In this Kubeadm tutorial, we'll explore everything you need to know about Kubeadm commands and how to use them to create clusters & manage cluster components in (K8s). Kubernetes You'll not only learn how to create your own Kubernetes cluster using Kubeadm, but you’ll also master the art of managing cluster components, and discover Kubeadm's best practices. Join us on this exciting journey into the world of Kubeadm, where you'll unlock the power to with ease. orchestrate containers Let's dive in and become Kubeadm experts together! Before we dive deep into , what exactly is self-hosted Kubernetes (K8s)? kubeadm Content Overview What is Self-hosted Kubernetes? - Pros and Cons What is Kubeadm? Kubeadm Examples Top 20 Most Common Kubeadm Commands How to Create Kubernetes Cluster Using Kubeadm How to Manage Cluster Components with Kubeadm Kubeadm Best Practices What is Self-hosted Kubernetes? - Pros and Cons Self-hosted Kubernetes, also known as a "bare metal" or "on-premises" Kubernetes deployment, refers to running Kubernetes directly on physical or virtual machines without relying on a managed Kubernetes service provided by a cloud provider (such as EKS by AWS). Here are some pros and cons of self-hosted Kubernetes: Pros of Self-hosted Kubernetes 1. Full Control and Customization With self-hosted Kubernetes, you have complete control over the cluster configuration, networking, and infrastructure. This allows you to customize and optimize the cluster according to your specific requirements and infrastructure capabilities. 2. Cost Efficiency Self-hosting Kubernetes can be more cost-effective, especially for long-term deployments, compared to using managed Kubernetes services that often incur additional fees. Self-hosting allows you to leverage existing hardware resources and avoid the overhead costs of managed services. (and save a ton of money) 3. Security and Compliance Self-hosting Kubernetes gives you direct control over security measures, such as network policies, encryption, access controls, and compliance requirements. This allows you to implement the specific to your organization's needs and regulatory standards. (log4j, ring any bells?) best Kubernetes security practices 4. Resource Allocation Self-hosted Kubernetes allows you to allocate resources exclusively to your cluster without sharing them with other tenants. This enables better resource utilization and avoids potential performance issues that may arise from resource contention in a shared environment. Cons of Self-hosted Kubernetes 1. Infrastructure Management Self-hosting Kubernetes requires expertise in managing and maintaining the underlying infrastructure. You are responsible for provisioning, configuring, and monitoring the servers, networking, storage, and other components of the cluster. This can be time-consuming and require dedicated resources and additional hiring. 2. Scalability and Elasticity Scaling self-hosted Kubernetes clusters can be more complex compared to managed services that offer automated scaling capabilities. You need to plan and provision resources in advance to handle peak loads, and adding or removing nodes may require manual intervention. 3. Operational Complexity Self-hosted Kubernetes introduces additional operational complexities, such as managing upgrades, patches, backups, and high availability. These tasks require careful planning, testing, and coordination to ensure minimal disruption to the cluster and applications or else an increase in production downtime. What is Kubeadm? Kubeadm is a command-line tool that simplifies the process of setting up and managing a Kubernetes cluster, making it easier for technical community members to dive into the world of container orchestration. Think of as your trusty assistant who takes care of the nitty-gritty details of , allowing you to focus on the bigger picture. kubeadm cluster setup It automates complex tasks like configuring essential components, generating certificates, and ensuring your cluster follows best practices. Kubeadm Examples Let's take a look at some examples and commands to better understand how works. kubeadm 1. Initializing the Control Plane Example Command #1: ` ` kubeadm init Here's how to use the above command. kubeadm init --pod-network-cidr=192.168.0.0/16 This command initializes the control plane on the master node. It generates necessary certificates, sets up the API server, etcd, and other vital components. The ` ` flag specifies the IP address range for the pod network in the cluster. --pod-network-cidr 2. Joining Worker Nodes Example Command #2: ` ` kubeadm join kubeadm join <master-node-ip>:<master-node-port> --token <token> --discovery-token-ca-cert-hash <hash> This command joins a worker node to the cluster. You need to provide the IP and port of the master node, along with a token and discovery token CA certificate hash, which can be obtained during the control plane initialization. 3. Resetting a Cluster Command: ` ` kubeadm reset kubeadm reset --force This command resets a cluster, removing all the installed components and returning the node to its pre-Kubernetes state. The ` ` flag ensures a thorough reset. --force 4. Upgrading Kubernetes Version Command: ` ` kubeadm upgrade Here's how to use the above command. kubeadm kubeadm upgrade plan This command helps you upgrade your Kubernetes version. It checks for available upgrades and provides a plan for upgrading the control plane components. Top 20 Most Common Kubeadm Commands Here is a list of commonly used kubeadm commands, followed by a relevant example. 1. kubeadm init kubeadm init --pod-network-cidr=192.168.0.0/16 In the above example, the command initializes the control plane on the master node, generating certificates and setting up essential components. The ` ` flag specifies the pod network IP address range. --pod-network-cidr 2. kubeadm join kubeadm join <master-node-ip>:<master-node-port> --token <token> --discovery-token-ca-cert-hash <hash> The above command joins a worker node to the cluster by connecting to the specified master node using a token and discovery token CA certificate hash. 3. kubeadm reset kubeadm reset --force The above command resets a node, removing all installed Kubernetes components and returning it to its pre-Kubernetes state. The ` ` flag ensures a thorough reset. --force 4. kubeadm upgrade kubeadm upgrade plan The above command provides an upgrade plan, checking for available upgrades for the control plane components. 5. kubeadm token kubeadm token create This kubeadm command manages authentication tokens used for joining nodes to the cluster. This example generates a new token. 6. kubeadm config kubeadm config print init-defaults The above command manages kubeadm configuration files. This example prints the default configuration for cluster initialization. 7. kubeadm version kubeadm version The above command prints the version of kubeadm. 8. kubeadm config images kubeadm config images list Use the above command to print a list of images required for the current Kubernetes version. This command helps you determine the required for manual container image management. Replace ` ` with ` ` to pull config images. container images list pull 9. kubeadm token create kubeadm token create --print-join-command The above command generates a new token that can be used to join nodes to the cluster. The ` ` flag displays the join command to be executed on worker nodes. --print-join-command 10. kubeadm token list kubeadm token list The above command lists the active tokens along with their associated creation time and expiration. 11. kubeadm token delete kubeadm token delete <token_value> Use the above command to delete a specific token, rendering it unusable for node joins. 12. kubeadm config migrate kubeadm config migrate --old-config kubeadm.conf --new-config kubeadm.yaml The above command migrates a configuration file from an old version to a new version, enabling smooth upgrades of the configuration. 13. kubeadm certs kubeadm certs check-expirationkubeadm certs certificate-key The above commands check the expiration status of certificates used by the control plane components and provide warnings for certificates nearing expiration. The second command generates the key. 14. kubeadm init phase kubeadm init phase kubelet-start --config config.yaml From an InitConfiguration file, the above command creates a dynamic environment file with kubelet flags. 15. kubeadm join phase kubeadm join phase control-plane-prepare The above command executes a specific phase during the joining of a worker node to the control plane. This example runs the ` ` phase, which prepares the worker node to become a control plane node. control-plane-prepare 16. kubeadm kubeconfig kubeadm kubeconfig user --client-name=foo --config=bar Use the above command to output a file for an additional user named using a kubeadm config file bar. kubeconfig foo 17. kubeadm reset phase kubeadm reset phase preflight The above command executes a specific phase during the reset process of a node. This example runs the ` ` phase, which performs pre-reset checks before removing the Kubernetes components. preflight 18. kubeadm upgrade plan kubeadm upgrade plan The above command displays an upgrade plan for the control plane components, showing available versions and any required actions for the upgrade. 19. kubeadm upgrade apply kubeadm upgrade apply v1.22.2 Use the above command to apply a specific Kubernetes version to the control plane, upgrading its components to the specified version. 20. kubeadm upgrade node kubeadm upgrade node This command upgrades the and on a worker node to match the control plane's version. kubelet kube-proxy How to Create Kubernetes Cluster Using Kubeadm To create a Kubernetes cluster using , you need to ensure that your environment meets the necessary prerequisites. kubeadm Here's a step-by-step guide on how to create a Kubernetes cluster using , including the prerequisites, detailed instructions, examples, and commands. kubeadm Prerequisites Two or more machines running a supported Linux distribution (e.g., Ubuntu, CentOS, or Red Hat Enterprise Linux) with Docker installed. 2 GiB or more of RAM per machine is recommended; anything less leaves limited room for your software. Disable swap space on all machines. Set up a unique hostname, MAC address, and product_uuid for each machine. All machines in the cluster have complete network connectivity. You can connect to a public or private network. Open necessary ports (e.g., 6443, 2379-2380, 10250, 10251, 10252) in your firewall. Step 1: Install Docker and Kubernetes Tools On all machines, install using the for your Linux distribution. Docker Docker guide Install ` `, ` `, and ` ` using the following commands on all machines: kubeadm kubelet kubectl sudo apt-get update && sudo apt-get install -y apt-transport-https curlcurl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -echo "deb https://apt.kubernetes.io/ kubernetes-xenial main" | sudo tee /etc/apt/sources.list.d/kubernetes.listsudo apt-get updatesudo apt-get install -y kubelet kubeadm kubectlsudo apt-mark hold kubelet kubeadm kubectl Step 2: Initialize the Kubernetes Control Plane On the desired control plane node, initialize the cluster using the` ` command: kubeadm init sudo kubeadm init --pod-network-cidr=192.168.0.0/16 Note: Adjust the ` ` flag if you plan to use a different pod network. --pod-network-cidr After the initialization is complete, the command will output a ` ` command with a token and hash. Make sure to copy this command as it will be used to join worker nodes to the cluster later. kubeadm join Step 3: Set Up Cluster Configuration for kubectl On the control plane node, create the necessary directory and copy the file: kubeconfig mkdir -p $HOME/.kubesudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/configsudo chown $(id -u):$(id -g) $HOME/.kube/config Step 4: Deploy a Pod Network Addon On the control plane node, deploy a pod network add-on. For example, you can use Calico: kubectl apply -f https://docs.projectcalico.org/v3.21/manifests/calico.yaml Step 5: Join Worker Nodes in the Cluster On each worker node, run the ` ` command that was generated during the control plane initialization (from Step 2). This command typically looks like this: kubeadm join sudo kubeadm join <control_plane_IP>:6443 --token <token> --discovery-token-ca-cert-hash <hash> Step 6: Verify the Cluster On the control plane node, check the status of the cluster using ` `: kubectl kubectl get nodes Congratulations! You have successfully created a Kubernetes cluster using ` `. You can now deploy and manage your applications on the cluster. kubeadm How to Manage Cluster Components with kubeadm To manage cluster components with , you can use various commands to perform tasks such as upgrading the cluster, adding or removing nodes, and managing the control plane. kubeadm Here's a step-by-step guide on how to manage cluster components with , including detailed commands with code comments. kubeadm Step 1: Upgrading the Cluster Check the current version of Kubernetes on the control plane node: kubectl version --short Upgrade ` `, ` `, and ` ` on all nodes to match the desired Kubernetes version: kubeadm kubelet kubectl # Upgrade kubeadmsudo apt-get updatesudo apt-get install -y kubeadm=<desired_version># Upgrade kubelet and kubectlsudo apt-get updatesudo apt-get install -y kubelet=<desired_version> kubectl=<desired_version># Hold the packages to prevent automatic upgradessudo apt-mark hold kubeadm kubelet kubectl On the control plane node, initiate the upgrade process: sudo kubeadm upgrade plansudo kubeadm upgrade apply <desired_version> Upgrade the kubelet configuration on all nodes: sudo kubeadm upgrade node Verify the upgrade status: kubectl get nodeskubectl version --short Step 2: Adding Worker Nodes On the control plane node, generate a new command: kubeadm join sudo kubeadm token create --print-join-command On the worker node(s), run the command to join them to the cluster: kubeadm join sudo kubeadm join <control_plane_IP>:6443 --token <token> --discovery-token-ca-cert-hash <hash> Verify the status of the new worker nodes: kubectl get nodes Step 3: Removing Nodes Drain the node you want to remove: kubectl drain <node_name> --ignore-daemonsets On the control plane node, remove the node: sudo kubeadm reset On the control plane node, delete the node from the cluster: kubectl delete node <node_name> Step 4: Managing Control Plane Components Upgrade the control plane components on the control plane node: sudo apt-get update  sudo apt-get install -y kubeadm=<desired_version> kubelet=<desired_version> kubectl=<desired_version>  sudo kubeadm upgrade plan  sudo kubeadm upgrade apply <desired_version>  sudo systemctl restart kubelet Verify the upgrade status: kubectl get nodes  kubectl version --short Drain the control plane node you want to remove: kubectl drain <control_plane_node> --ignore-daemonsets On the control plane node, remove the control plane components using the following command. kubeadm sudo kubeadm reset On the control plane node, delete the control plane node from the cluster: kubectl delete node <control_plane_node> Note: Managing cluster components with requires caution, as it can impact the stability and availability of the cluster. Ensure you have a backup plan and follow the official Kubernetes documentation for detailed instructions specific to your setup and requirements. kubeadm Kubeadm Best Practices When used for its intended purposes, Kubeadm is an excellent tool. Here are three best practices to remember in order to use the proper tool for the job and get the most out of kubeadm. Use kubeadm only for production clusters that need autoscaling In general, kubeadm should not be utilized for production clusters because it lacks node and cluster autoscaling capability. This is due to the fact that node autoscaling necessitates controlling underlying infrastructure and hardware, which kubeadm delegated to other tools. Backup etcd on a regular basis Kubeadm does not have a multi-etcd cluster by default for storing cluster state. Make regular backups of etcd in case something goes wrong. Keep track of machines/nodes Kubeadm cannot power off machines that are not in use. So, in order to cluster using , you'll need to use an external solution to track worker nodes and their resource utilization. optimize cost in Kubernetes kubeadm Also published here. The lead image for this article was generated by via the prompt "containers" HackerNoon's AI Image Generator

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