Containers and Kubernetes

One of the more advanced topics in DevOps is Kubernetes. I have been in a DevOps role for a while before I truly grasped the concept. In this blog, I attempt to explain the concept (hopefully it's clear!).

First, let us clarify some terminologies where a lot of engineers get confused.

Containers, Images, and Kubernetes

Containers - are lightweight deployable packages that has the minimum required dependencies, code, and configuration to run an application.

Image - is the blueprint of containers. Basically, it is a non-running container and is usually stored in a container registry like ECR (Elastic Container Registry), Artifactory, or Docker Hub.

Kubernetes - is a container orchestration "platform". It manages containers through all it's magic across clusters.

Kubectl Commands

Kubectl is a command line tool that allows interaction with a Kubernetes cluster. Before you can interact with Kubernetes in the cloud, you would need to setup a kubeconfig file in your local machine with either aws eks (for AWS) or az aks (for Azure).

For AWS

aws configure
aws eks update-kubeconfig --region <aws-region> --name <cluster-name>

• Replace with your AWS region (ex. us-east-1).
• Replace with your EKS cluster name.

For Azure

az login
az aks get-credentials --resource-group <resource-group> --name <cluster-name>

• Replace with your Azure Resource Group name.
• Replace with your AKS cluster name.

After running these commands, you should have a kubeconfig file setup. For MAC, this usually lives on the following path: ~/.KUBE/config.

Below are some of the common kubectl commands to know:

kubectl apply -f <file.yaml> -n <namespace> → Deploy a resource from a YAML manifest

kubectl logs -f <pod-name> -n <namespace> → View logs from a pod

kubectl exec -it <pod-name> -n <namespace> -- bash → Open an interactive shell in a running container

kubectl get events → Displays events such as pod scheduling, container creation, scaling actions, failures, or errors.

All the Commands

Below are some basic kubernetes resources and their corresponding kubectl commands.

• Pod – The smallest deployable unit in Kubernetes.

#List all pods
kubectl get pods -n <namespace>
#Get detailed info on a specific pod
kubectl describe pod <pod-name> -n <namespace>

• Deployment – Manages replicated pods and ensures their availability.

#List all deployments
kubectl get deployments -n <namespace>
#Detailed view of a deployment
kubectl describe deployment <deployment-name> -n <namespace>
#Save a definition to a file
kubectl get deployment <deployment-name> -n <namespace> -o yaml >> <file_name>
#Edit the deployment directly
kubectl edit deployment <deployment-name> -n <namespace>

• ReplicaSet – Ensures a specified number of pod replicas run at all times.

#View all replica sets
kubectl get replicasets 
#Get details on a specific ReplicaSet
kubectl describe replicaset <replicaset-name> 

• Service – Provides network access to a set of pods.

#View all services
kubectl get services 
#Get detailed info on a service
kubectl describe service <service-name> 

• ConfigMap – Stores configuration data in key-value pairs.

#List all ConfigMaps
kubectl get configmaps 
#View details of a ConfigMap
kubectl describe configmap <configmap-name> 

• Secret – Stores sensitive information like passwords or API keys.

#List all secrets
kubectl get secrets 
#Get details on a secret
kubectl describe secret <secret-name> 

• *PersistentVolume (PV) *– Represents storage in Kubernetes.

#View available persistent volumes
kubectl get pv 
#Get details on a specific PV
kubectl describe pv <pv-name> 

• PersistentVolumeClaim (PVC) – Requests storage from a PersistentVolume.

#View all PVCs
kubectl get pvc 
#Get details of a PVC
kubectl describe pvc <pvc-name> 

• Namespace – Provides a way to logically separate resources.

#View all namespaces
kubectl get namespaces 
#Get details on a namespace
kubectl describe namespace <namespace-name> 

• Node – Represents a worker machine in the cluster.

#View all nodes in the cluster
kubectl get nodes
#Get details on a node
kubectl describe node <node-name>

As always, concepts are easier to understand as you build a project in Kubernetes. Here is another blog I wrote previously that shows the container deployments with DevOps concepts: https://dev.to/aws-builders/build-a-container-package-for-your-react-app-with-docker-and-github-actions-4nf5.