How to Install K3s as a local development Kubernetes cluster

Install a local Kubernetes cluster using K3s a Lightweight Kubernetes

K3s.io is a Lightweight Kubernetes cluster perfect for development or edge deployments. K3s is a CNCF Sandbox Project Originally developed by Rancher.

Install K3s

To install follow the official installation instructions or run the quick-start script.

Check the script content for security before running it!

Kubeconfig security

Allow no root users to access the Kubernetes file.

The INSTALL_K3S_EXEC environment variable is included with the parameter --write-kubeconfig-mode=644 to set the kubeconfig file /etc/rancher/k3s/k3s.yaml group and world-readable.

Advanced configuration

See K3s Configuration Options for advanced command line installation options.

Command line installation of K3s

$ sudo curl -sfL https://get.k3s.io | INSTALL_K3S_EXEC="server --write-kubeconfig-mode=644" sh -
[sudo] password for user: 
[INFO]  Finding release for channel stable
[INFO]  Using v1.27.7+k3s2 as release
[INFO]  Downloading hash https://github.com/k3s-io/k3s/releases/download/v1.27.7+k3s2/sha256sum-amd64.txt
[INFO]  Downloading binary https://github.com/k3s-io/k3s/releases/download/v1.27.7+k3s2/k3s
[INFO]  Verifying binary download
[INFO]  Installing k3s to /usr/local/bin/k3s
[INFO]  Skipping installation of SELinux RPM
[INFO]  Skipping /usr/local/bin/kubectl symlink to k3s, already exists
[INFO]  Skipping /usr/local/bin/crictl symlink to k3s, already exists
[INFO]  Skipping /usr/local/bin/ctr symlink to k3s, command exists in PATH at /usr/bin/ctr
[INFO]  Creating killall script /usr/local/bin/k3s-killall.sh
[INFO]  Creating uninstall script /usr/local/bin/k3s-uninstall.sh
[INFO]  env: Creating environment file /etc/systemd/system/k3s.service.env
[INFO]  systemd: Creating service file /etc/systemd/system/k3s.service
[INFO]  systemd: Enabling k3s unit
Created symlink /etc/systemd/system/multi-user.target.wants/k3s.service → /etc/systemd/system/k3s.service.
[INFO]  systemd: Starting k3s

Check the Kubernetes Context

Check that the Kubernetes cluster is running by requesting information about the nodes:

$ kubectl get nodes
NAME    STATUS   ROLES                  AGE   VERSION
xps13   Ready    control-plane,master   15d   v1.27.7+k3s2

A kubeconfig is a configuration file used by kubectl, the command-line tool for interacting with Kubernetes clusters. This file stores information about clusters, authentication details, context, and other settings needed to communicate with a Kubernetes cluster. It specifies the cluster's API server, authentication methods (such as certificates or tokens), and the default namespace for operations. The kubeconfig file allows users to manage multiple clusters and switch between them easily using kubectl.

Check the name of the Kubernetes context by requesting information about the kubeconfig file:

$ kubectl config view
apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: DATA+OMITTED
    server: https://127.0.0.1:6443
  name: default
contexts:
- context:
    cluster: default
    user: default
  name: default
current-context: default
kind: Config
preferences: {}
users:
- name: default
  user:
    client-certificate-data: DATA+OMITTED
    client-key-data: DATA+OMITTED

In this example the Kubernetes cluster name is default.

Troubleshooting

Access to the Kubeconfig

Different applications like OpenTofu, Terraform, or the VS Code Kubernetes extension that run without sudo need access to the kubeconfig file.

WARN[0000] Unable to read /etc/rancher/k3s/k3s.yaml, please start server with --write-kubeconfig-mode to modify kube config permissions.

Options:

• Reinstall K3s adding --write-kubeconfig-mode 644 during installation (See INSTALL_K3S_EXEC above)
• Manually give read permissions to everybody (repeat every time k3s is restarted):
  
  $ sudo chmod 644 /etc/rancher/k3s/k3s.yaml

For adding or modifying clusters in the Kubeconfig, use a root user or prefix the kubectl config command with sudo, example:

$ sudo kubectl config set-cluster ditwl-eks-01 --server=https://EA21C5BB81C481ED63221F7D963D.gr7.us-east-1.eks.am
azonaws.com 
Cluster "ditwl-eks-01" set.

Wrong Kubeconfig

OpenTofu and Terraform, or the VS Code Kubernetes extension expect Kubeconfig file to be at the default location $HOME/. kube/config but K3s uses a different location.

For OpenTofu and Terraform set the path in the Provider:

provider "kubernetes" {

  #kubeconfig file, if using K3S set the path
  config_path = "/etc/rancher/k3s/k3s.yaml"
}

For VS Code Kubernetes extension, manually select the location of Kubeconfig using the extension menu (click on ...)

Next Steps

• Deploy a Kubernetes Container with Terraform