Resource

1 - An object of a certain type in the kubernetes API. 2 - You can list all available resources with kubectl api-resources. 3 - You can create your own custom resources using Custom Resource Definitions (CRDs). 4 - Use an init container to run a task before a Pod starts.

Pods management resources

1 - ReplicaSet - Ensures a specified number of pod replicas are running at any given time. 2 - Deployment - Manages ReplicaSets and provides declarative updates for Pods. 3 - Imperative command to create a Deployment: kubectl create deployment nginx --image=nginx --replicas=3 4 - StatefulSet - Manages stateful applications, providing stable network IDs and persistent storage.

DaemonSet - Dynamically runs a copy of a Pod on all or selected nodes in the cluster.

Job - Runs a task once.

CronJob - Runs a task periodically.

Kubernetes Architecture

1 - Worker Nodes - Responsible for running containers. 2 - Control Plane - Manages the cluster, including the API server, scheduler, and controller manager. 3 - API Server (Control Plane) - Provides a unified interface for interacting with the cluster. 4 - Scheduler (Control Plane) - Assigns Pods to Nodes. 5 - Controller Manager (Control Plane) - Runs controllers that manage the cluster state. 6 - etcd (Control Plane) - Stores cluster state. 7 - Cloud Controller Manager (Control Plane) - Manages cloud provider features. 8 - kube-proxy (Worker Nodes) - Provides network routing and load balancing for Pods. 9 - Container Runtime (Worker Nodes) - Runs containers. 10 - kubelet (Worker Nodes) - Agent that runs Pods and provides runtime features. 11 - Kubernetes CRI - Interface between container runtime and kubelet. 12 - kubelet no longer uses dockershim to support Docker, since Docker does not implement the CRI.

Kubernetes API

1 - REST API - A set of endpoints that can be used to interact with the Kubernetes API. 2 - Kubernetes API Server - The server that exposes the Kubernetes API. 3 - Formats: JSON, YAML - The formats used to define Kubernetes resources.

Containers

1 - Linux control groups (cgroups) - Used to provide container isolation. 2 - You can have more then one container in a Pod. 3 - A Dockerfile is a text document that contains all the commands a user could call on the command line to assemble an image.

Scheduling

1 - Scheduling is the process of assigning Pods to Nodes. 2 - Scheduling occurs when a new Pod is created or when a Node is added to the cluster. 3 - Scheduler takes into account things like resources requirements, Pod affinity, and tolerations when selecting a Node for a Pod.