# Kubernetes Tutorial

## setup
[reference](https://hackmd.io/@gdsc-ntcu/k8s)

### k8s installation (all nodes)

# uninstall k8s
sudo systemctl stop kubelet
sudo kubeadm reset
sudo apt-get purge kubeadm kubectl kubelet kubernetes-cni kube*
sudo apt-get autoremove
sudo rm -rf $HOME/.kube
sudo rm -rf /etc/cni/net.d
sudo iptables --flush

# install k8s (v1.31)
sudo apt-get update
sudo apt-get install -y apt-transport-https ca-certificates curl gpg
curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.31/deb/Release.key | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg
echo 'deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.31/deb/ /' | sudo tee /etc/apt/sources.list.d/kubernetes.list
sudo apt-get update
sudo apt-get install -y kubelet kubeadm kubectl
sudo apt-mark hold kubelet kubeadm kubectl
sudo systemctl enable --now kubelet

### container runtime installation (all nodes)

# uninstall docker
sudo systemctl stop docker
sudo systemctl stop containerd
sudo systemctl stop docker.socket
sudo apt-get purge -y docker.io
sudo apt-get purge -y docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin docker-ce-rootless-extras
dpkg -l | grep -i docker # see your installed packages

# install docker
# sudo apt-get install -y docker.io
sudo apt-get update
sudo apt-get install ca-certificates curl
sudo install -m 0755 -d /etc/apt/keyrings
sudo curl -fsSL https://download.docker.com/linux/ubuntu/gpg -o /etc/apt/keyrings/docker.asc
sudo chmod a+r /etc/apt/keyrings/docker.asc
echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/ubuntu \
  $(. /etc/os-release && echo "$VERSION_CODENAME") stable" | \
  sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

# containerd setup
sudo mkdir /etc/containerd
sudo sh -c "containerd config default > /etc/containerd/config.toml"
sudo sed -i 's/ SystemdCgroup = false/ SystemdCgroup = true/' /etc/containerd/config.toml
sudo systemctl restart containerd
sudo systemctl restart kubelet

sudo docker info | grep -i cgroup # ensure docker use systemd cgroup driver

### machine setup (all nodes)

# machine setup
sudo swapoff -a
sudo nano /etc/fstab # any lines contain "swap"
sudo hostnamectl set-hostname <name> # set hostname on all nodes
sudo nano /etc/hosts # set dns on all nodes (192.168.50.119 master, ...)

# kernel module
cat <<EOF | sudo tee /etc/modules-load.d/k8s.conf
overlay
br_netfilter
EOF
sudo modprobe overlay
sudo modprobe br_netfilter

# kernel parameter
cat <<EOF | sudo tee /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-iptables  = 1
net.bridge.bridge-nf-call-ip6tables = 1
net.ipv4.ip_forward                 = 1
EOF
sudo sysctl --system

### cluster initialization

# pull image on master node
sudo kubeadm config images pull

# master node initialization
sudo kubeadm init \
    --apiserver-advertise-address=192.168.50.119 \
    --pod-network-cidr=10.244.0.0/16
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config

# cni (calico)
### modify calico.yaml first
### search "Auto-detect the BGP IP address.
### at the same level, insert:
### - name: IP_AUTODETECTION_METHOD
###   value: "interface=can-reach=8.8.8.8"
curl https://raw.githubusercontent.com/projectcalico/calico/v3.26.0/manifests/calico.yaml -O
kubectl apply -f calico.yaml

# worker node initialization
<provided kubeadm join command>

# check cluster status
kubectl get nodes # check joined worker nodes
kubectl get pods --all-namespaces # confirm the cluster is running
kubeadm token create --print-join-command # if you forgot the command

## K8s Installation Problem
- calico and coredns pods keep pending
- solution 1:

        sudo mkdir -p /etc/containerd/
        containerd config default | sudo tee /etc/containerd/config.toml

Add `SystemdCgroup = true` in `config.toml`, and then restart the containerd

        sudo systemctl daemon-reload
        sudo systemctl restart containerd

- solution 2:

        // before cluster initialization
        sudo systemctl restart containerd

[reference](https://github.com/labring/sealos/issues/834)
- a node's "calico-node-xxxxx" and "kube-proxy-xxxxx" keep crashLoopBackOff
- check the dns resolution of that node
- may need to add `8.8.8.8` or `8.8.4.4`
- can ping www.google.com

## Some Useful Command

kubectl create deployment <dp-name> --image=<image location>
kubectl expose deployment/<dp-name> --type="NodePort" --port <port>
kubectl exec -ti <pod name> -- bash
kubectl delete pods --field-selector status.phase=Failed
kubectl get nodes -o jsonpath='{.items[*].spec.podCIDR}'
kubectl cluster-info dump | grep -m 1 cluster-cidr

## Basic Tutorial
From kubernetes interactive tutorial
### Create a kubernetes cluster

minikube version
minikube start
kubectl version
kubectl cluster-info
kubectl get nodes

### Deploy an App

kubectl version
kubectl get nodes
kubectl create deployment kubernetes-bootcamp --image=gcr.io/google-samples/kubernetes-bootcamp:v1
kubectl get deployments
echo -e "\n\n\n\e[92mStarting Proxy. After starting it will not output a response. Please click the first Terminal Tab\n"; 
kubectl proxy
curl http://localhost:8001/version
export POD_NAME=$(kubectl get pods -o go-template --template '{{range .items}}{{.metadata.name}}{{"\n"}}{{end}}')
echo Name of the Pod: $POD_NAME
curl http://localhost:8001/api/v1/namespaces/default/pods/$POD_NAME/

### Explore your App

kubectl get pods
kubectl describe pods
echo -e "\n\n\n\e[92mStarting Proxy. After starting it will not output a response. Please click the first Terminal Tab\n"; kubectl proxy
export POD_NAME=$(kubectl get pods -o go-template --template '{{range .items}}{{.metadata.name}}{{"\n"}}{{end}}')
echo Name of the Pod: $POD_NAME
curl http://localhost:8001/api/v1/namespaces/default/pods/$POD_NAME/proxy/
kubectl logs $POD_NAME
kubectl exec $POD_NAME -- env
kubectl exec -ti $POD_NAME -- bash
cat server.js
curl localhost:8080
exit

### Expose your app publicly

kubectl get pods
kubectl get services
kubectl expose deployment/kubernetes-bootcamp --type="NodePort" --port 8080
kubectl get services
kubectl describe services/kubernetes-bootcamp
export NODE_PORT=$(kubectl get services/kubernetes-bootcamp -o go-template='{{(index .spec.ports 0).nodePort}}')
echo NODE_PORT=$NODE_PORT
curl $(minikube ip):$NODE_PORT
kubectl describe deployment
kubectl get pods -l app=kubernetes-bootcamp
kubectl get services -l app=kubernetes-bootcamp
export POD_NAME=$(kubectl get pods -o go-template --template '{{range .items}}{{.metadata.name}}{{"\n"}}{{end}}')
echo Name of the Pod: $POD_NAME
kubectl label pods $POD_NAME version=v1
kubectl describe pods $POD_NAME
kubectl get pods -l version=v1
kubectl delete service -l app=kubernetes-bootcamp
kubectl get services
curl $(minikube ip):$NODE_PORT
kubectl exec -ti $POD_NAME -- curl localhost:8080

### Scale up Your App

kubectl get deployments
kubectl get rs
kubectl scale deployments/kubernetes-bootcamp --replicas=4
kubectl get deployments
kubectl get pods -o wide
kubectl describe deployments/kubernetes-bootcamp
kubectl describe services/kubernetes-bootcamp
export NODE_PORT=$(kubectl get services/kubernetes-bootcamp -o go-template='{{(index .spec.ports 0).nodePort}}')
echo NODE_PORT=$NODE_PORT
curl $(minikube ip):$NODE_PORT
kubectl scale deployments/kubernetes-bootcamp --replicas=2
kubectl get deployments
kubectl get pods -o wide

### Updating Your App

kubectl get deployments
kubectl get pods
kubectl describe pods
kubectl set image deployments/kubernetes-bootcamp kubernetes-bootcamp=jocatalin/kubernetes-bootcamp:v2
kubectl get pods
kubectl describe services/kubernetes-bootcamp
export NODE_PORT=$(kubectl get services/kubernetes-bootcamp -o go-template='{{(index .spec.ports 0).nodePort}}')
echo NODE_PORT=$NODE_PORT
curl $(minikube ip):$NODE_PORT
kubectl rollout status deployments/kubernetes-bootcamp
kubectl describe pods
kubectl set image deployments/kubernetes-bootcamp kubernetes-bootcamp=gcr.io/google-samples/kubernetes-bootcamp:v10
kubectl get deployments
kubectl get pods
kubectl describe pods
kubectl rollout undo deployments/kubernetes-bootcamp
kubectl get pods
kubectl describe pods