kelseyhightower Kubernetes The Hard Way


CFSSL consists of:
  • a set of packages useful for building custom TLS PKI tools
  • the cfssl program, which is the canonical command line utility using the CFSSL packages.
  • the multirootca program, which is a certificate authority server that can use multiple signing keys.
  • the mkbundle program is used to build certificate pool bundles.
  • the cfssljson program, which takes the JSON output from the cfssl and multirootca programs and writes certificates, keys, CSRs, and bundles to disk.
The cfssl command line tool takes a command to specify what operation it should carry out:
   sign             signs a certificate
   bundle           build a certificate bundle
   genkey           generate a private key and a certificate request
   gencert          generate a private key and a certificate
   serve            start the API server
   version          prints out the current version
   selfsign         generates a self-signed certificate
   print-defaults   print default configurations
Use cfssl [command] -help to find out more about a command. The version command takes no arguments.
Networking
gcloud compute networks : kubernetes-the-hard-way
gcloud compute networks subnets : 10.240.0.0/24
gcloud compute firewall-rules
1. tcp, udp, icmp : source-ranges 10.240.0.0/24,10.200.0.0/16
2. tcp:22,tcp:6443,icmp : source-ranges 0.0.0.0/0
gcloud compute firewall-rules list
Now, create public address
gcloud compute addresses
Compute
3 K8s controllers: 
controller-0: 10.240.0.10
controller-1: 10.240.0.11
controller-2: 10.240.0.12
POD CIDR : 10.200.0.0/16
3 Worker node
worker-0: 10.240.0.20 pod-cidr 10.200.0.0/24
worker-1: 10.240.0.21 pod-cidr 10.200.1.0/24
worker-2: 10.240.0.22 pod-cidr 10.200.2.0/24
TLS Certificates
TLS certificates for the following components: 
* etcd, 
* kube-apiserver, 
* kube-controller-manager, 
* kube-scheduler, 
* kubelet, and 
* kube-proxy.
A public key infrastructure (PKI) is a set of roles, policies, hardware, software and procedures needed to create, manage, distribute, use, store and revoke digital certificates and manage public-key encryption. In cryptography, a PKI is an arrangement that binds public keys with respective identities of entities (like people and organizations).
Generate
1. ca.config file
Usage: 
"signing", 
"key encipherment", 
"server auth", 
"client auth"
2. Generate CSR JSON file
Output: Private key and Certificate for CA
3. Generate various CSR JSON files. Use CA key, CA key certificate, CA config file. 
Output Private key and Certificate 
3.1. Admin
3.2. for each worker node for kubelet. 
3.3  for kube-controller-manager
3.4 kube-proxy
3.5 kube-scheduler
4. Generate K8s API server certificate. 
For -hostname argument pass
KUBERNETES_HOSTNAMES=kubernetes,kubernetes.default,kubernetes.default.svc,kubernetes.default.svc.cluster,kubernetes.svc.cluster.local, K8s master node public IP, K8s all master nodes' private IP addresses. 
5. Generate Service Account pair
scp
6. To Worker node copy (scp) the following files
ca.pem
worker-N-key.pem
worker-N.pem
7. To all master node, copy (scp) following files
ca.pem
ca-key.pm
kubernetes.pm
kubernetes-key.pm
service-account.pm
service-account-key.pm
client authentication configuration
The kube-proxy, kube-controller-manager, kube-scheduler, and kubelet client certificates will be used to generate client authentication configuration file, also known as kubeconfigs. It enables Kubernetes clients to locate and authenticate to the Kubernetes API Servers.
Node authorization is a special-purpose authorization mode that specifically authorizes API requests made by kubelets. https://kubernetes.io/docs/reference/access-authn-authz/node/
1. Generate kubeconfig file for each worker node, with user name as system:node:workerN. The output is worker-N.kubeconfig
2. Generate kubeconfig file for the kube-proxy service. The output is kube-proxy.kubeconfig
3. Generate a kubeconfig file for the kube-controller-manager service. here server is 127.0.0.1 and output is kube-controller-manager.kubeconfig
4. Generate a kubeconfig file for the kube-scheduler service. here server is 127.0.0.1 and output is kube-scheduler.kubeconfig
5. Generate a kubeconfig file for the admin user. here server is 127.0.0.1 and output is admin.kubeconfig
To generate .kubeconfig file, we will use these three commands:
kubectl config set-cluster
kubectl config set-credentials
kubectl config set-context
Files for worker nodes:
  • worker-N.kubeconfig
  • kube-proxy.kubeconfig

Files for master nodes
  • admin.kubeconfig 
  • kube-controller-manager.kubeconfig 
  • kube-scheduler.kubeconfig

Data Encryption Config and Key
1. Generate encryption key with command
head -c 32 /dev/urandom | base64
2. Generate encryption-config.yaml file using that encryption key. 
Upload it on all three master node. 
Bootstrap etcd
On each master node
1. download and install etcd
2. copy these 3 files at /etc/etcd
ca.pem 
kubernetes-key.pem 
kubernetes.pem
3. Create /etc/systemd/system/etcd.service file. It opesn 2379 and 2380 port for etcd
4. Start etcd service
Bootstrap k8s-controller, K8s API server, K8s Scheduler 
On each master node
1. download and install 
kube-apiserver
kube-controller-manager
kube-scheduler
kubectl
2. Move all binary to /usr/local/bin
3. Move the following files to /var/lib/kubernetes/
ca.pem ca-key.pem kubernetes-key.pem kubernetes.pem service-account-key.pem service-account.pem   encryption-config.yaml
kube-controller-manager.kubeconfig
kube-scheduler.kubeconfig 
4. Create .service file for each of them at /etc/systemd/system/
For API server specify etcd and other parameters
  --service-cluster-ip-range=10.32.0.0/24 \\
  --service-node-port-range=30000-32767 \\
We can configure nginx for healthcheck of any service. Copy kubernetes.default.svc.cluster.local file at /etc/nginx/sites-available/
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;
  }
}
RBAC for Kubelet Authorization
Let's set the Kubelet --authorization-mode flag to Webhook. Webhook mode uses the SubjectAccessReview API to determine authorization.
1. Create the system:kube-apiserver-to-kubelet ClusterRole with permissions to access the Kubelet API and perform most common tasks associated with managing pods:
2. Bind the system:kube-apiserver-to-kubelet ClusterRole to the kubernetes user:
It is sufficient to run on any one worker with kubectl
K8s Frontend LoadBalancer
Bootstrapping the Kubernetes Worker Nodes
1. First install
socat conntrack ipset
The socat binary enables support for the kubectl port-forward command.
2. Turn off swap
sudo swapoff -a
3. download and install 
critools (cri-ctl)
runc, container networking plugins, containerd, kubelet, and kube-proxy.
4. Installation directory 
  /etc/cni/net.d \
  /opt/cni/bin \
  /var/lib/kubelet \
  /var/lib/kube-proxy \
  /var/lib/kubernetes \
  /var/run/kubernetes
5. Create network configuration file at /etc/cni/net.d/
10-bridge.conf
99-loopback.conf
6. configure containerd service
7. configure Kubelet
8. configure kube-proxy
9. Start services: containerd kubelet kube-proxy
Configuring kubectl for Remote Access
Use the following commands
kubectl config set-cluster  // --certificate-authority=ca.pem
kubectl config set-credentials // --client-certificate=admin.pem  --client-key=admin-key.pem
kubectl config set-context // --user=admin
kubectl config use-context 
Provisioning Pod Network Routes
Add route for pods CIDR on each node, with destination as node's IP address. 
Deploying the DNS Cluster Add-on
https://storage.googleapis.com/kubernetes-the-hard-way/coredns.yaml

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