K3s makes use of containerd as the default container platform but I opted to go with docker since I want to become more familiar with it. Note that at this time docker is still considered experimental with k3s as written in the official documentation but I still went on with it anyway. In the following steps I also included how you can execute the kubectl commands without the need of sudo and how they can be executed from a remote machine.

Installation on master node

I have the following setup at the moment where my cluster has a node subnet of 20.0.0.0/24.

Before anything else, modify the hosts on file on each node to reflect the IP and hostnames of the your entire cluster:

127.0.0.1 localhost
20.0.0.10 k8s-master m
20.0.0.11 k8s-worker-1 w1
20.0.0.12 k8s-worker-2 w2

Update and upgrade ubuntu packages:

sudo apt update
sudo apt upgrade
sudo reboot

Install required tools and docker on both master and worker nodes. First add the docker repository.

sudo apt update
sudo apt install apt-transport-https ca-certificates curl software-properties-common -y
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu focal stable"

Install docker:

sudo apt update && sudo apt install -y docker-ce

Run docker and enable persistence in case of server reboot:

sudo systemctl start docker
sudo systemctl enable docker

Check if docker is running:

sudo systemctl status docker

Install k3s on the master node:

curl -sfL https://get.k3s.io | sh -s - --docker

Check status of k3s:

sudo systemctl status k3s

Check if node is running:

sudo kubectl get node -o wide

As an optional step, unblock ports used by kubernetes. By default firewall will be inactive but in case you have enabled it previously, then you need to perform the following:

sudo ufw allow 6443/tcp
sudo ufw allow 443/tcp

You can also check the status of your firewall with:

ufw status

Disable with:

ufw disable

Extract the token to be used for joining worker nodes:

sudo cat /var/lib/rancher/k3s/server/node-token

Installation on worker node

Next is to install k3s on the worker nodes. Here you will need the master node IP address as well as the token from the previous step.

curl -sfL http://get.k3s.io | K3S_URL=https://<master_IP>:6443 K3S_TOKEN=<join_token> sh -s - --docker

Verify all nodes are joined to the cluster

sudo kubectl get nodes -o wide

Now you can try to deploy a test nginx pod

sudo kubectl run --image nginx nginx-test
sudo kubectl get pod nginx-test -o wide

Permit non-root user to execute kubectl commands

Now if you try to execute kubectl commands without sudo, you would probably face the error below.

This is because kubernetes will be installed with root credentials and any other user to execute kubectl will have to be permitted. The easy way is to copy the k3s.yaml file in the /etc/rancher/k3s directory to your user’s kube config file. First create the directory (with your non-root user) if you don’t have it yet. Note of the user and group variables:

mkdir ~/.kube
cp /etc/rancher/k3s/k3s.yaml ~/.kube/config
chown <user>:<group> ~/.kube/config

Then you have to export the kube config every time so to do this automatically upon login modify your .bashrc and add the line:

export KUBECONFIG=~/.kube/config

For you to be able to execute kubectl commands with just typing ‘k’ you can also add the following:

source <(kubectl completion bash)
alias k=kubectl
complete -o default -F __start_kubectl k

Lastly if you want to be able to execute kubectl commands from a remote machine outside your cluster just ensure you have the same kube config file in the previous step and change the server IP from localhost to the actual one.

Ubuntu Server Installation

You can download the Ubuntu iso image from this page. It’s either you download to your local machine or using Unraid with the help of the CLI or some docker app.

While waiting for the download to complete. Go to Settings > VM Manager and set ‘Enable VMs’ to yes. You can also toggle the advanced view to have a more detailed look on the settings. Here you will see the directory of the iso files and the storage so be sure to have your shares properly configured.

Just to give you an idea my iso directory is saved to a cache that doesn’t have redundancy. Image files that are not intended to be used any sooner can either be deleted or transferred to an archive directory on your main array.

It is important to transfer the iso file to the iso share or else you won’t be able to select this later on.

Go to VMs > Add VM > Ubuntu. Select the CPU cores and memory as well as the ISO file.

Assign the disk size.

For network model ensure that br0 is selected. For VM console port Unraid starts with the default port of VNC but just to avoid any conflict later on when you run appliances on GNS3 just choose a different port range from 5900. Uncheck ‘Start VM after creation’. Everything else can be kept in default. Create the VM.

Note network-model should be set to virtio-net to avoid any networking issues with the docker containers.

Go back and edit this VM and toggle from form to XML view on the upper right hand side. To enable nested virtualization insert the following line in the part.

<feature policy='require' name='vmx'/>

Update, start the VM, and open the console. Install the OS how you normally do it.

As for me I always choose Ubuntu Server (not minimized) everytime to avoid any package dependencies later on.

Be sure the VM is assigned a DHCP IP when you get to the network settings or assign a static one if you wish. I always prefer the latter.

Modify disk to utilize all. There really is no use case to use LVM if you are just running GNS3 server.

Also ensure OpenSSH to be installed!

Reboot the server after installation and check your IP within the VNC console. Try to login via ssh.

Perform basic checks especially the disk space! The root directory should be assigned the biggest chunk of the disk size.

Install GNS3 Server

I am sharing the link to the official documentation here for reference. It says to execute the following commands as root:

sudo -i
cd /tmp
curl https://raw.githubusercontent.com/GNS3/gns3-server/master/scripts/remote-install.sh > gns3-remote-install.sh
bash gns3-remote-install.sh --with-openvpn --with-iou --with-i386-repository

Now if we check the status of the gns3 services. It would always show it’s activating

If you check the log file mentioned there you would see the following

CRITICAL web_server.py:88 Could not start the server: [Errno 99] error while attempting to bind on address (‘172.16.253.1’, 3080): cannot assign requested address

Let’s check the configuration file getting loaded and see if we can see anything there.

The controller config file can be found in the highlighted path shown above. At the same time we can see GNS3 is trying to listen on 172.16.253.1.

This seems to be the default IP configured in the installation. Change this to the local IP of your VM.

Restart GNS3 and check the status again. It should be running now.

At this point you should be able to connect from a remote GNS3 GUI to this server.

Lastly to start GNS3 server automatically every reboot, just enable the service:

systemctl enable gns3