Managing Kubernetes Clusters with Rancher and Docker

While initializing Kubernetes clusters via kubeadm provides an excellent starting foundation, managing multiple clusters, RBAC permissions, and multi-tenant workloads purely through kubectl can become incredibly complex.

Rancher is an industry-leading open-source Kubernetes management platform that provides an elegant web-based user interface, centralized IAM integrations, and automated cluster provisioning across multiple cloud providers and bare-metal servers.

In this guide, I will walk you through preparing a CentOS 7 management node, installing Docker CE, deploying Rancher inside a privileged Docker container, and binding persistent storage volumes.

Prerequisites

You will need a dedicated CentOS 7 virtual machine (central-dc1-k8s-rancher.induslevel.com) with root privileges, configured with static IP addressing and a minimum of 4 GB of RAM.

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Step 1: Base System Preparation and Host Resolution

First, update system packages, install necessary utilities, and configure local hostname resolution across your cluster nodes.

# Update system packages
yum update -y

# Install required system utilities
yum install epel-release yum-utils bash-completion net-tools device-mapper-persistent-data lvm2 -y

# Enforce static hostname resolution
cat >> /etc/hosts << "EOF"
10.14.7.51 central-dc1-k8s-master.induslevel.com k8s-master
10.14.7.53 central-dc1-k8s-node01.induslevel.com k8s-node01
10.14.7.54 central-dc1-k8s-node02.induslevel.com k8s-node02
10.14.7.55 central-dc1-k8s-rancher.induslevel.com k8s-rancher
EOF

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Step 2: Disabling Swap and SELinux

Rancher and underlying Kubernetes components require swap memory to be entirely disabled. We also disable SELinux to allow unhindered container network bridging.

# Disable SELinux
sed -i 's/SELINUX=enforcing/SELINUX=disabled/g' /etc/selinux/config

# Turn off active swap and remove fstab mounting
swapoff -a
sed -i.bak -r 's/(.+ swap .+)/#\1/' /etc/fstab

# Verify configuration
free -m
cat /etc/fstab

Reboot the virtual machine to apply the clean kernel baseline:

reboot

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Step 3: Installing Docker CE

Rancher runs as a containerized application. Configure the official Docker CE repository and install the Docker engine.

# Configure Docker CE repository manifest
yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo

# Install Docker engine
yum install -y docker-ce docker-ce-cli containerd.io

# Enable and start Docker daemon
systemctl enable docker
systemctl start docker
systemctl status docker

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Step 4: Deploying Rancher Server Container

With Docker operational, create a persistent host directory to store Rancher configuration data and deploy the Rancher server container in privileged mode.

# Create persistent storage directory
mkdir -p /opt/rancher

# Deploy Rancher server container
docker run -d --restart=unless-stopped -p 80:80 -p 443:443 -v /opt/rancher:/var/lib/rancher --privileged rancher/rancher

Understanding the Deployment Parameters

• --restart=unless-stopped: Ensures Rancher automatically restarts if the Docker daemon or server reboots.
• -p 80:80 -p 443:443: Exposes standard HTTP and HTTPS web management ports.
• -v /opt/rancher:/var/lib/rancher: Binds persistent storage so cluster configurations survive container updates.
• --privileged: Grants Rancher necessary kernel capabilities to manage embedded Kubernetes components.

References

• Rancher Official Documentation