I decided to reinstall a Kubernetes cluster at my homelab, and in this article, I am documenting the preparation steps I took.

Node setup

The cluster consists of six nodes: three master nodes and three worker nodes. The operating system is AlmaLinux 9, with each node having a 4-core CPU and 8 GB of RAM.

Preparation Steps

SELinux configuration

Set SELinux to permissive mode and update the configuration to make it persistent:

setenforce 0
sed -i 's/^SELINUX=enforcing/SELINUX=permissive/' /etc/selinux/config

The first command changes SELinux to permissive mode until the next reboot. To make this change permanent, update the /etc/selinux/config file.

Stop/Disable firewall

Stop and disable the firewall to prevent it from starting at boot:

systemctl stop firewalld
systemctl disable firewalld

Note: Disabling the firewall is not recommended for a production environment, as it leaves your system vulnerable to external threats. Instead, configure firewall rules to allow necessary traffic.

Disable Swap

Kubernetes requires swap to be disabled. Use the following commands to stop the swap partition and remove it from the /etc/fstab file:

swapoff -a
sed -i '//dev/mapper/almalinux_alma9--template-swap.*swap/d' /etc/fstab

Configure proxy settings

Since all my servers are behind a proxy and do not have direct Internet access, I configured proxy settings. I added the settings to both the bashrc file and the yum (dnf) configuration file:

echo "proxy=http://192.168.11.51:3128" >> /etc/dnf/dnf.conf
echo "proxy=https://192.168.11.51:3128" >> /etc/dnf/dnf.conf

echo 'export NO_PROXY="127.0.0.1,localhost,192.168.11.0/8"' >> /etc/bashrc
echo 'export http_proxy="http://192.168.11.51:3128"' >> /etc/bashrc
echo 'export https_proxy="http://192.168.11.51:3128"' >> /etc/bashrc

Activating Packet Forwarding

The net.ipv4.ip_forward setting controls whether the Linux kernel forwards IPv4 packets between network interfaces. By default, this value is set to 0, which disables packet forwarding. Setting this value to 1 enables packet forwarding, which is essential for Kubernetes networking.

if ! grep -q '^net.ipv4.ip_forward' /etc/sysctl.conf; then
  echo 'net.ipv4.ip_forward = 1' >> /etc/sysctl.conf
else
  sed -i 's/^net.ipv4.ip_forward.*/net.ipv4.ip_forward = 1/' /etc/sysctl.conf
fi

# Apply the changes
sysctl -p

Update the host and restart

Install additional packages and update the host:

dnf install -y yum-utils device-mapper-persistent-data lvm2 wget
dnf update -y

Restart the host to apply all changes and ensure the new settings take effect:

shutdown -r now

Final thoughts

With these preparation steps complete, the first Kubernetes master node is ready for deployment. Properly configuring SELinux, disabling swap, and setting up proxy settings ensure that the environment is optimized for Kubernetes. The next steps will involve installing the container runtime, Kubernetes components, and setting up the first master node. 

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