K0s, pronounced kzeros, is a fully-fledged open-source Kubernetes distribution developed by team Lens – the Kubernetes IDE project. K0s is highly configurable and flexible to cover various Kubernetes uses like local and private data centers, IoT and public cloud clusters, and hybrid deployments. It is a simple, solid and certified Kubernetes distribution that can be deployed on any infrastructure. This means that K0s can run on any private or public cloud environment.
k0s is distributed as a single binary with zero host OS dependencies besides the host OS kernel. It works with any operating system without additional software packages or configuration. Any security vulnerabilities or performance issues can be fixed directly in the k0s distribution.
Features of k0s
K0s is a fully featured Kubernetes deployment and ships with all the features of Kubernetes. Some of these features include:
- Supports latest Kubernetes Versions – later than v1.20.0
- Uses ContainerD runtime as the default but you can configure custom runtime
- Supported Machine Architectures – x86-64, ARM64, ARMv7
- Supported Host OS – Linux (kernel v3.10 or newer), Windows Server 2019 (experimental)
- Control Plane Datastore- In-Cluster Elastic Etcd with TLS (default), In-Cluster SQLite (default for single node), External PostgreSQL, External MySQL
- Supported CNI Providers – Kube-Router (default), Calico, Custom
- Supported Storage & CSI Providers – All Kubernetes storage solutions (with CSI)
- Supported Cloud Providers – All Cloud Providers (via extensions)
- Built-In Security Features – RBAC, Pod Security Policies, Network Policies, Control Plane Isolation, Support for Micro VMs, Support for OpenID Providers
- Built-In Cluster Features- DNS by CoreDNS, Cluster Metrics by Metrics Server, Horizontal Pod Autoscaling (HPA), GPU Support, Zero-Downtime Cluster Upgrade (via k0sctl), Cluster Backup & Restore
Table of Content
- Downloading k0s
- Installing k0s
- Starting k0s service
- Accessing the cluster using kubectl
- Getting cluster conf file
- Testing the cluster by running a simple nginx app
- Uninstalling k0s
Run the k0s download script to download the latest stable version of k0s and make it executable from
curl -sSLf https://get.k0s.sh | sudo sh
You should see output similar to this:
$ curl -sSLf https://get.k0s.sh | sudo sh Downloading k0s from URL: https://github.com/k0sproject/k0s/releases/download/v1.22.2+k0s.1/k0s-v1.22.2+k0s.1-amd64 k0s is now executable in /usr/local/bin
k0s install sub-command installs k0s as a system service on the local host that is running one of the supported init systems: Systemd or OpenRC. You can execute the install for workers, controllers or single node (controller+worker) instances.
Run the following command to install a single node k0s that includes the controller and worker functions with the default configuration:
sudo k0s install controller --single
What this does: includes both controller and worker functions in this vm – acting both as a controller and worker node.
$ sudo k0s install controller --single INFO[2022-01-02 14:09:50] no config file given, using defaults INFO[2022-01-02 14:09:50] creating user: etcd INFO[2022-01-02 14:09:51] creating user: kube-apiserver INFO[2022-01-02 14:09:51] creating user: konnectivity-server INFO[2022-01-02 14:09:51] creating user: kube-scheduler INFO[2022-01-02 14:09:51] Installing k0s service
k8s will store the data in this dir
/var/lib/k0s/, check with
Check the unit service file added with:
$ sudo systemctl list-unit-files | grep k0s k0scontroller.service enabled
k0s install controller sub-command accepts the same flags and parameters as the
Starting k0s service
To start the k0s service, run:
sudo k0s start
You could also do
sudo systemctl start k0scontroller
The k0s service will start automatically after the node restart.
A minute or two typically passes before the node is ready to deploy applications.
To get general information about your k0s instance’s status, run:
sudo k0s status
$ sudo k0s status Version: v1.21.3+k0s.0 Process ID: 51348 Parent Process ID: 1 Role: controller+worker Init System: linux-systemd Service file: /etc/systemd/system/k0scontroller.service
Access your cluster using kubectl
Note: k0s includes the Kubernetes command-line tool
Use kubectl to deploy your application or to check your node status:
sudo k0s kubectl get nodes
$ sudo k0s kubectl get nodes NAME STATUS ROLES AGE VERSION ub-k0s Ready <none> 2m51s v1.21.3+k0ss
You can check cluster-info using this command:
$ sudo k0s kubectl cluster-info Kubernetes control plane is running at https://localhost:6443 CoreDNS is running at https://localhost:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy Metrics-server is running at https://localhost:6443/api/v1/namespaces/kube-system/services/https:metrics-server:/proxy To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.
Getting Cluster conf file
Using the existing admin.conf file
To access the cluster from the host file, you need the
admin.conf file. The file is located in
Use this command to copy to the local file:
scp [email protected]:/var/lib/k0s/pki/admin.conf
For the file to work, you will need to open it with a text editor like
vim and update the server:
clusters: - cluster: server: https://localhost:6443
clusters: - cluster: server: https://192.168.20.7:6443
Then export Config with this command
Test config by checking pods
➜ kubectl get pods -A NAMESPACE NAME READY STATUS RESTARTS AGE kube-system kube-proxy-k7855 1/1 Running 0 21m kube-system kube-router-5x74j 1/1 Running 0 21m kube-system coredns-5ccbdcc4c4-j5kk6 1/1 Running 0 22m kube-system metrics-server-59d8698d9-nbfnt 1/1 Running 0 22m
Check node resource usage using metric server
➜ kubectl top nodes NAME CPU(cores) CPU% MEMORY(bytes) MEMORY% ub-k0s 98m 4% 609Mi 69%
Pods usage using metric server
➜ kubectl top pods -A NAMESPACE NAME CPU(cores) MEMORY(bytes) kube-system coredns-5ccbdcc4c4-j5kk6 3m 12Mi kube-system kube-proxy-k7855 1m 17Mi kube-system kube-router-5x74j 1m 18Mi kube-system metrics-server-59d8698d9-nbfnt 1m 12Mi
Using k0s to generate the cluster config file
Use this command to print out the admin config file
sudo k0s kubeconfig admin sudo k0s kubeconfig admin > admin.conf
Testing the cluster by runing a simple nginx app
Create an nginx deployment
kubectl create deploy nginx --image nginx:latest
kubectl get all
❯ kubectl get all NAME READY STATUS RESTARTS AGE pod/nginx-55649fd747-xnlvv 1/1 Running 0 4m28s NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE service/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 32m service/nginx NodePort 10.106.202.223 <none> 80:30047/TCP 2m27s NAME READY UP-TO-DATE AVAILABLE AGE deployment.apps/nginx 1/1 1 1 4m28s NAME DESIRED CURRENT READY AGE replicaset.apps/nginx-55649fd747 1 1 1 4m28s
Expose as Nodeport
kubectl expose deploy nginx --port 80 --type NodePort
❯ kubectl expose deploy nginx --port 80 --type NodePort service/nginx exposed
Get the service
kubectl get service
➜ kubectl get service NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 30m nginx NodePort 10.106.202.223 <none> 80:30047/TCP 17s
Since the app is mounted to port
30047, pick any node’s IP in the cluster (we only have one node so use its IP) then use it to test using this command.
You should see Nginx welcome page.
Cleaning up nginx app
Delete the service
kubectl delete service
kubectl delete deploy nginx
The removal of k0s is a two-step process.
Stop the service
Use the following command to stop the service
sudo k0s stop
Execute the k0s reset command
The k0s reset command cleans up the installed system service, data directories, containers, mounts and network namespaces.
sudo k0s reset
Reboot the system.
A few small k0s fragments persist even after the reset (for example, iptables). As such, you should initiate a reboot after the running of the k0s reset command.
We managed to set up a k0s cluster in this guide and install some nginx app to test that it is working file.