In our journey through Kubernetes RBAC, we’ve covered Roles, RoleBindings, ClusterRoles, and ClusterRoleBindings. Today, we’re diving into another crucial component of Kubernetes security: Service Accounts.
What are Service Accounts?
In Kubernetes, there are two types of accounts:
- User Accounts: Used by humans (admins, developers, operators)
- Service Accounts: Used by processes running in pods to interact with the Kubernetes API
Service Accounts are crucial for applications running within your cluster that need to interact with the Kubernetes API or other services.
Creating and Managing Service Accounts
Let’s start with the basics:
Creating a Service Account
kubectl create serviceaccount my-app-sa
Viewing Service Accounts
kubectl get serviceaccounts# orkubectl get sa
Hands-on: Using Service Accounts with RBAC
Let’s walk through a practical example of creating and using a Service Account with RBAC.
Step 1: Create a Service Account
kubectl create serviceaccount pod-reader-sa
Step 2: Create a Role
apiVersion: rbac.authorization.k8s.io/v1kind: Rolemetadata: namespace: default name: pod-readerrules: - apiGroups: [""] resources: ["pods"] verbs: ["get", "watch", "list"]
Save this as pod-reader-role.yaml
and apply:
kubectl apply -f pod-reader-role.yaml
Step 3: Create a RoleBinding
apiVersion: rbac.authorization.k8s.io/v1kind: RoleBindingmetadata: name: read-pods namespace: defaultsubjects: - kind: ServiceAccount name: pod-reader-sa namespace: defaultroleRef: kind: Role name: pod-reader apiGroup: rbac.authorization.k8s.io
Save this as pod-reader-rolebinding.yaml
and apply:
kubectl apply -f pod-reader-rolebinding.yaml
Step 4: Use the Service Account in a Pod
Now, let’s create a pod that uses this Service Account:
apiVersion: v1kind: Podmetadata: name: pod-reader-podspec: serviceAccountName: pod-reader-sa containers: - name: my-container image: busybox command: ["sh", "-c", "while true; do kubectl get pods; sleep 10; done"]
Save this as pod-reader-pod.yaml
and apply:
kubectl apply -f pod-reader-pod.yaml
This pod will use the pod-reader-sa
Service Account, which has permissions to list pods in the default namespace.
Key Takeaways
- Automation-Friendly: Service Accounts are ideal for automated processes and applications running in your cluster.
- Namespace Scoped: Unlike ClusterRoles, Service Accounts are namespace-specific.
- Default Service Account: Each namespace has a default Service Account, but it’s best practice to create specific ones for your applications.
- Token Authentication: Service Accounts use tokens for authentication, which are automatically mounted into pods.
- RBAC Integration: Service Accounts can be bound to Roles or ClusterRoles just like user accounts.
Best Practices
- Least Privilege: Always grant the minimum necessary permissions to your Service Accounts.
- Unique Accounts: Create separate Service Accounts for different applications or components.
- Regular Audits: Periodically review your Service Accounts and their permissions.
- Avoid Using Default: Don’t rely on the default Service Account; create specific ones for your needs.
- Rotate Tokens: Regularly rotate Service Account tokens for enhanced security.
Conclusion
Service Accounts are a fundamental part of Kubernetes security and RBAC. They allow you to grant specific permissions to processes running within your cluster, enabling secure interactions between your applications and the Kubernetes API. By understanding and properly implementing Service Accounts, you can significantly enhance the security posture of your Kubernetes deployments.
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