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Install using k0sctl

k0sctl is a command-line tool for bootstrapping and managing k0s clusters. k0sctl connects to the provided hosts using SSH and gathers information on the hosts, with which it forms a cluster by configuring the hosts, deploying k0s, and then connecting the k0s nodes together.

k0sctl deployment

With k0sctl, you can create multi-node clusters in a manner that is automatic and easily repeatable. This method is recommended for production cluster installation.

Note: The k0sctl install method is necessary for automatic upgrade.

Prerequisites

You can execute k0sctl on any system that supports the Go language. Pre-compiled k0sctl binaries are available on the k0sctl releases page).

Note: For target host prerequisites information, refer to the k0s System Requirements.

Install k0s

1. Install k0sctl tool

k0sctl is a single binary, the instructions for downloading and installing of which are available in the k0sctl github repository.

2. Configure the cluster

  1. Run the following command to create a k0sctl configuration file:

    k0sctl init > k0sctl.yaml

    This action creates a k0sctl.yaml file in the current directory:

    apiVersion: k0sctl.k0sproject.io/v1beta1
kind: Cluster
metadata:
  name: k0s-cluster
spec:
  hosts:
  - role: controller
    ssh:
      address: 10.0.0.1 # replace with the controller's IP address
      user: root
      keyPath: ~/.ssh/id_rsa
  - role: worker
    ssh:
      address: 10.0.0.2 # replace with the worker's IP address
      user: root
      keyPath: ~/.ssh/id_rsa

  2. Provide each host with a valid IP address that is reachable by k0ctl, and the connection details for an SSH connection.

Note: Refer to the k0sctl documentation for k0sctl configuration specifications.

3. Deploy the cluster

Run k0sctl apply to perform the cluster deployment:

k0sctl apply --config k0sctl.yaml
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INFO k0sctl 0.0.0 Copyright 2021, Mirantis Inc.
INFO Anonymized telemetry will be sent to Mirantis.
INFO By continuing to use k0sctl you agree to these terms:
INFO https://k0sproject.io/licenses/eula
INFO ==> Running phase: Connect to hosts
INFO [ssh] 10.0.0.1:22: connected
INFO [ssh] 10.0.0.2:22: connected
INFO ==> Running phase: Detect host operating systems
INFO [ssh] 10.0.0.1:22: is running Ubuntu 20.10
INFO [ssh] 10.0.0.2:22: is running Ubuntu 20.10
INFO ==> Running phase: Prepare hosts
INFO [ssh] 10.0.0.1:22: installing kubectl
INFO ==> Running phase: Gather host facts
INFO [ssh] 10.0.0.1:22: discovered 10.12.18.133 as private address
INFO ==> Running phase: Validate hosts
INFO ==> Running phase: Gather k0s facts
INFO ==> Running phase: Download K0s on the hosts
INFO [ssh] 10.0.0.2:22: downloading k0s 0.11.0
INFO [ssh] 10.0.0.1:22: downloading k0s 0.11.0
INFO ==> Running phase: Configure K0s
WARN [ssh] 10.0.0.1:22: generating default configuration
INFO [ssh] 10.0.0.1:22: validating configuration
INFO [ssh] 10.0.0.1:22: configuration was changed
INFO ==> Running phase: Initialize K0s Cluster
INFO [ssh] 10.0.0.1:22: installing k0s controller
INFO [ssh] 10.0.0.1:22: waiting for the k0s service to start
INFO [ssh] 10.0.0.1:22: waiting for kubernetes api to respond
INFO ==> Running phase: Install workers
INFO [ssh] 10.0.0.1:22: generating token
INFO [ssh] 10.0.0.2:22: writing join token
INFO [ssh] 10.0.0.2:22: installing k0s worker
INFO [ssh] 10.0.0.2:22: starting service
INFO [ssh] 10.0.0.2:22: waiting for node to become ready
INFO ==> Running phase: Disconnect from hosts
INFO ==> Finished in 2m2s
INFO k0s cluster version 0.11.0 is now installed
INFO Tip: To access the cluster you can now fetch the admin kubeconfig using:
INFO      k0sctl kubeconfig

4. Access the cluster

To access your k0s cluster, use k0sctl to generate a kubeconfig for the purpose.

k0sctl kubeconfig > kubeconfig

With the kubeconfig, you can access your cluster using either kubectl or Lens.

kubectl get pods --kubeconfig kubeconfig -A
NAMESPACE     NAME                                       READY   STATUS    RESTARTS   AGE
kube-system   calico-kube-controllers-5f6546844f-w8x27   1/1     Running   0          3m50s
kube-system   calico-node-vd7lx                          1/1     Running   0          3m44s
kube-system   coredns-5c98d7d4d8-tmrwv                   1/1     Running   0          4m10s
kube-system   konnectivity-agent-d9xv2                   1/1     Running   0          3m31s
kube-system   kube-proxy-xp9r9                           1/1     Running   0          4m4s
kube-system   metrics-server-6fbcd86f7b-5frtn            1/1     Running   0          3m51s

Known limitations

  • k0sctl does not perform any discovery of hosts, and thus it only operates on the hosts listed in the provided configuration.
  • k0sctl can only add more nodes to the cluster. It cannot remove existing nodes.

Next Steps