Install K3s node in a Linux Virtual Machine

Update 2023-01-06: –no-deploy traefik has been deprecated, must use –disable traefik

Update 2023-12-07: repository for ingress nginx has changed

Let’s quickly create a K3s environment where you can test and learn to use Kubernetes.

VM Configuration

We’ll be using a Linux virtual machine for this, the tools I will be using are VMware Workstation Player and CentOS 9 Stream on a Windows host. Once you have created your virtual machine, I suggest installing CentOS with the following settings:

• Minimal install
• Manual partitioning:
  • 1GiB, type ext2, mount point /boot
  • 2GiB, type swap
  • the rest of the space, type xfs, mount point /
• Disable root account
• Make your user account administrator

Unless you want to use Server with GUI, I recommend doing a minimal install and use your host computer to connect through SSH, which is bundled with Windows 10 and 11, and any Linux or Mac computer by default. This is to make the Linux VM as small as possible.

Installing K3s

Before installing K3s, I recommend changing your VM hostname, you can do this by running sudo hostnamectl hostname [NAME], being [NAME] whaterever name you want, once you have done this restart the server by running sudo reboot, also remember that you can turn off the server at any time by running sudo poweroff. Once you have logged in with your user again, run sudo su - so we can start installing K3s:

curl -sfL https://get.k3s.io | INSTALL_K3S_EXEC="--disable traefik" sh -s -

This will install K3s without Traefik, in case you want to use ingress-nginx. If you want Traefik anyway, remove the INSTALL_K3S_EXEC="--disable traefik" part and skip the ingress-nginx part below.

Wait around a minute and run kubectl get nodes to check if K3s has installed successfully and is Ready, if it is, you should see something like this:

NAME         STATUS   ROLES                  AGE    VERSION
[VM-HOSTNAME]   Ready    control-plane,master   5m   v1.24.6+k3s1

Then we are going to install helm:

curl -fsSL -o get_helm.sh https://raw.githubusercontent.com/helm/helm/main/scripts/get-helm-3
chmod 700 get_helm.sh
./get_helm.sh

Or you can also install it with just one line:

curl https://raw.githubusercontent.com/helm/helm/main/scripts/get-helm-3 | bash

Then run the following commands to install ingress-nginx:

helm repo add ingress-nginx https://kubernetes.github.io/ingress-nginx

helm repo update

helm install ingress-nginx ingress-nginx/ingress-nginx --namespace ingress-nginx --create-namespace

If you are having problems installing packages with helm because of the following error Error: INSTALLATION FAILED: Kubernetes cluster unreachable: Get "http://localhost:8080/version": dial tcp [::1]:8080: connect: connection refused, then try running the following command (still as sudo su -):

echo "export KUBECONFIG=/etc/rancher/k3s/k3s.yaml" >> ~/.bashrc

Exit your sudo session by running exit, then run sudo su - and try again.

Finally, to avoid problems when trying to access applications, stop and disable firewalld:

systemctl stop firewalld; systemctl disable firewalld

To access applications that you have installed in your K3s instance from your host environment, you have to know your VM IP address and configure in your host operating system the hosts file to associate that IP address with the DNS name that you have configured in your app Ingress. You can check your VM IPv4 address by running the command ip a s | grep 'inet ', the space between inet and the quote is to only show IPv4 addresses, remove it to show IPv6 addresses as well. Then on your host machine hosts file add as many lines for each Ingress you have:

<k3s-vm-ip-addr> myapp01-ingress.name
<k3s-vm-ip-addr> myapp02-ingress.name
<k3s-vm-ip-addr> myapp03-ingress.name

Bonus: install cert-manager

If you want to add cert-manager to your K3s instance, run the following commands:

helm repo add jetstack https://charts.jetstack.io

helm repo update

helm install cert-manager jetstack/cert-manager --namespace cert-manager --create-namespace --version v1.7.1 --set installCRDs=true