kubernetesssssssssssssssssssssssssss.pdf
- 1. Kubernetes Easy Understanding Concepts of Kubernetes: Notes: 1. Kubernetes Basics: ● Pods: Smallest deployable units in Kubernetes that can hold one or multiple containers. ● Nodes: Worker machines in Kubernetes. ● Clusters: A set of worker machines, called nodes, that run containerized applications. ● Kubectl: Command-line tool for interacting with a Kubernetes cluster. ● Kubelet: An agent running on each node in the cluster. ● API Server: Front-end to the cluster's control plane. ● Etcd: Consistent and highly-available key-value store used as Kubernetes' backing store for all cluster data. ● Control Plane: The collection of processes that control Kubernetes nodes. ● Namespace: Virtual clusters backed by the same physical cluster. 2. Workloads & Controllers: ● Deployments: Manages a replicated application. ● ReplicaSets: Ensures that a specified number of replicas of a Pod are running at all times. ● StatefulSets: Manages the deployment and scaling of a set of Pods, providing guarantees about ordering and uniqueness. ● DaemonSets: Ensures that all (or some) nodes run a copy of a Pod. ● Jobs: Creates one or more Pods and ensures that a specified number of them successfully terminate. ● CronJobs: Manages time-based Jobs, such as running a Job at a specific time or periodic intervals. ● Horizontal Pod Autoscaler: Automatically scales the number of Pods in a deployment, replica set, or replication controller based on observed CPU or memory usage.
- 2. 3. Services & Networking: ● Services: A way to expose an application running in Pods as a network service. ● Ingress: Manages external access to services within a cluster. ● Network Policies: Define how Pods communicate with each other. ● Service Discovery: Mechanism to connect to services dynamically based on a logical name. ● Load Balancer: A service that distributes network traffic across multiple Pods. 4. Configuration & Secrets: ● ConfigMaps: Manage configuration data separately from container images. ● Secrets: Manages sensitive information, such as passwords, OAuth tokens, and ssh keys. ● Environment Variables: Used within Kubernetes for service discovery. ● Volumes: Persistent storage in Kubernetes. ● Persistent Volume Claims (PVCs): Request for storage by a user. 5. Monitoring, Logging, and Debugging: ● Kube-state-metrics: A simple service that listens to the Kubernetes API server and generates metrics about the state of the objects. ● Prometheus: An open-source system monitoring and alerting toolkit. ● Grafana: Open platform for beautiful analytics and monitoring (often used with Prometheus). ● ELK Stack: Elasticsearch, Logstash, and Kibana used for logging in Kubernetes. ● Kubernetes Dashboard: General-purpose web UI for Kubernetes clusters. ● Kubectl Debug: Tool for debugging pods. ● Heapster: Collects monitoring and performance metrics.
- 3. 6. Security & Authorization: ● Role-Based Access Control (RBAC): Access control system. ● Security Policies: Security constraints applied to a Pod. ● Service Account: Identity attached to Pods to interact with the Kubernetes API Server. ● Transport Layer Security (TLS): Protocol for privacy and data integrity. 7. Kubernetes Storage: ● Persistent Volumes (PVs): Offers storage to the cluster that is independent of Pod life cycles. ● Storage Classes: Allow administrators to describe the "classes" of storage offered. 8. Kubernetes Cluster Maintenance: ● Node Maintenance: Taking a node down for service or replacing a failing node. ● Cluster Upgrades: Upgrading the cluster to a newer version. ● Backup and Disaster Recovery: Ensuring data continuity and integrity. 9. Extending Kubernetes: ● Custom Resources: Extension of the Kubernetes API. ● API Server Extension: Custom endpoints in the Kubernetes API. ● Custom Controllers: Automate handling of Custom Resources. ● Operators: Application-specific controllers to create, configure, and manage instances of complex stateful applications. 10. Advanced Features: ● Service Mesh (e.g., Istio): Manage microservices in a transparent way. ● Pod Priority & Preemption: Specifies priorities for Pods and allows preemption of lower-priority Pods. ● Taints and Tolerations: Allows a node to repel a set of Pods.
- 4. ● Node Affinity: Controls where a Pod runs based on labels on nodes and conditions called node affinity rules. ● Pod Presets: Injects information like secrets, volume mounts, and environment variables into pods at creation time. 11. Kubernetes Cloud Integration: ● Amazon EKS: Managed Kubernetes service on AWS. ● Google Kubernetes Engine (GKE): Managed Kubernetes service on Google Cloud. ● Azure AKS: Managed Kubernetes service on Azure. 12. Continuous Deployment/Integration in Kubernetes: ● Jenkins: Popular open-source tool to perform continuous integration and build automation. ● GitLab CI: Continuous integration service included with GitLab that builds and tests the software whenever a developer pushes code to the application. 13. Helm: Kubernetes Package Manager: ● Helm Charts: Packages of pre-configured Kubernetes resources. ● Helm Repository: A collection of charts for Kubernetes packages. 14. Kubernetes Custom Scheduling: ● Custom Scheduler: You can implement a custom scheduler to have more control over the scheduling of your Pods. 15. Kubernetes Federation: ● Cluster Federation: Allows the synchronization of resources across multiple clusters.
- 5. 16. Windows in Kubernetes: ● Windows Nodes: Support for Windows worker nodes and Windows containers in Kubernetes. 17. Kubernetes Testing: ● Kubetest: Kubernetes end-to-end testing. 18. Kubernetes Add-ons: ● DNS: DNS server for service name resolution. ● Web UI (Dashboard): Web-based Kubernetes user interface. ● Container Resource Monitoring: Time-series monitoring of resource utilization. ● Cluster-level Logging: Save container logs to a logging backend. 19. Other Essential Concepts: ● Quotas: Constraints applied to resources like Pods, Persistent Volumes. ● Annotations: Attach arbitrary non-identifying metadata to objects. ● Labels and Selectors: Labels are key/value pairs attached to objects and selectors are used to select objects based on labels. ● Liveness and Readiness Probes: Health checks for running applications. 20. Kubernetes Failure Handling: ● Pod Disruption Budgets (PDBs): Provides constraints that limit voluntary disruptions for Pods. 21. Kubernetes Architecture Concepts: ● Cloud Controller Manager: Embeds cloud-specific control logic for the cloud provider. ● Kube-Proxy: Maintains network rules and enables connection forwarding. ● Container Runtime: The software used to run containers, e.g., Docker, containers.
- 6. 22. Kubernetes Community and Development: ● Special Interest Groups (SIGs): The Kubernetes project is divided into several Special Interest Groups or SIGs. ● Contributing to Kubernetes: Guide to becoming an active contributor to the Kubernetes project. 23. Kubernetes Best Practices: ● Logging Best Practices: Guidelines for logging in Kubernetes. ● Monitoring Best Practices: Guidelines for monitoring in Kubernetes. ● Security Best Practices: Guidelines for securing your applications in Kubernetes. ● Performance Best Practices: Guidelines for ensuring optimal performance in Kubernetes. 24. Kubernetes Automation and Autoscaling: ● Cluster Autoscaler: Automatically adjusts the size of the cluster, scaling it up or down as necessary. ● Vertical Pod Autoscaler: Automatically adjusts the amount of CPU and memory requested by containers in a Pod. ● Horizontal Pod Autoscaler (HPA): Automatically scales the number of Pods in a deployment or replica set based on observed CPU or memory utilization. 25. Kubernetes Development Tools: ● Minikube: Runs a single-node Kubernetes cluster inside a VM on your laptop for users looking to try out Kubernetes or develop with it day-to-day. ● Skaffold: Command line tool that facilitates continuous development for Kubernetes applications. ● Kompose: Conversion tool for all Docker Compose users to help them move to Kubernetes. ● Kubeadm: Tool for bootstrapping a best-practice Kubernetes cluster.
- 7. 26. Advanced Kubernetes Networking: ● Network Plugins: Extend Kubernetes networking. ● CNI (Container Network Interface): Standard for writing plugins to configure network interfaces in Linux containers. ● Flannel: Overlay network provider. ● Calico: Provides secure network connectivity. 27. Kubernetes Performance Tuning: ● Kubelet Garbage Collection: Cleanup of unused images or containers. ● Kernel Tuning: Adjusting Linux kernel parameters to optimize performance. 28. Kubernetes Service Mesh: ● Istio: Open platform to connect, manage, and secure microservices. ● Linkerd: Another popular service mesh for Kubernetes.
- 8. Kubernetes Commands & Usages: 1- Basic Cluster Information: ○ kubectl cluster-info: Display information about the cluster. ○ kubectl version: Display version info. 2- Working with Nodes and Cluster: ○ kubectl get nodes: List nodes in a cluster. ○ kubectl describe node <node-name>: Show details of a specific node. 3- Working with Pods: ○ kubectl get pods: List all pods in all namespaces. ○ kubectl run <name> --image=<image>: Deploy a new Pod with a given image. ○ kubectl describe pod <pod-name>: Describe a specific pod. ○ kubectl logs <pod-name>: Fetch the logs from a pod. ○ kubectl delete pod <pod-name>: Delete a specific pod. 4- Working with Deployments: ○ kubectl create deployment <name> --image=<image>: Create a new deployment. ○ kubectl get deployments: List all deployments. ○ kubectl describe deployment <deployment-name>: Describe a specific deployment. ○ kubectl scale deployment <deployment-name> --replicas=<num>: Scale up/down a deployment. 5- Working with Services: ○ kubectl expose deployment <name> --type=LoadBalancer --port=8080: Expose a deployment as a service. ○ kubectl get services: List all services. ○ kubectl describe service <service-name>: Describe a specific service.
- 9. 6- Config and Storage: ○ kubectl get configmaps: List all config maps. ○ kubectl create configmap <name> --from-file=<path>: Create a config map from a file. ○ kubectl get secrets: List all secrets. ○ kubectl create secret: Create a secret. ○ kubectl get pv: List all persistent volumes. ○ kubectl get pvc: List all persistent volume claims. 7- Namespaces and Context: ○ kubectl get namespaces: List all namespaces. ○ kubectl config get-contexts: Show all contexts. ○ kubectl config use-context <context-name>: Switch to a different context. 8- Others: ○ kubectl apply -f <filename>: Apply a configuration from a file. ○ kubectl delete -f <filename>: Delete resources defined in a file. ○ kubectl exec -it <pod-name> -- /bin/sh: Execute a command inside a running pod. ○ kubectl port-forward <pod-name> <local-port>:<pod-port>: Forward a port from a running pod to a local port. 9- Advanced: ○ kubectl get all: List all resources. ○ kubectl rollout status deployment/<deployment-name>: View the rollout status of a deployment. ○ kubectl rollout history deployment/<deployment-name>: View the history of a deployment. ○ kubectl rollout undo deployment/<deployment-name>: Rollback to a previous version of a deployment.
- 10. 10- Monitoring & Logging: ● kubectl top nodes: Display resource (CPU/Memory/Storage) usage of nodes. ● kubectl top pods: Display resource (CPU/Memory/Storage) usage of pods. 11- Autoscaling: ● kubectl autoscale deployment <deployment-name> --min=<min-pods> --max=<max-pods> --cpu-percent=<cpu-util-percentage>: Auto scale a deployment based on CPU utilization. 12- Working with Helm: ● helm list: List releases. ● helm install <chart>: Install a helm chart. ● helm uninstall <release-name>: Uninstall a helm release. 13- Using Network Policies: ● kubectl get networkpolicies: List all network policies. ● kubectl describe networkpolicy <policy-name>: Describe a specific network policy. 14- Using CronJobs and Jobs: ● kubectl get cronjobs: List all cronjobs. ● kubectl get jobs: List all jobs. ● kubectl logs job/<job-name>: Fetch logs from a job. 15- Working with RBAC: ● kubectl get roles: List all roles in the current namespace. ● kubectl get clusterroles: List all cluster roles. 16- Using kubectl Plugins: ● kubectl krew search: Search plugins available for kubectl. ● kubectl krew install <plugin-name>: Install a kubectl plugin.