tool.
- What is the main difference between ConfigMaps and kubernetes secrets?
ConfigMaps are simply meant for plain-text configuration. But mainly it is used for text that is not sensitive. Secrets are specifically for confidential data and are handled more carefully by the cluster, often being stored in memory.
- How do I update a pod when a kubernetes secrets value changes?
If the secret is mounted as a volume, the file is updated automatically. If it is used as an environment variable, you must restart the pod to pick up the new value.
- Can I use a kubernetes secrets manager like AWS or Azure?
Yes, by using the Secret Store CSI Driver, you can sync secrets from external cloud providers directly into your Kubernetes pods securely.
- Why should I avoid the kubernetes secrets hostpath approach for storage?
Storing secrets on a host node’s local disk is dangerous. If that node is compromised, all secrets on it are exposed. Always use the native Secret object or a memory-backed volume.
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