Kubernetes Zero To Pro ✨

⛏️ “A stone is broken by the last stroke of the hammer. This does not mean that the first stroke was useless. Success is the result of continuous effort.” ⛏️

Table of `Contents` 📜

🗃️ resources
🧠 core concepts
- 🐋 pods
- 👯 replica sets and replication controllers
- 🚀 deployments
- 🖧 networking
- 🛎️ services
- 🏗️ microservice architecture
- ☁️ cloud
- 📛 namespaces
- 🧙 imperative commands
⚙️ configuration
- 🔣 container arguments
- 🗺️ configmaps
- 🕵️ secrets
- 💁 service accounts
- 💾 resource requirements
- ☢️ taints and tolerations
- 🔘 node selectors and affinity
🐳^🐳 multi-container pods
- 🐳^🐳 multi-container pods
- 💥 init containers
🔬 observability
- 🛸 readiness and liveness probes
- 📄 container logging
- 🕸️ monitor and debug apps
💠 pod design
- 🏷️ labels selectors and annotations
- 👔 jobs
- ⏳ cron jobs
🤯 advanced services and networking
- ⚖️ ingress networking
- 🤝 network policies
🗄️ state persistence
- 💾 volumes
- 🏰 persistent volumes
- 🚩 persistent volume claims
- 📦 storage classes
- 🌟 stateful sets
- 🧟 headless service

Kubernetes `Architecture` 🏗️

Kubernetes coordinates a highly available cluster of computers that are connected to work as a single unit.

The Control Plane is responsible for managing the cluster.
- Components
  - kube-apiserver - Exposes the Kubernetes API
  - etcd - Consistent and highly-available key value store used as Kubernetes’ backing store for all cluster data.
  - kube-scheduler - Watches for newly created Pods with no assigned node, and selects a node for them to run on.
  - kube-controller-manager - Runs controller processes. Each controller is a separate process but to keep things simple they are compiled together and run in a single process
    - Examples
      - Node controller: Responsible for noticing and responding when nodes go down.
      - Job controller: Watches for Job objects that represent one-off tasks, then creates Pods to run those tasks to completion.
      - Endpoints controller: Populates the Endpoints object (that is, joins Services & Pods).
      - Service Account & Token controllers: Create default accounts and API access tokens for new namespaces
  - cloud-controller-manager - Embeds cloud-specific control logic
    - Node, Route, and Service controllers can have cloud provider dependencies.

A Node is a VM or a physical computer that serves as a worker machine in a Kubernetes cluster.
- The nodes communicate with the control plane using the Kubernetes API
- Components
  - kubelet - An agent that runs on each node in the cluster. It makes sure that containers are running in a Pod.
    - kube-proxy - Network proxy that runs on each node in your cluster, implementing part of the Kubernetes Service concept.
  - Container runtime - Software that is responsible for running containers.

Basic `Commands` 📝

kubectl commands
- check version of Kubernetes being used
```
kubectl version
```
- get everything
```
kubectl get all
```
- get api resources includes name, shortnames, api version, if namespaced, and kind
```
kubectl api-resources
```
- get kube-api version
```
kubectl api-versions
```
- all resources in kubernetes are grouped into API groups
  - under each API group are API resources
    kubectl api-resources
    - API resources are the objects that can be have verbs act on them from the Kubernetes API
      - verbs: create, get, describe, delete, update, watch, list
- identify kube-apiserver settings
```
kubectl describe pod kube-apiserver-controlplane -n kube-system
```
minikube commands
- Check the status of minikube
```
minikube status
```
- start minikube
```
minikube start
```
- stop minikube
```
minikube stop
```