k3s deepdive

gistfile1.txt

Katakoda Ubuntu Playground 
https://www.katacoda.com/courses/ubuntu/playground

Install k3s
curl -sfL https://get.k3s.io | sh - 
export KUBECONFIG=/etc/rancher/k3s/k3s.yaml

Rancher deployment:
---
kind: Namespace
apiVersion: v1
metadata:
  name: cattle-system
  labels:
    name: cattle-system

---
kind: ServiceAccount
apiVersion: v1
metadata:
    name: cattle-admin
    namespace: cattle-system
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
    name: cattle-crb
    namespace: cattle-system
subjects:
  - kind: ServiceAccount
    name: cattle-admin
    namespace: cattle-system
roleRef:
    kind: ClusterRole
    name: cluster-admin
    apiGroup: rbac.authorization.k8s.io

---
kind: Deployment
apiVersion: apps/v1
metadata:
    namespace: cattle-system
    name: cattle
spec:
    replicas: 1
    selector:
      matchLabels:
        app: cattle
    template:
      metadata:
        labels:
          app: cattle
      spec:
        serviceAccountName: cattle-admin
        containers:
        - image: rancher/rancher:v2.3.0
          imagePullPolicy: Always
          name: cattle-server
          ports:
          - containerPort: 80
            protocol: TCP
          - containerPort: 443
            protocol: TCP
          volumeMounts:
          - mountPath: /var/lib/rancher
            name: rancher
        volumes:
        - name: rancher
          hostPath:
            path: /home/rancher
---
apiVersion: v1
kind: Service
metadata:
  namespace: cattle-system
  name: cattle-service
spec:
  ports:
    - name: http
      port: 80
    - name: https
      port: 443
  selector:
    app: cattle


---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: cattle-ingress
  namespace: cattle-system
  annotations:
    kubernetes.io/ingress.class: traefik
spec:
  rules:
  - http:
      paths:
      - path: /
        backend:
          serviceName: cattle-service
          servicePort: http
          
          
          
FAQ:
why k3s on IOT
devops for IOT
ha, scalibility, efficient use deployment to IOt edge

HA architecture
https://rancher.com/docs/k3s/latest/en/architecture/#high-availability-with-an-external-db
Agents will register with the server using the node cluster secret along with a randomly generated password for the node,
stored at /etc/rancher/node/password. The server will store the passwords for individual nodes at
/var/lib/rancher/k3s/server/cred/node-passwd, and any subsequent attempts must use the same password.


Why K3s:
for speed, easy to setup, easy to use, save cost, best for edge devices
why sqlitee over etcd
It's small. I've been experimenting with different backends for storage. To me SQL makes the most sense as I have a lot of flexibility. So I can do embedded with sqlite, I can get a hosted version of something with RDS, I can run mysql/postgres myself, I can run newsql like CockroachDB or TiDB.