= k3s =
 * k3s  - Lightweight Kubernetes
 * https://k3s.io/
 * https://github.com/rancher/k3s/releases/tag/v1.17.0+k3s.1
 * https://rancher.com/docs/k3s/latest/en/
 * https://rancher.com/docs/k3s/latest/en/quick-start/

K3S works great from something as small as a Raspberry Pi to an AWS a1.4xlarge 32GiB server.
Download k3s - latest release, x86_64, ARMv7, and ARM64 are supported
Situations where a PhD in k8s clusterology is infeasible

{{{#!highlight bash
curl -sfL https://get.k3s.io | sh -
sudo curl -sfL https://get.k3s.io | sh -
# [INFO]  Finding latest release
# [INFO]  Using v1.17.0+k3s.1 as release
# [INFO]  Downloading hash https://github.com/rancher/k3s/releases/download/v1.17.0+k3s.1/sha256sum-amd64.txt
# [INFO]  Downloading binary https://github.com/rancher/k3s/releases/download/v1.17.0+k3s.1/k3s
# [INFO]  Verifying binary download
# [INFO]  Installing k3s to /usr/local/bin/k3s
# [INFO]  Creating /usr/local/bin/kubectl symlink to k3s
# [INFO]  Creating /usr/local/bin/crictl symlink to k3s
# [INFO]  Creating /usr/local/bin/ctr symlink to k3s
# [INFO]  Creating killall script /usr/local/bin/k3s-killall.sh
# [INFO]  Creating uninstall script /usr/local/bin/k3s-uninstall.sh
# [INFO]  env: Creating environment file /etc/systemd/system/k3s.service.env
# [INFO]  systemd: Creating service file /etc/systemd/system/k3s.service
# [INFO]  systemd: Enabling k3s unit
# Created symlink /etc/systemd/system/multi-user.target.wants/k3s.service → /etc/systemd/system/k3s.service.
# [INFO]  systemd: Starting k3s
# as root
k3s kubectl cluster-info
kubectl create deployment springboot-test --image=vbodocker/springboot-test:latest
kubectl expose deployment springboot-test --port=8000 --target-port=8080 --type=NodePort
kubectl get services
IP_SPRINGBOOT=$(kubectl get services | grep springboot | awk '//{print $3}')
curl http://$IP_SPRINGBOOT:8000/dummy
# list containerd images and containers
k3s crictl images
k3s crictl ps
# connect to container id
crictl exec -it 997a2ad8c763a  sh
# connect to container/pod
kubectl get pods
kubectl exec -it springboot-test-6bb5fdfc48-phh8k  sh
cat /etc/os-release # alpine linux in container
# give sudo rights to user
/sbin/usermod -aG sudo user
# scale pods
sudo kubectl scale deployment springboot-test --replicas=3
sudo kubectl get pods -o wide
# add mariadb pod/service
sudo kubectl create deployment mariadb-test --image=mariadb:latest
sudo kubectl get pods -o wide
sudo kubectl delete deployment mariadb-test
# https://kubernetes.io/docs/tasks/run-application/run-single-instance-stateful-application/
sudo kubectl apply -f mariadb-pv.yaml
#persistentvolume/mariadb-pv-volume created
#persistentvolumeclaim/mariadb-pv-claim created
sudo kubectl apply -f mariadb-deployment.yaml 
#service/mariadb created
#deployment.apps/mariadb created
sudo kubectl describe deployment mariadb
sudo kubectl get svc -o wide
# connect to mariabdb pod
sudo kubectl exec -it mariadb-8578f4dc8c-r4ftv /bin/bash
ss -atn # show ports tcp listening
ip address # show ip addresses
mysql -h localhost -p
mysql -u root -h 10.42.0.12 -p 

# delete service, persistent volume claim and persistent volume
sudo kubectl delete deployment,svc mariadb
sudo kubectl delete pvc mariadb-pv-claim
sudo kubectl delete pv mariadb-pv-volume
}}}

== mariadb-pv.yaml ==
{{{#!highlight yaml
apiVersion: v1
kind: PersistentVolume
metadata:
  name: mariadb-pv-volume
  labels:
    type: local
spec:
  storageClassName: manual
  capacity:
    storage: 1Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/mnt/data"
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mariadb-pv-claim
spec:
  storageClassName: manual
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi
}}}

== mariadb-deployment.yaml ==
{{{#!highlight yaml
apiVersion: v1
kind: Service
metadata:
  name: mariadb
spec:
  ports:
  - port: 3306
  selector:
    app: mariadb
  clusterIP: None
---
apiVersion: apps/v1 # for versions before 1.9.0 use apps/v1beta2
kind: Deployment
metadata:
  name: mariadb
spec:
  selector:
    matchLabels:
      app: mariadb
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: mariadb
    spec:
      containers:
      - image: mariadb:latest
        name: mariadb
        env:
          # Use secret in real usage
        - name: MYSQL_ROOT_PASSWORD
          value: password
        ports:
        - containerPort: 3306
          name: mariadb
        volumeMounts:
        - name: mariadb-persistent-storage
          mountPath: /var/lib/mariadb
      volumes:
      - name: mariadb-persistent-storage
        persistentVolumeClaim:
          claimName: mariadb-pv-claim
}}}

= Init containers =
 * https://kubernetes.io/docs/concepts/workloads/pods/init-containers/
Init containers can contain utilities or setup scripts not present in an app image.

= systemctl commands =
{{{#!highlight bash
systemctl start k3s
systemctl stop k3s
systemctl status k3s
systemctl disable k3s.service
systemctl enable k3s
}}}

= Ubuntu pod =
== ubuntu.yaml ==
{{{#!highlight yaml
apiVersion: v1
kind: Pod
metadata:
  name: ubuntu
  labels:
    app: ubuntu
spec:
  containers:
  - name: ubuntu
    image: ubuntu:latest
    command: ["/bin/sleep", "3650d"]
    imagePullPolicy: IfNotPresent
  restartPolicy: Always
}}}

{{{#!highlight bash
sudo kubectl apply -f ubuntu.yaml
sudo kubectl get pods
sudo kubectl exec -it ubuntu -- bash
sudo kubectl delete pod ubuntu
}}}

= Alpine pod =
== alpine.yaml ==
{{{#!highlight yaml
apiVersion: v1
kind: Pod
metadata:
  name: alpine
  labels:
    app: alpine
spec:
  containers:
  - name: alpine
    image: alpine:latest
    command: ["/bin/sleep", "3650d"]
    imagePullPolicy: IfNotPresent
  restartPolicy: Always
}}}
{{{#!highlight bash
# Pods use PersistentVolumeClaims to request physical storage.
sudo kubectl apply -f alpine.yaml
sudo kubectl exec -it alpine -- sh
}}}


= Nginx with persistent volume =
{{{#!highlight bash
cd /tmp
mkdir -p /tmp/data
echo 'Hello from Kubernetes storage' > /tmp/data/index.html
}}}

== pv-volume.yaml ==
{{{#!highlight yaml
apiVersion: v1
kind: PersistentVolume
metadata:
  name: task-pv-volume
  labels:
    type: local
spec:
  storageClassName: manual
  capacity:
    storage: 0.2Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/tmp/data"
}}}

== pv-claim.yaml ==
{{{#!highlight yaml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: task-pv-claim
spec:
  storageClassName: manual
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 0.2Gi
}}}

== pv-pod.yaml ==
{{{#!highlight yaml
apiVersion: v1
kind: Pod
metadata:
  name: task-pv-pod
spec:
  volumes:
    - name: task-pv-storage
      persistentVolumeClaim:
        claimName: task-pv-claim
  containers:
    - name: task-pv-container
      image: nginx
      ports:
        - containerPort: 80
          name: "http-server"
      volumeMounts:
        - mountPath: "/usr/share/nginx/html"
          name: task-pv-storage
}}}
{{{#!highlight bash
sudo kubectl apply -f pv-volume.yaml
sudo kubectl apply -f pv-claim.yaml
sudo kubectl apply -f pv-pod.yaml
sudo kubectl get pods -o wide 
curl http://10.42.0.28/
sudo kubectl exec -it task-pv-pod -- bash
cd /usr/share/nginx/html
echo "Hey from Kubernetes storage" > index.html
cat /etc/os-release # debian buster 
kubectl delete pod task-pv-pod
kubectl delete pvc task-pv-claim
kubectl delete pv task-pv-volume
cat /tmp/data/index.html 
}}}

= Generate yaml =
{{{#!highlight sh
sudo kubectl create deployment cherrypy-test --image=vbodocker/cherrypy-test --dry-run=client --output=yaml
sudo kubectl expose deployment cherrypy-test --port=8080 --type=NodePort --dry-run=client --output=yaml
sudo kubectl scale deployment cherrypy-test --replicas=3 --dry-run=client --output=yaml
}}}

= Alpine persistent volume =
== alpine-shared.yaml ==
{{{#!highlignt yaml
---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: alpine-pv-volume
  labels:
    type: local
spec:
  storageClassName: manual
  capacity:
    storage: 0.2Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/tmp/alpine-data"
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: alpine-pv-claim
spec:
  storageClassName: manual
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 0.2Gi
---
apiVersion: v1
kind: Pod
metadata:
  name: alpine-pod
  labels:
    app: alpine-pod
spec:
  volumes:
    - name: alpine-pv-storage
      persistentVolumeClaim:
        claimName: alpine-pv-claim
  containers:
  - name: alpine
    image: alpine:latest
    command: ["/bin/sleep", "3650d"]
    imagePullPolicy: IfNotPresent
    volumeMounts:
      - mountPath: "/mnt/alpine/data"
        name: alpine-pv-storage
  restartPolicy: Always
}}}
{{{#!highlight bash
mkdir -p /tmp/alpine-data/
sudo kubectl apply -f alpine-shared.yaml 
sudo kubectl exec -it alpine-pod -- sh
# inside pod
cd /mnt/alpine/data # inside pod
echo "teste" > x.txt # inside pod
# in host
cat /tmp/alpine-data/x.txt # k8s host
}}}

= MariaDB + NFS =
{{{#!highlight sh
/vol *(rw,sync,insecure,fsid=0,no_subtree_check,no_root_squash)
exportfs -rav
exporting *:/vol
mkdir -p /vol/mariadb-0

kubectl apply -f mariadb-nfs.yaml
kubectl exec -it mariadb-79847f5d97-smbdx -- bash
touch  /var/lib/mariadb/b
mount | grep nfs
kubectl delete -f mariadb-nfs.yaml
kubectl get pods
kubectl get pvc
kubectl get pv
}}}

== mariadb-nfs.yaml ==
{{{#!highlight yaml
---
apiVersion: v1
kind: PersistentVolume
metadata:
  name: mdb-vol-0
  labels:
    volume: mdb-volume
spec:
  storageClassName: manual
  capacity:
    storage: 1Gi
  accessModes:
    - ReadWriteOnce
  nfs:
    server: 127.0.0.1
    path: "/vol/mariadb-0"
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mdb-pv-claim
spec:
  storageClassName: manual
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi
---
apiVersion: v1
kind: Service
metadata:
  name: mariadb
spec:
  ports:
  - port: 3306
  selector:
    app: mariadb
  clusterIP: None
---
apiVersion: apps/v1 # for versions before 1.9.0 use apps/v1beta2
kind: Deployment
metadata:
  name: mariadb
spec:
  selector:
    matchLabels:
      app: mariadb
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: mariadb
    spec:
      containers:
      - image: mariadb:latest
        name: mariadb
        env:
          # Use secret in real usage
        - name: MYSQL_ROOT_PASSWORD
          value: password
        ports:
        - containerPort: 3306
          name: mariadb
        volumeMounts:
        - name: mdb-persistent-storage
          mountPath: /var/lib/mariadb
      volumes:
      - name: mdb-persistent-storage
        persistentVolumeClaim:
          claimName: mdb-pv-claim
}}}

= Persistent volumes =
 * https://kubernetes.io/docs/concepts/storage/persistent-volumes/

A PersistentVolume (PV) is a piece of storage in the cluster that has been provisioned by an administrator or dynamically provisioned using Storage Classes.

A PersistentVolumeClaim (PVC) is a request for storage by a user.
 
Pods consume node resources and PVCs consume PV resources. Claims can request specific size and access modes (e.g., they can be mounted ReadWriteOnce, ReadOnlyMany or ReadWriteMany, see AccessModes).

Types of Persistent Volumes:
 * local - local storage devices mounted on nodes.
 * nfs - Network File System (NFS) storage


= Ingress controller nginx example =

== ingress-cherrypy-test.yml ==
{{{#!highlight yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: ingress-cherrypy-test
spec:
  rules:
  - host: cp.info
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: cherrypy-test
            port:
              number: 8000
  ingressClassName: nginx
}}}

== Steps ==
{{{#!highlight bash
# install k3s
curl -sfL https://get.k3s.io | sh -
KUBECONFIG=~/.kube/config
mkdir ~/.kube 2> /dev/null
sudo k3s kubectl config view --raw > "$KUBECONFIG"
chmod 600 "$KUBECONFIG"
nano ~/.bashrc 
export KUBECONFIG=~/.kube/config
source . ~/.bashrc 

sudo nano /etc/systemd/system/k3s.service
ExecStart=/usr/local/bin/k3s server --write-kubeconfig-mode=644
sudo systemctl daemon-reload
sudo service k3s start
sudo service k3s status
kubectl get pods 

k3s kubectl cluster-info 

kubectl -n kube-system delete helmcharts.helm.cattle.io traefik
sudo service k3s stop
sudo nano /etc/systemd/system/k3s.service
# ExecStart=/usr/local/bin/k3s server --write-kubeconfig-mode=644 --no-deploy traefik 
sudo systemctl daemon-reload
sudo rm /var/lib/rancher/k3s/server/manifests/traefik.yaml
sudo service k3s start
kubectl -n kube-system delete helmcharts.helm.cattle.io traefik
sudo systemctl restart k3s

kubectl get nodes 
kubectl delete node localhost 
kubectl get pods --all-namespaces 
kubectl get services --all-namespaces
kubectl get deployment --all-namespaces

# install nginx ingress controller 
kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/controller-v1.4.0/deploy/static/provider/cloud/deploy.yaml
kubectl get pods --namespace=ingress-nginx

kubectl create deployment cherrypy-test --image=vbodocker/cherrypy-test
kubectl expose deployment cherrypy-test --port=8000 --target-port=8080 --type=ClusterIP # cluster ip port 8000
kubectl get services

kubectl apply -f ingress-cherrypy-test.yml

EXTERNAL_IP=$(ip addr show | grep wlp | grep inet | awk '//{print $2}' | sed 's/\// /g' | awk '//{print $1}')
echo $EXTERNAL_IP
sudo sh -c " echo '$EXTERNAL_IP cp.info' >> /etc/hosts  "
kubectl get ingress 
curl cp.info 

kubectl scale deployment cherrypy-test --replicas=5
curl http://cp.info/ -vvv
sudo apt install apache2-utils
ab -n 10 -c 10 http://cp.info/

# Push image to docker hub
docker build -t vbodocker/cherrypy-test . 
docker run -p 8080:8080 vbodocker/cherrypy-test 
docker login # login to docker hub
docker push vbodocker/cherrypy-test 
docker pull vbodocker/cherrypy-test:latest

# Rollout, deploy new image
kubectl get deployments -o wide # shows image urls 
kubectl rollout restart deployment cherrypy-test # redeploy image url for cherrypy-test
kubectl rollout status deployment cherrypy-test
kubectl get deployments -o wide 
kubectl get pods -o wide # age should be low for the newly deployed pods 
}}}

= Install k3s static binary in Slack64 =
 * https://github.com/k3s-io/k3s#k3s---lightweight-kubernetes
 * Binaries available in https://github.com/k3s-io/k3s#manual-download 
 * wget https://github.com/k3s-io/k3s/releases/download/v1.25.3%2Bk3s1/k3s

{{{#!highlight sh
sudo mv ~/Downloads/k3s /usr/bin/
sudo chmod 744 /usr/bin/k3s
}}}

== /etc/rc.d/rc.k3s ==
{{{#!highlight sh
#!/bin/sh
PATH=$PATH:/usr/sbin

k3s_start() {
  /usr/bin/k3s server --write-kubeconfig-mode=644 \
  --disable traefik > /var/log/k3s.log 2>&1 &
}

k3s_stop() {
  kill $(ps uax | grep "/usr/bin/k3s" | head -1 | awk '//{print $2}')
  ps uax | grep containerd | awk '//{print $2}' | xargs -i kill {}
}

k3s_restart() {
  k3s_stop
  k3s_start
}

case "$1" in
'start')
  k3s_start
  ;;
'stop')
  k3s_stop
  ;;
'restart')
  k3s_restart
  ;;
*)
  echo "usage $0 start|stop|restart"
esac
}}}

== ingress-cherrypy-test.yml ==
{{{#!highlight yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: ingress-cherrypy-test
spec:
  rules:
  - host: cp.info
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: cherrypy-test
            port:
              number: 8000
  ingressClassName: nginx
}}}

== Steps ==
{{{#!highlight sh
echo "alias kubectl='/usr/bin/k3s kubectl'" >> ~/.bashrc
source ~/.bashrc
sudo sh /etc/rc.d/rc.k3s start
kubectl get nodes
kubectl get deployments --all-namespaces
kubectl get services --all-namespaces
kubectl get pods --all-namespaces
kubectl cluster-info 
# install nginx ingress controller
kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/controller-v1.4.0/deploy/static/provider/cloud/deploy.yaml 
# wait for nginx ingress controller to finish 
sleep 120
kubectl create deployment cherrypy-test --image=vbodocker/cherrypy-test
kubectl expose deployment cherrypy-test --port=8000 --target-port=8080 --type=ClusterIP
kubectl get pods --all-namespaces
kubectl get services --all-namespaces
kubectl apply -f ingress-cherrypy-test.yml 
EXTERNAL_IP=$(/sbin/ip addr show | grep wl | grep inet | awk '//{print $2}' | sed 's/\// /g' | awk '//{print $1}')
echo $EXTERNAL_IP
sudo sh -c " echo '$EXTERNAL_IP cp.info' >> /etc/hosts  "
cat /etc/hosts
kubectl get ingress 
curl cp.info 
}}}

== Local docker registry example ==

=== Dockerfile ===
{{{#!highlight sh
FROM alpine:3.16
RUN apk add --update --no-cache python3 nano py3-pip
RUN pip install cherrypy routes --user
RUN mkdir /app
COPY . /app/
WORKDIR /app
CMD ["python3","main.py"]
}}}

=== main.py ===
{{{#!highlight python
import cherrypy
import wsgiref.handlers
import time
import socket 

class RootUrl:
  @cherrypy.expose
  def index(self):
    return "Hello world ola mundo %s"%(socket.gethostname())

def main():
  ru = RootUrl()
  cherrypy.server.socket_host = '0.0.0.0'
  cherrypy.quickstart(ru) 

if __name__ == '__main__':
  main()
}}}

=== test-py.yaml ===
{{{#!highlight yaml
apiVersion: v1
kind: Service
metadata:
  name: test-py-svc
spec:
  ports:
  - port: 8080
  selector:
    app: test-py-deploy
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: test-py-deploy
spec:
  selector:
    matchLabels:
      app: test-py-deploy
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: test-py-deploy
    spec:
      containers:
      - image: localhost:5000/test-py-image:latest
        name: test-py
        ports:
        - containerPort: 8080
          name: test-py
      imagePullSecrets:
      - name: regcred
}}}

=== ingress-test-py.yaml ===
{{{#!highlight yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: ingress-test-py
spec:
  rules:
  - host: testpy.info
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: test-py-svc
            port:
              number: 8080
  ingressClassName: nginx
}}}

=== Steps ===
{{{#!highlight sh
mkdir test-py
cd test-py
mkdir auth
docker run --entrypoint htpasswd httpd:2 -Bbn testuser testpassword > auth/htpasswd
docker run -d -p 5000:5000 --restart=always --name registry -v "$(pwd)"/auth:/auth \
  -e "REGISTRY_AUTH=htpasswd" -e "REGISTRY_AUTH_HTPASSWD_REALM=Registry Realm" \
  -e REGISTRY_AUTH_HTPASSWD_PATH=/auth/htpasswd \
  registry:2
docker ps
curl http://testuser:testpassword@localhost:5000/v2/_catalog

docker build -t test-py-image .
docker login localhost:5000
docker tag test-py-image localhost:5000/test-py-image
docker push localhost:5000/test-py-image

kubectl delete secret regcred
kubectl create secret docker-registry regcred --docker-server=localhost:5000 --docker-username=testuser --docker-password=testpassword --docker-email=test@example.org

kubectl apply -f test-py.yaml
curl $(kubectl get services | grep test | awk '//{print $3}'):8080
# Hello world ola mundo test-py

kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/controller-v1.4.0/deploy/static/provider/cloud/deploy.yaml 
# wait for nginx ingress controller to finish 
sleep 120

EXTERNAL_IP=$(/sbin/ip addr show | grep wl | grep inet | awk '//{print $2}' | sed 's/\// /g' | awk '//{print $1}')
echo $EXTERNAL_IP
sudo sh -c " echo '$EXTERNAL_IP testpy.info' >> /etc/hosts  "
kubectl apply -f ingress-test-py.yaml
curl testpy.info
}}}

== DNS issues ==
k3s DNS resides in namespace kube-system in the service kube-dns
{{{#!highlight sh
# kube-system kube-dns  ClusterIP 10.43.0.10
# tests in pods IP 10.43.0.10
nslookup <service>.<namespace>.svc.cluster.local 10.43.0.10
nslookup api.chucknorris.io  10.43.0.10
# add Google and cloudfare entries
KUBE_EDITOR="nano" kubectl -n kube-system edit configmap coredns
forward . 1.1.1.1 8.8.8.8 /etc/resolv.conf
# Redeploy coredns
kubectl -n kube-system rollout restart deployment coredns
# Check logs 
kubectl logs --namespace=kube-system --tail=100 -l k8s-app=kube-dns
}}}