Introduction
In the world of cloud-native applications, interacting with clusters through command-line interfaces (CLI) and APIs is fundamental for administrators and developers alike. Kubernetes and Red Hat OpenShift both provide powerful command-line tools and REST APIs that allow users to manage, monitor, and troubleshoot their clusters efficiently. This blog will explore how you can access an OpenShift cluster via CLI and query its Kubernetes API to assess cluster health and resource status.
🔧 CLI Tools: The Gateway to Your Cluster
- kubectl – The Kubernetes Command Line Tool kubectl is the standard CLI used to interact with Kubernetes clusters. With it, users can:
Deploy and manage applications
Inspect resources
View logs and events
Control cluster behavior
Example Tasks:
View pods: kubectl get pods
Check node status: kubectl get nodes
Get deployment info: kubectl describe deployment
- oc – The OpenShift CLI The oc tool is built on top of kubectl, adding OpenShift-specific features for enhanced cluster interaction. It offers all the functionality of kubectl plus:
Managing OpenShift projects
Interacting with Source-to-Image (S2I) builds
Handling OpenShift routes, templates, and operators
Useful Commands:
oc get projects – List all OpenShift projects
oc new-app – Quickly deploy applications
oc whoami – View logged-in user details
🌐 Accessing and Querying the Kubernetes API
OpenShift is built on Kubernetes and exposes the Kubernetes API, allowing you to programmatically interact with the cluster.
Why Access the Kubernetes API?
Automate monitoring or reporting tools
Integrate custom dashboards or tools
Perform health checks or dynamic configuration
API Access Steps:
Authentication – You must authenticate using a service account token or user credentials.
API Exploration – Use tools like curl or Postman to make API requests: nginxCopyEditcurl -k -H "Authorization: Bearer " https:///api
Health Checks – Access endpoints like /healthz, /metrics, or /apis to get cluster health insights.
🩺 Assessing Cluster Health via CLI and API
Using both CLI tools and APIs, you can:
Monitor the status of nodes and pods
Check resource usage (CPU, memory)
Query event logs to detect failures or warnings
Validate API server responsiveness
Audit cluster components (schedulers, controllers, etc.)
Key CLI Health Commands:
kubectl get componentstatuses
oc get events --sort-by='.lastTimestamp'
kubectl top pods (requires Metrics Server)
🛡️ Benefits of Using CLI & API
Efficiency: Perform bulk or repetitive tasks quickly
Automation: Easily integrate with scripts or CI/CD pipelines
Insight: Gain full visibility into application and system behavior
Flexibility: Access resources even when GUI is unavailable
Conclusion
Mastering Kubernetes and OpenShift’s command-line interfaces and APIs unlocks powerful ways to manage your cluster environments. Whether you're deploying applications, checking system health, or automating tasks, these tools give you the flexibility and control needed to operate effectively in any containerized ecosystem.
By learning how to access and query your cluster using the CLI and APIs, you're well on your way to becoming a more effective cloud-native practitioner.
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