Follow Kubernetes the Hard way
This article was written by just following Kelsey Hightower’s Kubernetes Hardway document to understand Kubernetes internal architecture.
Overview
Control plane
The control plane’s overview:
Each node on the control plane:
- etcd: Store cluster states
- 2379: Client API port
- 2380: Peer API port
- Kubernetes API Server
- 6443
- Scheduler
- Controller Manager
- nginx
- For HTTP heath check from GCP Load Balancer
Each middleware was installed by systemd.
Data plane
- containerd
- start from systemd
- container networking plugin
- See this article or this article for the overview of CNI
- bridge network configuration
- kubelet
- start from systemd
- kube-proxy
- start from systemd
- iptables mode
- Coredns
- In kubernetes
- CLIs
- runc
- crictl
- kubectl
Networking
- Pod to Pod: Use iptables by kube-proxy.
- But I can’t find iptable rules to route traffic for a k8s service
- Node to Node networking: Use VPC Routes
2. Client tools
brew install cfssl
> cfssl version
Version: 1.6.4
Runtime: go1.20.3
> cfssljson --version
Version: 1.6.4
Runtime: go1.20.3
3 Compute resources
Set up them by terraform. Change the compute resource names
- from worker-$n to k8s-worker-$n
- from controller-$n to k8s-controller-$n
4. Certificate authority
Certificate Authority
cat > ca-config.json <<EOF
{
"signing": {
"default": {
"expiry": "8760h"
},
"profiles": {
"kubernetes": {
"usages": ["signing", "key encipherment", "server auth", "client auth"],
"expiry": "8760h"
}
}
}
}
EOF
cat > ca-csr.json <<EOF
{
"CN": "Kubernetes",
"key": {
"algo": "rsa",
"size": 2048
},
"names": [
{
"C": "US",
"L": "Portland",
"O": "Kubernetes",
"OU": "CA",
"ST": "Oregon"
}
]
}
EOF
cfssl gencert -initca ca-csr.json | cfssljson -bare ca
The Admin Client Certificate
cat > admin-csr.json <<EOF
{
"CN": "admin",
"key": {
"algo": "rsa",
"size": 2048
},
"names": [
{
"C": "US",
"L": "Portland",
"O": "system:masters",
"OU": "Kubernetes The Hard Way",
"ST": "Oregon"
}
]
}
EOF
cfssl gencert \
-ca=ca.pem \
-ca-key=ca-key.pem \
-config=ca-config.json \
-profile=kubernetes \
admin-csr.json | cfssljson -bare admin
The Kubelet Client Certificates
for instance in k8s-worker-0 k8s-worker-1 k8s-worker-2; do
cat > ${instance}-csr.json <<EOF
{
"CN": "system:node:${instance}",
"key": {
"algo": "rsa",
"size": 2048
},
"names": [
{
"C": "US",
"L": "Portland",
"O": "system:nodes",
"OU": "Kubernetes The Hard Way",
"ST": "Oregon"
}
]
}
EOF
EXTERNAL_IP=$(gcloud compute instances describe ${instance} \
--format 'value(networkInterfaces[0].accessConfigs[0].natIP)')
INTERNAL_IP=$(gcloud compute instances describe ${instance} \
--format 'value(networkInterfaces[0].networkIP)')
cfssl gencert \
-ca=ca.pem \
-ca-key=ca-key.pem \
-config=ca-config.json \
-hostname=${instance},${EXTERNAL_IP},${INTERNAL_IP} \
-profile=kubernetes \
${instance}-csr.json | cfssljson -bare ${instance}
done
The Controller Manager Client Certificate
cat > kube-controller-manager-csr.json <<EOF
{
"CN": "system:kube-controller-manager",
"key": {
"algo": "rsa",
"size": 2048
},
"names": [
{
"C": "US",
"L": "Portland",
"O": "system:kube-controller-manager",
"OU": "Kubernetes The Hard Way",
"ST": "Oregon"
}
]
}
EOF
cfssl gencert \
-ca=ca.pem \
-ca-key=ca-key.pem \
-config=ca-config.json \
-profile=kubernetes \
kube-controller-manager-csr.json | cfssljson -bare kube-controller-manager
The Kube Proxy Client Certificate
cat > kube-proxy-csr.json <<EOF
{
"CN": "system:kube-proxy",
"key": {
"algo": "rsa",
"size": 2048
},
"names": [
{
"C": "US",
"L": "Portland",
"O": "system:node-proxier",
"OU": "Kubernetes The Hard Way",
"ST": "Oregon"
}
]
}
EOF
cfssl gencert \
-ca=ca.pem \
-ca-key=ca-key.pem \
-config=ca-config.json \
-profile=kubernetes \
kube-proxy-csr.json | cfssljson -bare kube-proxy
The Scheduler Client Certificate
cat > kube-scheduler-csr.json <<EOF
{
"CN": "system:kube-scheduler",
"key": {
"algo": "rsa",
"size": 2048
},
"names": [
{
"C": "US",
"L": "Portland",
"O": "system:kube-scheduler",
"OU": "Kubernetes The Hard Way",
"ST": "Oregon"
}
]
}
EOF
cfssl gencert \
-ca=ca.pem \
-ca-key=ca-key.pem \
-config=ca-config.json \
-profile=kubernetes \
kube-scheduler-csr.json | cfssljson -bare kube-scheduler
The Kubernetes API Server Certificate
KUBERNETES_PUBLIC_ADDRESS=$(gcloud compute addresses describe kubernetes-the-hard-way \
--region $(gcloud config get-value compute/region) \
--format 'value(address)')
KUBERNETES_HOSTNAMES=kubernetes,kubernetes.default,kubernetes.default.svc,kubernetes.default.svc.cluster,kubernetes.svc.cluster.local
cat > kubernetes-csr.json <<EOF
{
"CN": "kubernetes",
"key": {
"algo": "rsa",
"size": 2048
},
"names": [
{
"C": "US",
"L": "Portland",
"O": "Kubernetes",
"OU": "Kubernetes The Hard Way",
"ST": "Oregon"
}
]
}
EOF
cfssl gencert \
-ca=ca.pem \
-ca-key=ca-key.pem \
-config=ca-config.json \
-hostname=10.32.0.1,10.240.0.10,10.240.0.11,10.240.0.12,${KUBERNETES_PUBLIC_ADDRESS},127.0.0.1,${KUBERNETES_HOSTNAMES} \
-profile=kubernetes \
kubernetes-csr.json | cfssljson -bare kubernetes
The Service Account Key Pair
cat > service-account-csr.json <<EOF
{
"CN": "service-accounts",
"key": {
"algo": "rsa",
"size": 2048
},
"names": [
{
"C": "US",
"L": "Portland",
"O": "Kubernetes",
"OU": "Kubernetes The Hard Way",
"ST": "Oregon"
}
]
}
EOF
cfssl gencert \
-ca=ca.pem \
-ca-key=ca-key.pem \
-config=ca-config.json \
-profile=kubernetes \
service-account-csr.json | cfssljson -bare service-account
Distribute the Client and Server Certificates
for instance in k8s-worker-0 k8s-worker-1 k8s-worker-2; do
gcloud compute scp ca.pem ${instance}-key.pem ${instance}.pem ${instance}:~/
done
for instance in k8s-controller-0 k8s-controller-1 k8s-controller-2; do
gcloud compute scp ca.pem ca-key.pem kubernetes-key.pem kubernetes.pem \
service-account-key.pem service-account.pem ${instance}:~/
done
5. Kubernetes configuration files
KUBERNETES_PUBLIC_ADDRESS=$(gcloud compute addresses describe kubernetes-the-hard-way \
--region $(gcloud config get-value compute/region) \
--format 'value(address)')
The kubelet Kubernetes Configuration File
for instance in k8s-worker-0 k8s-worker-1 k8s-worker-2; do
kubectl config set-cluster kubernetes-the-hard-way \
--certificate-authority=ca.pem \
--embed-certs=true \
--server=https://${KUBERNETES_PUBLIC_ADDRESS}:6443 \
--kubeconfig=${instance}.kubeconfig
kubectl config set-credentials system:node:${instance} \
--client-certificate=${instance}.pem \
--client-key=${instance}-key.pem \
--embed-certs=true \
--kubeconfig=${instance}.kubeconfig
kubectl config set-context default \
--cluster=kubernetes-the-hard-way \
--user=system:node:${instance} \
--kubeconfig=${instance}.kubeconfig
kubectl config use-context default --kubeconfig=${instance}.kubeconfig
done
The kube-proxy Kubernetes Configuration File
kubectl config set-cluster kubernetes-the-hard-way \
--certificate-authority=ca.pem \
--embed-certs=true \
--server=https://${KUBERNETES_PUBLIC_ADDRESS}:6443 \
--kubeconfig=kube-proxy.kubeconfig
kubectl config set-credentials system:kube-proxy \
--client-certificate=kube-proxy.pem \
--client-key=kube-proxy-key.pem \
--embed-certs=true \
--kubeconfig=kube-proxy.kubeconfig
kubectl config set-context default \
--cluster=kubernetes-the-hard-way \
--user=system:kube-proxy \
--kubeconfig=kube-proxy.kubeconfig
kubectl config use-context default --kubeconfig=kube-proxy.kubeconfig
The kube-controller-manager Kubernetes Configuration File
kubectl config set-cluster kubernetes-the-hard-way \
--certificate-authority=ca.pem \
--embed-certs=true \
--server=https://127.0.0.1:6443 \
--kubeconfig=kube-controller-manager.kubeconfig
kubectl config set-credentials system:kube-controller-manager \
--client-certificate=kube-controller-manager.pem \
--client-key=kube-controller-manager-key.pem \
--embed-certs=true \
--kubeconfig=kube-controller-manager.kubeconfig
kubectl config set-context default \
--cluster=kubernetes-the-hard-way \
--user=system:kube-controller-manager \
--kubeconfig=kube-controller-manager.kubeconfig
kubectl config use-context default --kubeconfig=kube-controller-manager.kubeconfig
The kube-scheduler Kubernetes Configuration File
kubectl config set-cluster kubernetes-the-hard-way \
--certificate-authority=ca.pem \
--embed-certs=true \
--server=https://127.0.0.1:6443 \
--kubeconfig=kube-scheduler.kubeconfig
kubectl config set-credentials system:kube-scheduler \
--client-certificate=kube-scheduler.pem \
--client-key=kube-scheduler-key.pem \
--embed-certs=true \
--kubeconfig=kube-scheduler.kubeconfig
kubectl config set-context default \
--cluster=kubernetes-the-hard-way \
--user=system:kube-scheduler \
--kubeconfig=kube-scheduler.kubeconfig
kubectl config use-context default --kubeconfig=kube-scheduler.kubeconfig
The admin Kubernetes Configuration File
kubectl config set-cluster kubernetes-the-hard-way \
--certificate-authority=ca.pem \
--embed-certs=true \
--server=https://127.0.0.1:6443 \
--kubeconfig=admin.kubeconfig
kubectl config set-credentials admin \
--client-certificate=admin.pem \
--client-key=admin-key.pem \
--embed-certs=true \
--kubeconfig=admin.kubeconfig
kubectl config set-context default \
--cluster=kubernetes-the-hard-way \
--user=admin \
--kubeconfig=admin.kubeconfig
kubectl config use-context default --kubeconfig=admin.kubeconfig
Distribute the Kubernetes Configuration Files
for instance in k8s-worker-0 k8s-worker-1 k8s-worker-2; do
gcloud compute scp ${instance}.kubeconfig kube-proxy.kubeconfig ${instance}:~/
done
for instance in k8s-controller-0 k8s-controller-1 k8s-controller-2; do
gcloud compute scp admin.kubeconfig kube-controller-manager.kubeconfig kube-scheduler.kubeconfig ${instance}:~/
done
6. Generating the Data Encryption Config and Key
ENCRYPTION_KEY=$(head -c 32 /dev/urandom | base64)
cat > encryption-config.yaml <<EOF
kind: EncryptionConfig
apiVersion: v1
resources:
- resources:
- secrets
providers:
- aescbc:
keys:
- name: key1
secret: ${ENCRYPTION_KEY}
- identity: {}
EOF
for instance in k8s-controller-0 k8s-controller-1 k8s-controller-2; do
gcloud compute scp encryption-config.yaml ${instance}:~/
done
7. Bootstrapping the etcd Cluster
wget -q --show-progress --https-only --timestamping "https://github.com/etcd-io/etcd/releases/download/v3.4.15/etcd-v3.4.15-linux-amd64.tar.gz"
tar -xvf etcd-v3.4.15-linux-amd64.tar.gz
sudo mv etcd-v3.4.15-linux-amd64/etcd* /usr/local/bin/
sudo mkdir -p /etc/etcd /var/lib/etcd
sudo chmod 700 /var/lib/etcd
sudo cp ca.pem kubernetes-key.pem kubernetes.pem /etc/etcd/
INTERNAL_IP=$(curl -s -H "Metadata-Flavor: Google" \
http://metadata.google.internal/computeMetadata/v1/instance/network-interfaces/0/ip)
ETCD_NAME=$(hostname -s)
cat <<EOF | sudo tee /etc/systemd/system/etcd.service
[Unit]
Description=etcd
Documentation=https://github.com/coreos
[Service]
Type=notify
ExecStart=/usr/local/bin/etcd \\
--name ${ETCD_NAME} \\
--cert-file=/etc/etcd/kubernetes.pem \\
--key-file=/etc/etcd/kubernetes-key.pem \\
--peer-cert-file=/etc/etcd/kubernetes.pem \\
--peer-key-file=/etc/etcd/kubernetes-key.pem \\
--trusted-ca-file=/etc/etcd/ca.pem \\
--peer-trusted-ca-file=/etc/etcd/ca.pem \\
--peer-client-cert-auth \\
--client-cert-auth \\
--initial-advertise-peer-urls https://${INTERNAL_IP}:2380 \\
--listen-peer-urls https://${INTERNAL_IP}:2380 \\
--listen-client-urls https://${INTERNAL_IP}:2379,https://127.0.0.1:2379 \\
--advertise-client-urls https://${INTERNAL_IP}:2379 \\
--initial-cluster-token etcd-cluster-0 \\
--initial-cluster k8s-controller-0=https://10.240.0.10:2380,k8s-controller-1=https://10.240.0.11:2380,k8s-controller-2=https://10.240.0.12:2380 \\
--initial-cluster-state new \\
--data-dir=/var/lib/etcd
Restart=on-failure
RestartSec=5
[Install]
WantedBy=multi-user.target
EOF
sudo systemctl daemon-reload
sudo systemctl enable etcd
sudo systemctl start etcd
Verification
sudo ETCDCTL_API=3 etcdctl member list \
--endpoints=https://127.0.0.1:2379 \
--cacert=/etc/etcd/ca.pem \
--cert=/etc/etcd/kubernetes.pem \
--key=/etc/etcd/kubernetes-key.pem
8. Bootstrapping the Kubernetes Control Plane
Run following commands on each node of a control plane. Note that the command Default Region API doesn’t work. As a workaround, I used the command described in this GitHub issue
sudo mkdir -p /etc/kubernetes/config
wget -q --show-progress --https-only --timestamping \
"https://storage.googleapis.com/kubernetes-release/release/v1.21.0/bin/linux/amd64/kube-apiserver" \
"https://storage.googleapis.com/kubernetes-release/release/v1.21.0/bin/linux/amd64/kube-controller-manager" \
"https://storage.googleapis.com/kubernetes-release/release/v1.21.0/bin/linux/amd64/kube-scheduler" \
"https://storage.googleapis.com/kubernetes-release/release/v1.21.0/bin/linux/amd64/kubectl"
chmod +x kube-apiserver kube-controller-manager kube-scheduler kubectl
sudo mv kube-apiserver kube-controller-manager kube-scheduler kubectl /usr/local/bin/
sudo mkdir -p /var/lib/kubernetes/
sudo mv ca.pem ca-key.pem kubernetes-key.pem kubernetes.pem \
service-account-key.pem service-account.pem \
encryption-config.yaml /var/lib/kubernetes/
INTERNAL_IP=$(curl -s -H "Metadata-Flavor: Google" \
http://metadata.google.internal/computeMetadata/v1/instance/network-interfaces/0/ip)
REGION=$(curl -s -H "Metadata-Flavor: Google" http://metadata.google.internal/computeMetadata/v1/instance/zone | cut -d/ -f 4 | sed 's/.\{2\}$//')
KUBERNETES_PUBLIC_ADDRESS=$(gcloud compute addresses describe kubernetes-the-hard-way \
--region $REGION \
--format 'value(address)')
cat <<EOF | sudo tee /etc/systemd/system/kube-apiserver.service
[Unit]
Description=Kubernetes API Server
Documentation=https://github.com/kubernetes/kubernetes
[Service]
ExecStart=/usr/local/bin/kube-apiserver \\
--advertise-address=${INTERNAL_IP} \\
--allow-privileged=true \\
--apiserver-count=3 \\
--audit-log-maxage=30 \\
--audit-log-maxbackup=3 \\
--audit-log-maxsize=100 \\
--audit-log-path=/var/log/audit.log \\
--authorization-mode=Node,RBAC \\
--bind-address=0.0.0.0 \\
--client-ca-file=/var/lib/kubernetes/ca.pem \\
--enable-admission-plugins=NamespaceLifecycle,NodeRestriction,LimitRanger,ServiceAccount,DefaultStorageClass,ResourceQuota \\
--etcd-cafile=/var/lib/kubernetes/ca.pem \\
--etcd-certfile=/var/lib/kubernetes/kubernetes.pem \\
--etcd-keyfile=/var/lib/kubernetes/kubernetes-key.pem \\
--etcd-servers=https://10.240.0.10:2379,https://10.240.0.11:2379,https://10.240.0.12:2379 \\
--event-ttl=1h \\
--encryption-provider-config=/var/lib/kubernetes/encryption-config.yaml \\
--kubelet-certificate-authority=/var/lib/kubernetes/ca.pem \\
--kubelet-client-certificate=/var/lib/kubernetes/kubernetes.pem \\
--kubelet-client-key=/var/lib/kubernetes/kubernetes-key.pem \\
--runtime-config='api/all=true' \\
--service-account-key-file=/var/lib/kubernetes/service-account.pem \\
--service-account-signing-key-file=/var/lib/kubernetes/service-account-key.pem \\
--service-account-issuer=https://${KUBERNETES_PUBLIC_ADDRESS}:6443 \\
--service-cluster-ip-range=10.32.0.0/24 \\
--service-node-port-range=30000-32767 \\
--tls-cert-file=/var/lib/kubernetes/kubernetes.pem \\
--tls-private-key-file=/var/lib/kubernetes/kubernetes-key.pem \\
--v=2
Restart=on-failure
RestartSec=5
[Install]
WantedBy=multi-user.target
EOF
sudo mv kube-controller-manager.kubeconfig /var/lib/kubernetes/
cat <<EOF | sudo tee /etc/systemd/system/kube-controller-manager.service
[Unit]
Description=Kubernetes Controller Manager
Documentation=https://github.com/kubernetes/kubernetes
[Service]
ExecStart=/usr/local/bin/kube-controller-manager \\
--bind-address=0.0.0.0 \\
--cluster-cidr=10.200.0.0/16 \\
--cluster-name=kubernetes \\
--cluster-signing-cert-file=/var/lib/kubernetes/ca.pem \\
--cluster-signing-key-file=/var/lib/kubernetes/ca-key.pem \\
--kubeconfig=/var/lib/kubernetes/kube-controller-manager.kubeconfig \\
--leader-elect=true \\
--root-ca-file=/var/lib/kubernetes/ca.pem \\
--service-account-private-key-file=/var/lib/kubernetes/service-account-key.pem \\
--service-cluster-ip-range=10.32.0.0/24 \\
--use-service-account-credentials=true \\
--v=2
Restart=on-failure
RestartSec=5
[Install]
WantedBy=multi-user.target
EOF
sudo mv kube-scheduler.kubeconfig /var/lib/kubernetes/
cat <<EOF | sudo tee /etc/kubernetes/config/kube-scheduler.yaml
apiVersion: kubescheduler.config.k8s.io/v1beta1
kind: KubeSchedulerConfiguration
clientConnection:
kubeconfig: "/var/lib/kubernetes/kube-scheduler.kubeconfig"
leaderElection:
leaderElect: true
EOF
cat <<EOF | sudo tee /etc/systemd/system/kube-scheduler.service
[Unit]
Description=Kubernetes Scheduler
Documentation=https://github.com/kubernetes/kubernetes
[Service]
ExecStart=/usr/local/bin/kube-scheduler \\
--config=/etc/kubernetes/config/kube-scheduler.yaml \\
--v=2
Restart=on-failure
RestartSec=5
[Install]
WantedBy=multi-user.target
EOF
sudo systemctl daemon-reload
sudo systemctl enable kube-apiserver kube-controller-manager kube-scheduler
sudo systemctl start kube-apiserver kube-controller-manager kube-scheduler
Enable HTTP Check
sudo apt-get update
sudo apt-get install -y nginx
cat > kubernetes.default.svc.cluster.local <<EOF
server {
listen 80;
server_name kubernetes.default.svc.cluster.local;
location /healthz {
proxy_pass https://127.0.0.1:6443/healthz;
proxy_ssl_trusted_certificate /var/lib/kubernetes/ca.pem;
}
}
EOF
sudo mv kubernetes.default.svc.cluster.local /etc/nginx/sites-available/kubernetes.default.svc.cluster.local
sudo ln -s /etc/nginx/sites-available/kubernetes.default.svc.cluster.local /etc/nginx/sites-enabled/
sudo systemctl restart nginx
sudo systemctl enable nginx
Verification
kubectl cluster-info --kubeconfig admin.kubeconfig
curl -H "Host: kubernetes.default.svc.cluster.local" -i http://127.0.0.1/healthz
Kubernetes Cluster configuration
RBAC
cat <<EOF | kubectl apply --kubeconfig admin.kubeconfig -f -
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
annotations:
rbac.authorization.kubernetes.io/autoupdate: "true"
labels:
kubernetes.io/bootstrapping: rbac-defaults
name: system:kube-apiserver-to-kubelet
rules:
- apiGroups:
- ""
resources:
- nodes/proxy
- nodes/stats
- nodes/log
- nodes/spec
- nodes/metrics
verbs:
- "*"
EOF
cat <<EOF | kubectl apply --kubeconfig admin.kubeconfig -f -
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
name: system:kube-apiserver
namespace: ""
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: system:kube-apiserver-to-kubelet
subjects:
- apiGroup: rbac.authorization.k8s.io
kind: User
name: kubernetes
EOF
Front Load Balancer
KUBERNETES_PUBLIC_ADDRESS=$(gcloud compute addresses describe kubernetes-the-hard-way \
--region $(gcloud config get-value compute/region) \
--format 'value(address)')
gcloud compute http-health-checks create kubernetes \
--description "Kubernetes Health Check" \
--host "kubernetes.default.svc.cluster.local" \
--request-path "/healthz"
gcloud compute firewall-rules create kubernetes-the-hard-way-allow-health-check \
--network kubernetes-the-hard-way \
--source-ranges 209.85.152.0/22,209.85.204.0/22,35.191.0.0/16 \
--allow tcp
gcloud compute target-pools create kubernetes-target-pool \
--http-health-check kubernetes
gcloud compute target-pools add-instances kubernetes-target-pool \
--instances k8s-controller-0,k8s-controller-1,k8s-controller-2
gcloud compute forwarding-rules create kubernetes-forwarding-rule \
--address ${KUBERNETES_PUBLIC_ADDRESS} \
--ports 6443 \
--region $(gcloud config get-value compute/region) \
--target-pool kubernetes-target-pool
Verification
KUBERNETES_PUBLIC_ADDRESS=$(gcloud compute addresses describe kubernetes-the-hard-way \
--region $(gcloud config get-value compute/region) \
--format 'value(address)')
curl --cacert ca.pem https://${KUBERNETES_PUBLIC_ADDRESS}:6443/version
9. Bootstrapping the Kubernetes Worker Nodes
Provision a worker node
sudo apt-get update
sudo apt-get -y install socat conntrack ipset
wget -q --show-progress --https-only --timestamping \
https://github.com/kubernetes-sigs/cri-tools/releases/download/v1.21.0/crictl-v1.21.0-linux-amd64.tar.gz \
https://github.com/opencontainers/runc/releases/download/v1.0.0-rc93/runc.amd64 \
https://github.com/containernetworking/plugins/releases/download/v0.9.1/cni-plugins-linux-amd64-v0.9.1.tgz \
https://github.com/containerd/containerd/releases/download/v1.4.4/containerd-1.4.4-linux-amd64.tar.gz \
https://storage.googleapis.com/kubernetes-release/release/v1.21.0/bin/linux/amd64/kubectl \
https://storage.googleapis.com/kubernetes-release/release/v1.21.0/bin/linux/amd64/kube-proxy \
https://storage.googleapis.com/kubernetes-release/release/v1.21.0/bin/linux/amd64/kubelet
sudo mkdir -p \
/etc/cni/net.d \
/opt/cni/bin \
/var/lib/kubelet \
/var/lib/kube-proxy \
/var/lib/kubernetes \
/var/run/kubernetes
mkdir containerd
tar -xvf crictl-v1.21.0-linux-amd64.tar.gz
tar -xvf containerd-1.4.4-linux-amd64.tar.gz -C containerd
sudo tar -xvf cni-plugins-linux-amd64-v0.9.1.tgz -C /opt/cni/bin/
sudo mv runc.amd64 runc
chmod +x crictl kubectl kube-proxy kubelet runc
sudo mv crictl kubectl kube-proxy kubelet runc /usr/local/bin/
sudo mv containerd/bin/* /bin/
Configure CNI Networking
- IPAM: IP Address Allocation
- ipMasq: Set up IP masquarade. This is necessary if the host will act as a gateway to subnets that are not able to route to the IP assigned to the container
POD_CIDR=$(curl -s -H "Metadata-Flavor: Google" \
http://metadata.google.internal/computeMetadata/v1/instance/attributes/pod-cidr)
cat <<EOF | sudo tee /etc/cni/net.d/10-bridge.conf
{
"cniVersion": "0.4.0",
"name": "bridge",
"type": "bridge",
"bridge": "cnio0",
"isGateway": true,
"ipMasq": true,
"ipam": {
"type": "host-local",
"ranges": [
[{"subnet": "${POD_CIDR}"}]
],
"routes": [{"dst": "0.0.0.0/0"}]
}
}
EOF
cat <<EOF | sudo tee /etc/cni/net.d/99-loopback.conf
{
"cniVersion": "0.4.0",
"name": "lo",
"type": "loopback"
}
EOF
Containerd
sudo mkdir -p /etc/containerd/
cat << EOF | sudo tee /etc/containerd/config.toml
[plugins]
[plugins.cri.containerd]
snapshotter = "overlayfs"
[plugins.cri.containerd.default_runtime]
runtime_type = "io.containerd.runtime.v1.linux"
runtime_engine = "/usr/local/bin/runc"
runtime_root = ""
EOF
cat <<EOF | sudo tee /etc/systemd/system/containerd.service
[Unit]
Description=containerd container runtime
Documentation=https://containerd.io
After=network.target
[Service]
ExecStartPre=/sbin/modprobe overlay
ExecStart=/bin/containerd
Restart=always
RestartSec=5
Delegate=yes
KillMode=process
OOMScoreAdjust=-999
LimitNOFILE=1048576
LimitNPROC=infinity
LimitCORE=infinity
[Install]
WantedBy=multi-user.target
EOF
Configure Kubelet
sudo mv ${HOSTNAME}-key.pem ${HOSTNAME}.pem /var/lib/kubelet/
sudo mv ${HOSTNAME}.kubeconfig /var/lib/kubelet/kubeconfig
sudo mv ca.pem /var/lib/kubernetes/
cat <<EOF | sudo tee /var/lib/kubelet/kubelet-config.yaml
kind: KubeletConfiguration
apiVersion: kubelet.config.k8s.io/v1beta1
authentication:
anonymous:
enabled: false
webhook:
enabled: true
x509:
clientCAFile: "/var/lib/kubernetes/ca.pem"
authorization:
mode: Webhook
clusterDomain: "cluster.local"
clusterDNS:
- "10.32.0.10"
podCIDR: "${POD_CIDR}"
resolvConf: "/run/systemd/resolve/resolv.conf"
runtimeRequestTimeout: "15m"
tlsCertFile: "/var/lib/kubelet/${HOSTNAME}.pem"
tlsPrivateKeyFile: "/var/lib/kubelet/${HOSTNAME}-key.pem"
EOF
cat <<EOF | sudo tee /etc/systemd/system/kubelet.service
[Unit]
Description=Kubernetes Kubelet
Documentation=https://github.com/kubernetes/kubernetes
After=containerd.service
Requires=containerd.service
[Service]
ExecStart=/usr/local/bin/kubelet \\
--config=/var/lib/kubelet/kubelet-config.yaml \\
--container-runtime=remote \\
--container-runtime-endpoint=unix:///var/run/containerd/containerd.sock \\
--image-pull-progress-deadline=2m \\
--kubeconfig=/var/lib/kubelet/kubeconfig \\
--network-plugin=cni \\
--register-node=true \\
--v=2
Restart=on-failure
RestartSec=5
[Install]
WantedBy=multi-user.target
EOF
Configure the Kube Proxy
sudo mv kube-proxy.kubeconfig /var/lib/kube-proxy/kubeconfig
cat <<EOF | sudo tee /var/lib/kube-proxy/kube-proxy-config.yaml
kind: KubeProxyConfiguration
apiVersion: kubeproxy.config.k8s.io/v1alpha1
clientConnection:
kubeconfig: "/var/lib/kube-proxy/kubeconfig"
mode: "iptables"
clusterCIDR: "10.200.0.0/16"
EOF
cat <<EOF | sudo tee /etc/systemd/system/kube-proxy.service
[Unit]
Description=Kubernetes Kube Proxy
Documentation=https://github.com/kubernetes/kubernetes
[Service]
ExecStart=/usr/local/bin/kube-proxy \\
--config=/var/lib/kube-proxy/kube-proxy-config.yaml
Restart=on-failure
RestartSec=5
[Install]
WantedBy=multi-user.target
EOF
Start daemons
sudo systemctl daemon-reload
sudo systemctl enable containerd kubelet kube-proxy
sudo systemctl start containerd kubelet kube-proxy
Confirmation
$ kubectl get nodes --kubeconfig admin.kubeconfig
10. Configuring kubectl for Remote Access
kubectl
KUBERNETES_PUBLIC_ADDRESS=$(gcloud compute addresses describe kubernetes-the-hard-way \
--region $(gcloud config get-value compute/region) \
--format 'value(address)')
kubectl config set-cluster kubernetes-the-hard-way \
--certificate-authority=ca.pem \
--embed-certs=true \
--server=https://${KUBERNETES_PUBLIC_ADDRESS}:6443
kubectl config set-credentials admin \
--client-certificate=admin.pem \
--client-key=admin-key.pem
kubectl config set-context kubernetes-the-hard-way \
--cluster=kubernetes-the-hard-way \
--user=admin
kubectl config use-context kubernetes-the-hard-way
11. Provisioning Pod Network Routes
for instance in k8s-worker-0 k8s-worker-1 k8s-worker-2; do
gcloud compute instances describe ${instance} \
--format 'value[separator=" "](networkInterfaces[0].networkIP,metadata.items[0].value)'
done
for i in 0 1 2; do
gcloud compute routes create kubernetes-route-10-200-${i}-0-24 \
--network kubernetes-the-hard-way \
--next-hop-address 10.240.0.2${i} \
--destination-range 10.200.${i}.0/24
done
Confirmation.
gcloud compute routes list --filter "network: kubernetes-the-hard-way"
12. Deploying the DNS Cluster Add-on
There is no core dns 1.8 file anymore. So, following this GitHub comment, I downloaded CoreDNS 1.7 committed in the repository originally.
kubectl apply -f https://raw.githubusercontent.com/kelseyhightower/kubernetes-the-hard-way/master/deployments/coredns-1.7.0.yaml
Confirm application
bash-5.2$ kubectl get pods -l k8s-app=kube-dns -n kube-system
NAME READY STATUS RESTARTS AGE
coredns-748f75f5fb-wqqcb 1/1 Running 0 13s
coredns-748f75f5fb-wqr9m 1/1 Running 0 13s
Verification
kubectl get pods -l run=busybox
POD_NAME=$(kubectl get pods -l run=busybox -o jsonpath="{.items[0].metadata.name}")
kubectl exec -ti $POD_NAME -- nslookup kubernetes
Output was
Server: 10.32.0.10
Address 1: 10.32.0.10 kube-dns.kube-system.svc.cluster.local
Name: kubernetes
Address 1: 10.32.0.1 kubernetes.default.svc.cluster.local
These IPs came from services
bash-5.2$ kubectl get svc -n kube-system -o wide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
kube-dns ClusterIP 10.32.0.10 <none> 53/UDP,53/TCP,9153/TCP 9m32s k8s-app=kube-dns
bash-5.2$ kubectl get svc -owide
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
kubernetes ClusterIP 10.32.0.1 <none> 443/TCP 14d <none>
bash-5.2$ kubectl get svc -o yaml kubernetes
apiVersion: v1
kind: Service
metadata:
creationTimestamp: "2023-07-16T04:03:32Z"
labels:
component: apiserver
provider: kubernetes
name: kubernetes
namespace: default
resourceVersion: "208"
uid: a0b09bfc-5464-4ddc-ab21-3787ac9dec44
spec:
clusterIP: 10.32.0.1
clusterIPs:
- 10.32.0.1
ipFamilies:
- IPv4
ipFamilyPolicy: SingleStack
ports:
- name: https
port: 443
protocol: TCP
targetPort: 6443
sessionAffinity: None
type: ClusterIP
status:
loadBalancer: {}
I couldn’t find where this service is defined. Maybe kube-proxy or kubelet configurations included it.
13. Smoke Test
Secret
kubectl create secret generic kubernetes-the-hard-way \
--from-literal="mykey=mydata"
gcloud compute ssh k8s-controller-0 \
--command "sudo ETCDCTL_API=3 etcdctl get \
--endpoints=https://127.0.0.1:2379 \
--cacert=/etc/etcd/ca.pem \
--cert=/etc/etcd/kubernetes.pem \
--key=/etc/etcd/kubernetes-key.pem\
/registry/secrets/default/kubernetes-the-hard-way | hexdump -C"
etcd
Just looking around etcd data.
- Checking keys stored in etcd following this comment
$ sudo ETCDCTL_API=3 etcdctl --endpoints=https://127.0.0.1:2379 --cacert=/etc/etcd/ca.pem --cert=/etc/etcd/kubernetes.pem --key=/etc/etcd/kubernetes-key.pem get / --prefix --keys-only | head -n 5
/registry/apiregistration.k8s.io/apiservices/v1.
/registry/apiregistration.k8s.io/apiservices/v1.admissionregistration.k8s.io
/registry/apiregistration.k8s.io/apiservices/v1.apiextensions.k8s.io
Get a revision of a key
$ sudo ETCDCTL_API=3 etcdctl --endpoints=https://127.0.0.1:2379 --cacert=/etc/etcd/ca.pem --cert=/etc/etcd/kubernetes.pem --key=/etc/etcd/kubernetes-key.pem get /registry/deployments/kube-system/coredns -w json | jq .
{
"header": {
"cluster_id": 4502693191618639400,
"member_id": 17982242243123227000,
"revision": 2046681,
"raft_term": 123
},
"kvs": [
{
"key": "L3JlZ2lzdHJ5L2RlcGxveW1lbnRzL2t1YmUtc3lzdGVtL2NvcmVkbnM=",
"create_revision": 2041628,
"mod_revision": 2041695,
"version": 6,
"value": "<BASE 64 ENCODED>"
}
],
"count": 1
}
Deployment
kubectl create deployment nginx --image=nginx
POD_NAME=$(kubectl get pods -l app=nginx -o jsonpath="{.items[0].metadata.name}")
Port forwarding
$ kubectl port-forward $POD_NAME 8080:80
$ curl --head http://127.0.0.1:8080
HTTP/1.1 200 OK
Server: nginx/1.25.1
Date: Sun, 30 Jul 2023 23:38:57 GMT
Content-Type: text/html
Content-Length: 615
Last-Modified: Tue, 13 Jun 2023 15:08:10 GMT
Connection: keep-alive
ETag: "6488865a-267"
Accept-Ranges: bytes
Logs
$ kubectl logs $POD_NAME
/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration
/docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/
/docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh
10-listen-on-ipv6-by-default.sh: info: Getting the checksum of /etc/nginx/conf.d/default.conf
10-listen-on-ipv6-by-default.sh: info: Enabled listen on IPv6 in /etc/nginx/conf.d/default.conf
/docker-entrypoint.sh: Sourcing /docker-entrypoint.d/15-local-resolvers.envsh
/docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh
/docker-entrypoint.sh: Launching /docker-entrypoint.d/30-tune-worker-processes.sh
/docker-entrypoint.sh: Configuration complete; ready for start up
2023/07/30 23:36:31 [notice] 1#1: using the "epoll" event method
2023/07/30 23:36:31 [notice] 1#1: nginx/1.25.1
2023/07/30 23:36:31 [notice] 1#1: built by gcc 12.2.0 (Debian 12.2.0-14)
2023/07/30 23:36:31 [notice] 1#1: OS: Linux 5.15.0-1036-gcp
2023/07/30 23:36:31 [notice] 1#1: getrlimit(RLIMIT_NOFILE): 1048576:1048576
2023/07/30 23:36:31 [notice] 1#1: start worker processes
2023/07/30 23:36:31 [notice] 1#1: start worker process 28
2023/07/30 23:36:31 [notice] 1#1: start worker process 29
127.0.0.1 - - [30/Jul/2023:23:38:47 +0000] "GET / HTTP/1.1" 200 615 "-" "curl/7.88.1" "-"
127.0.0.1 - - [30/Jul/2023:23:38:50 +0000] "GET / HTTP/1.1" 200 615 "-" "curl/7.88.1" "-"
127.0.0.1 - - [30/Jul/2023:23:38:57 +0000] "HEAD / HTTP/1.1" 200 0 "-" "curl/7.88.1" "-"
Exec
$ kubectl exec -ti $POD_NAME -- nginx -v
nginx version: nginx/1.25.1
Services
kubectl expose deployment nginx --port 80 --type NodePort
NODE_PORT=$(kubectl get svc nginx \
--output=jsonpath='{range .spec.ports[0]}{.nodePort}')
gcloud compute firewall-rules create kubernetes-the-hard-way-allow-nginx-service \
--allow=tcp:${NODE_PORT} \
--network kubernetes-the-hard-way
Confirmation
EXTERNAL_IP=$(gcloud compute instances describe k8s-worker-0 \
--format 'value(networkInterfaces[0].accessConfigs[0].natIP)')
curl -I http://${EXTERNAL_IP}:${NODE_PORT}
14. Cleaning Up
Following steps haven’t been tested yet.
gcloud -q compute instances delete \
k8s-controller-0 k8s-controller-1 k8s-controller-2 \
k8s-worker-0 k8s-worker-1 k8s-worker-2 \
--zone $(gcloud config get-value compute/zone)
gcloud -q compute forwarding-rules delete kubernetes-forwarding-rule \
--region $(gcloud config get-value compute/region)
gcloud -q compute target-pools delete kubernetes-target-pool
gcloud -q compute http-health-checks delete kubernetes
gcloud -q compute addresses delete kubernetes-the-hard-way
gcloud -q compute firewall-rules delete \
kubernetes-the-hard-way-allow-nginx-service \
kubernetes-the-hard-way-allow-internal \
kubernetes-the-hard-way-allow-external \
kubernetes-the-hard-way-allow-health-check
gcloud -q compute routes delete \
kubernetes-route-10-200-0-0-24 \
kubernetes-route-10-200-1-0-24 \
kubernetes-route-10-200-2-0-24
gcloud -q compute networks subnets delete kubernetes
gcloud -q compute networks delete kubernetes-the-hard-way
gcloud -q compute addresses delete kubernetes-the-hard-way \
--region $(gcloud config get-value compute/region)