kubeadm

ben.wangzAbout 2 min

kubeadm

references

https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/
https://docs.fedoraproject.org/en-US/quick-docs/using-kubernetes/

prepare

1 node with fedora 38(use fedora 39 if you are play with aliyun ecs)
root account required

install necessary packages for each node

```
dnf -y install iptables iproute-tc
```

enable cri-o repo

for-fedora-38

dnf -y module enable cri-o:${KUBE_VERSION}

for rhel-8

KUBE_VERSION=1.28
cat <<EOF | tee /etc/yum.repos.d/cri-o.repo
[cri-o]
name=CRI-O
baseurl=https://pkgs.k8s.io/addons:/cri-o:/stable:/v${KUBE_VERSION}/rpm/
enabled=1
gpgcheck=1
gpgkey=https://pkgs.k8s.io/addons:/cri-o:/stable:/v${KUBE_VERSION}/rpm/repodata/repomd.xml.key
EOF

enable kubernetes repo

KUBE_VERSION=1.28
cat <<EOF | sudo tee /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://pkgs.k8s.io/core:/stable:/v${KUBE_VERSION}/rpm/
enabled=1
gpgcheck=1
gpgkey=https://pkgs.k8s.io/core:/stable:/v${KUBE_VERSION}/rpm/repodata/repomd.xml.key
exclude=kubelet kubeadm kubectl cri-tools kubernetes-cni
EOF

install components

dnf -y install cri-o kubeadm kubelet kubectl --disableexcludes=kubernetes

configure node

change hostname of master node
- ```
hostnamectl set-hostname k8s-master
```

configure /etc/hosts

# change ip according to your own machine
cat >> /etc/hosts <<EOF
192.168.1.109 k8s-master
EOF

configure ntp

dnf install -y chrony \
    && systemctl enable chronyd \
    && systemctl start chronyd \
    && chronyc sources \
    && chronyc tracking \
    && timedatectl set-timezone 'Asia/Shanghai'

turn off selinux, firewalld and swap of each node

sed -i 's/^SELINUX=.*/SELINUX=disabled/' /etc/selinux/config && setenforce 0

systemctl stop firewalld && systemctl disable firewalld

systemctl stop swap-create@zram0
dnf remove -y zram-generator-defaults
swapoff -a

configure forwarding IPv4

cat <<EOF | tee /etc/modules-load.d/k8s.conf
overlay
br_netfilter
EOF

modprobe overlay
modprobe br_netfilter

# sysctl params required by setup, params persist across reboots
cat <<EOF | 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

# Apply sysctl params without reboot
sysctl --system

# verify
lsmod | grep br_netfilter
lsmod | grep overlay
sysctl net.bridge.bridge-nf-call-iptables net.bridge.bridge-nf-call-ip6tables net.ipv4.ip_forward

enable cri-o
- ```
systemctl enable --now crio
```
enable kubelet
- ```
systemctl enable --now kubelet
```

prepare kubeadm.conf.yaml

---
apiVersion: kubeadm.k8s.io/v1beta3
kind: InitConfiguration
nodeRegistration:
  criSocket: unix:///var/run/crio/crio.sock
  imagePullPolicy: IfNotPresent
  name: k8s-master
  kubeletExtraArgs:
    resolv-conf: /run/systemd/resolve/resolv.conf

---
apiVersion: kubeadm.k8s.io/v1beta3
kind: ClusterConfiguration
clusterName: kubernetes
controllerManager:
  extraArgs:
    node-cidr-mask-size: "16"
imageRepository: registry.k8s.io
kubernetesVersion: 1.28.0
networking:
  dnsDomain: cluster.local
  serviceSubnet: 10.96.0.0/12
  podSubnet: 10.244.0.0/16

---
apiVersion: kubelet.config.k8s.io/v1beta1
kind: KubeletConfiguration
resolvConf: /run/systemd/resolve/resolv.conf

initialize the cluster

with-image-mirror

sed -i 's/imageRepository: .*/imageRepository: m.daocloud.io\/registry.k8s.io/g' kubeadm.conf.yaml
kubeadm init --config kubeadm.conf.yaml

without-image-mirror

kubeadm init --config kubeadm.conf.yaml

copy kubeconfig to local

# can be run by any user with sudo privilege
mkdir -p $HOME/.kube \
    && sudo cp /etc/kubernetes/admin.conf $HOME/.kube/config \
    && sudo chown $UID:$UID $HOME/.kube/config

allow control plane node to run pods

kubectl taint nodes --all node-role.kubernetes.io/control-plane-

install pod network(chose one of the methods below)

flannel by kubectl

# If you use custom podCIDR (not 10.244.0.0/16) you first need to download the above manifest and modify the network to match your one.
kubectl apply -f https://github.com/flannel-io/flannel/releases/latest/download/kube-flannel.yml

flannel by helm chart
calico by helm chart

test with deployment

prepare nginx-deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: docker.io/library/nginx:1.24.0-alpine
        ports:
        - containerPort: 80

apply to cluster
- ```
kubectl apply -f nginx-deployment.yaml
```
check pods
- ```
kubectl get pod
```

troubles

"cni0" already has an IP address different from 10.2.44.1/24
- https://github.com/kubernetes/kubernetes/issues/39557#issuecomment-457839765
- ```
ip link delete cni0
```

uninstallation

uninstall by kubeadm
- ```
kubeadm reset
```