In this lab you will bootstrap the Kubernetes control plane across three compute instances and configure it for high availability. You will also create an external load balancer that exposes the Kubernetes API Servers to remote clients. The following components will be installed on each node: Kubernetes API Server, Scheduler, and Controller Manager.
The commands in this lab must be run on each controller instance: controller-0
, controller-1
, and controller-2
. Login to each controller instance:
ssh controller-0.${DOMAIN}
tmux can be used to run commands on multiple compute instances at the same time. See the Running commands in parallel with tmux section in the Prerequisites lab.
Create the Kubernetes configuration directory:
sudo mkdir -p /etc/kubernetes/config
Download the official Kubernetes release binaries:
wget -q --timestamping \
"https://storage.googleapis.com/kubernetes-release/release/v1.15.3/bin/linux/amd64/kube-apiserver" \
"https://storage.googleapis.com/kubernetes-release/release/v1.15.3/bin/linux/amd64/kube-controller-manager" \
"https://storage.googleapis.com/kubernetes-release/release/v1.15.3/bin/linux/amd64/kube-scheduler" \
"https://storage.googleapis.com/kubernetes-release/release/v1.15.3/bin/linux/amd64/kubectl"
Install the Kubernetes binaries:
{
chmod +x kube-apiserver kube-controller-manager kube-scheduler kubectl
sudo mv kube-apiserver kube-controller-manager kube-scheduler kubectl /usr/local/bin/
}
{
sudo mkdir -p /var/lib/kubernetes/
sudo mv ca.pem ca-key.pem kubernetes-key.pem kubernetes.pem \
service-account-key.pem service-account.pem \
encryption-config.yaml /var/lib/kubernetes/
}
The instance internal IP address will be used to advertise the API Server to members of the cluster. Retrieve the internal IP address for the current compute instance:
INTERNAL_IP=$(curl -s http://169.254.169.254/latest/meta-data/local-ipv4)
Create the kube-apiserver.service
systemd unit file:
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 \\
--kubelet-https=true \\
--runtime-config=api/all \\
--service-account-key-file=/var/lib/kubernetes/service-account.pem \\
--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
Move the kube-controller-manager
kubeconfig into place:
sudo mv kube-controller-manager.kubeconfig /var/lib/kubernetes/
Each worker instance requires a pod subnet allocation from the Kubernetes cluster CIDR range. The pod subnet allocation will be used to configure container networking by kube-route
in a later exercise.
The Kubernetes cluster CIDR range is defined by the Controller Manager's
--cluster-cidr
flag. In this tutorial the cluster CIDR range will be set to10.200.0.0/16
, which supports 254 subnets.
The Controller Manager allocate pod subnet by the cluster CIDR range definition if the
--allocate-node-cidrs
flag is enabled.
Create the kube-controller-manager.service
systemd unit file:
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 \\
--address=0.0.0.0 \\
--allocate-node-cidrs=true \\
--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
Move the kube-scheduler
kubeconfig into place:
sudo mv kube-scheduler.kubeconfig /var/lib/kubernetes/
Create the kube-scheduler.yaml
configuration file:
cat <<EOF | sudo tee /etc/kubernetes/config/kube-scheduler.yaml
apiVersion: kubescheduler.config.k8s.io/v1alpha1
kind: KubeSchedulerConfiguration
clientConnection:
kubeconfig: "/var/lib/kubernetes/kube-scheduler.kubeconfig"
leaderElection:
leaderElect: true
EOF
Create the kube-scheduler.service
systemd unit file:
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 --now
}
Allow up to 10 seconds for the Kubernetes API Server to fully initialize.
kubectl get componentstatuses --kubeconfig admin.kubeconfig
NAME STATUS MESSAGE ERROR
controller-manager Healthy ok
scheduler Healthy ok
etcd-2 Healthy {"health": "true"}
etcd-0 Healthy {"health": "true"}
etcd-1 Healthy {"health": "true"}
Disable selinux (I know, I know):
sudo sed -i -e 's/^SELINUX=enforcing$/SELINUX=disabled/' /etc/selinux/config
Update to the latest version of all the packages and reboot the instances just in case:
{
sudo yum update -y
sudo reboot
}
In this section you will configure RBAC permissions to allow the Kubernetes API Server to access the Kubelet API on each worker node. Access to the Kubelet API is required for retrieving metrics, logs, and executing commands in pods.
This tutorial sets the Kubelet
--authorization-mode
flag toWebhook
. Webhook mode uses the SubjectAccessReview API to determine authorization.
The commands in this section will effect the entire cluster and only need to be run once from one of the controller nodes.
ssh controller-0.${DOMAIN}
Create the system:kube-apiserver-to-kubelet
ClusterRole with permissions to access the Kubelet API and perform most common tasks associated with managing pods:
cat <<EOF | kubectl apply --kubeconfig admin.kubeconfig -f -
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
annotations:
rbac.authorization.kubernetes.io/autoupdate: "true"
labels:
kubernetes.io/bootstrapping: rbac-defaults
name: system:kube-apiserver-to-kubelet
rules:
- apiGroups:
- ""
resources:
- nodes/proxy
- nodes/stats
- nodes/log
- nodes/spec
- nodes/metrics
verbs:
- "*"
EOF
The Kubernetes API Server authenticates to the Kubelet as the kubernetes
user using the client certificate as defined by the --kubelet-client-certificate
flag.
Bind the system:kube-apiserver-to-kubelet
ClusterRole to the kubernetes
user:
cat <<EOF | kubectl apply --kubeconfig admin.kubeconfig -f -
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRoleBinding
metadata:
name: system:kube-apiserver
namespace: ""
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: system:kube-apiserver-to-kubelet
subjects:
- apiGroup: rbac.authorization.k8s.io
kind: User
name: kubernetes
EOF
Retrieve the kubernetes-the-hard-way
static IP address:
KUBERNETES_PUBLIC_ADDRESS=$(openstack server show k8sosp.${DOMAIN} -f json -c addresses | jq -r '.["addresses"]["kubernetes-the-hard-way"]|last')
Make a HTTP request for the Kubernetes version info:
curl --cacert ca.pem https://${KUBERNETES_PUBLIC_ADDRESS}:6443/version
output
{
"major": "1",
"minor": "15",
"gitVersion": "v1.15.3",
"gitCommit": "2d3c76f9091b6bec110a5e63777c332469e0cba2",
"gitTreeState": "clean",
"buildDate": "2019-08-19T11:05:50Z",
"goVersion": "go1.12.9",
"compiler": "gc",
"platform": "linux/amd64"
}