Kubeadm is a tool provided by Kubernetes for bootstrapping a cluster. It provides a step-by-step process for initializing a master node, joining worker nodes to the cluster, and deploying the control plane components. Bootstrapping a cluster with kubeadm involves installing the necessary components, initializing the master node, joining worker nodes to the cluster, configuring networking, deploying addons, and verifying the cluster. Kubeadm provides a simple and flexible process for bootstrapping a cluster, and is a good choice for organizations that need to deploy a small- to medium-sized cluster quickly and easily.
Basic steps for bootstrapping a cluster with kubeadm:
- Install the necessary components: You need to install Docker, kubectl, and kubeadm on all nodes in the cluster.
- Initialize the master node: Use the kubeadm init command to initialize the master node. This will create the necessary configuration files and start the control plane components.
- Join worker nodes to the cluster: Once the master node is initialized, you can join worker nodes to the cluster by running the kubeadm join command on each worker node.
- Configure networking: You need to configure the networking for the cluster to ensure that the nodes can communicate with each other. This includes setting up a virtual IP address for the master node and configuring the firewall rules to allow traffic to flow between the nodes.
- Deploy addons: You can use kubeadm to deploy addons, such as the Kubernetes dashboard and network plugins, to the cluster.
- Verify the cluster: Use the kubectl command to verify that the nodes and components are healthy and running correctly.
To install kubeadm, kubelet, and kubectl on a Linux machine, you need to perform the following steps:
- Update the package index: Run the command
sudo apt-get updateon Ubuntu-based systems orsudo yum updateon CentOS-based systems to update the package index. - Install Docker: You need to have Docker installed on your machine in order to use kubeadm. You can follow the instructions for installing Docker for your Linux distribution.
- Add the Kubernetes repository: You need to add the Kubernetes repository to your package manager in order to install kubeadm, kubelet, and kubectl. On Ubuntu-based systems, you can add the repository by running the command
sudo apt-get install -y apt-transport-https curl. On CentOS-based systems, you can add the repository by running the commandsudo tee /etc/yum.repos.d/kubernetes.repo <<EOF. - Install kubeadm, kubelet, and kubectl: You can install kubeadm, kubelet, and kubectl by running the command
sudo apt-get install -y kubeadm kubelet kubectlon Ubuntu-based systems orsudo yum install -y kubeadm kubelet kubectlon CentOS-based systems. - Initialize the cluster: Once kubeadm is installed, you can initialize the cluster by running the command
sudo kubeadm init.
Join worker nodes to the cluster: Once the master node is initialized, you can join worker nodes to the cluster by running the kubeadm join command on each worker node.
Note: To install kubeadm, kubelet, and kubectl on a Linux machine, you need to update the package index, install Docker, add the Kubernetes repository, install kubeadm, kubelet, and kubectl, and initialize the cluster. By following these steps, you can install the necessary components and set up a basic cluster quickly and easily.
kubeadm will not install or manage kubelet or kubectl for you, so you will need to ensure they match the version of the Kubernetes control plane you want kubeadm to install for you. If you do not, there is a risk of a version skew occurring that can lead to unexpected, buggy behaviour. However, one minor version skew between the kubelet and the control plane is supported, but the kubelet version may never exceed the API server version.