Kubernetes¶

Kubernetes (or "k8s") is a container orchestration system for automating application deployment, scaling, and management.

It solves many problems that arise from managing containerized applications at scale.

Table of Contents¶

k3s
kubectl
k3s Exercise: Setting up a Small Cluster
Helm

k3s¶

k3s is a fully compliant Kubernetes distribution designed to be extremely lightweight.
It ships as a single binary and it's incredibly easy to install on most platforms.

With k3s, you sacrifice the deep granularity and control that you get from k8s.

To install k3s:

curl -sFL https://get.k3s.io | sh -  # Install k3s
# or, if that doesn't work
curl -sL https://get.k3s.io | sh -   # Install k3s

-s: Silent mode.
-F: Emulates pressing Submit on a filled-in form.
-L: Follows redirects.

`kubectl`¶

kubectl (Kube Control) is the command-line interface for interacting with Kubernetes clusters.

Also see kubectl commands

kubectl version
kubectl get nodes
kubectl get pods -A  # Get all pods from all namespaces
kubectl get ns       # Show all the namespaces
kubectl get pods -n kube-system # scope down to the kube-system namespace
kubectl get pods -n kube-system -o wide # scope down to the kube-system namespace
kubectl get pods -n kube-system -o wide --show-labels # scope down to the kube-system namespace

k3s Exercise: Setting up a Small Cluster¶

Create a pod named 'webpage' with the image 'nginx'
```
kubectl run webpage --image=nginx  
```
Create a pod named database with the redis image, and set to tier=database.
```
kubectl run database --image=redis --labels=tier=database
```
Create a service wit hthe name redis-service to expose the database pod within the cluster on port 6379, which is the default redis port.
```
kubectl expose pod database --port=6379 --name=redis-service --type=ClusterIP
```
Create a deployment called web-deployment using the image nginx that has 3 replicas.
```
kubectl create deployment web-deployment --image=nginx --replicas=3
```

Verify that the pods are created

kubectl get deployments
kubectl get pods

Create a new namespace called webns
```
kubectl create namespace webns
```
Create a new deployment called redis-deploy with the image redis in the webns namespace with 2 replicas.
```
kubectl create deployment redis-deploy --image=redis -n webns --replicas=2
```

Helm¶

Helm is a package manager for Kubernetes. Helm uses what they call "Helm Charts."

Helm charts are a way to define/simplify deployment and management of applications with Kubernetes.

A helm chart is a package that contains three main components:

Templates: YAML files for Kubernetes manifests, which can be deployments, services, configMaps, secrets, etc.
Values: Config files that allow for customization without modifying the templates themselves
Metadata: Info about the chart (version, app name, etc.)

Bit of history: k8s had an uwu version: Kubernetes v1.30: Uwubernetes