Setting Up Kubernetes v1.28.9 with kubeadm on CentOS 7
Tech
1
This guide walks through deploying a production-ready Kubernetes cluster using kubeadm on CentOS 7, targeting version 1.28.9. The topology consists of one control-plane node and two worker nodes.
Kernel Upgrade for Stability
Older kernel versions may cause unexpected behavior in container runtimes and networking subsystems. Upgrade to the long-term supported (LTS) kernel:
# List current boot entries
awk -F\' '$1=="menuentry " {print i++ " : " $2}' /etc/grub2.cfg
# Import ELRepo GPG key and install repository
rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
yum -y install https://www.elrepo.org/elrepo-release-7.0-4.el7.elrepo.noarch.rpm
# Install LTS kernel
yum --enablerepo="elrepo-kernel" -y install kernel-lt.x86_64
# Set default boot entry to new kernel and regenerate config
grub2-set-default 0
grub2-mkconfig -o /boot/grub2/grub.cfg
# Reboot and verify
reboot
# After reboot:
awk -F\' '$1=="menuentry " {print i++ " : " $2}' /etc/grub2.cfg
Disable Firewall
Ensure consistant network policies by disabling firewalld:
systemctl stop firewalld
systemctl disable firewalld
systemctl status firewalld | grep Active
Disable Swap
Kubernetes requires swap to be disabled:
# Comment out swap lines in fstab and deactivate immediately
sed -i '/swap/d' /etc/fstab
swapoff -a
Disable SELinux
Set SELinux to permissive mode permanently:
sed -i 's/^SELINUX=.*/SELINUX=disabled/' /etc/selinux/config
setenforce 0
Configure Hostname Resolution
Add static host mappings to /etc/hosts. Replace IPs and names as needed:
cat <<EOF >> /etc/hosts
192.168.18.219 master
192.168.18.220 node01
192.168.18.221 node02
EOF
Set Unique Hostnames
Apply appropriate hostnames across nodes:
# On control plane
hostnamectl set-hostname master
# On first worker
hostnamectl set-hostname node01
# On second worker
hostnamectl set-hostname node02
# Confirm and reload network context
hostname
systemctl restart systemd-hostnamed
Synchronize System Time
Use chrony to maintain time consistency across all node:
yum install -y chrony
systemctl enable --now chronyd
chronyc sources -v
# Verify output includes at least one active NTP source
date
