Managing Nodes and Pods in Kubernetes: Essential Commands You Should Know

 Kubernetes provides several powerful commands for managing nodes and pods effectively. Beyond cordoning and uncordoning, there are many other important operations that help maintain a healthy and efficient cluster. This post explores additional Kubernetes commands you can use to manage your cluster’s resources seamlessly.

Draining a Node

Draining is used to safely evict all workloads from a node, often as part of maintenance or scaling operations.

Command to drain a node:

kubectl drain <node-name> --ignore-daemonsets --delete-emptydir-data

This command evicts all pods except those managed by daemonsets or pods with emptyDir volumes if the flag --delete-emptydir-data is used.

Example:

kubectl drain worker-node1 --ignore-daemonsets --delete-emptydir-data

To ensure pods are rescheduled on other nodes, ensure your cluster has sufficient capacity before draining.

Tainting and Untainting Nodes

Taints allow you to control which pods can be scheduled on specific nodes.

Command to add a taint:

kubectl taint nodes <node-name> <key>=<value>:<effect>

Example:

kubectl taint nodes worker-node1 environment=production:NoSchedule

This prevents any pods without a matching toleration from being scheduled on worker-node1.

To remove a taint:

kubectl taint nodes <node-name> <key>-

Example:

kubectl taint nodes worker-node1 environment-

Labeling Nodes

Labels allow you to categorize nodes and apply scheduling rules based on these categories.

Command to add a label:

kubectl label nodes <node-name> <key>=<value>

Example:

kubectl label nodes worker-node1 zone=us-west-1

Command to remove a label:

kubectl label nodes <node-name> <key>-

Example:

kubectl label nodes worker-node1 zone-

Evicting Pods

In scenarios where you need to remove specific pods manually, you can use the eviction command.

Command to evict a pod:

kubectl delete pod <pod-name> --grace-period=<seconds>

Example:

kubectl delete pod nginx-deployment-12345 --grace-period=30

The --grace-period flag ensures the pod is terminated gracefully, giving it time to clean up resources.

Scaling Deployments

Scaling allows you to adjust the number of replicas for a deployment.

Command to scale a deployment:

kubectl scale deployment <deployment-name> --replicas=<number>

Example:

kubectl scale deployment nginx-deployment --replicas=5

Scaling ensures that Kubernetes adjusts the number of pods for the deployment accordingly.

Viewing Node and Pod Resources

It’s essential to monitor resource usage on nodes and pods to prevent bottlenecks or overloading.

Command to describe a node:

kubectl describe node <node-name>

Example:

kubectl describe node worker-node1

Command to describe a pod:

kubectl describe pod <pod-name>

Example:

kubectl describe pod nginx-deployment-12345

These commands provide detailed insights into resource allocations and usage.

Checking Pod Logs

Pod logs are crucial for debugging application issues.

Command to view logs:

kubectl logs <pod-name>

Example:

kubectl logs nginx-deployment-12345

To view logs from a specific container in a multi-container pod:

kubectl logs <pod-name> -c <container-name>

Example:

kubectl logs nginx-deployment-12345 -c nginx-container

Deleting a Node

If you need to remove a node from the cluster, use the delete command.

Command to delete a node:

kubectl delete node <node-name>

Example:

kubectl delete node worker-node1

This command permanently removes the node from the cluster.

Managing Configurations

Using configmaps or secrets to manage configurations is a common practice in Kubernetes.

Command to create a configmap:

kubectl create configmap <configmap-name> --from-literal=<key>=<value>

Example:

kubectl create configmap app-config --from-literal=log_level=debug

Command to create a secret:

kubectl create secret generic <secret-name> --from-literal=<key>=<value>

Example:

kubectl create secret generic db-secret --from-literal=username=admin --from-literal=password=securepass

Configmaps and secrets can be mounted to pods as environment variables or volumes for secure access.

Managing a Kubernetes cluster effectively requires mastery over key commands for nodes, pods, and configurations. By using commands like drain, taint, and scale, you can ensure your cluster remains healthy and optimized. Are there other Kubernetes commands you frequently use? Share your thoughts and experiences in the comments!