Create a Kubernetes Node

This guide walks you through booting a VM from the network and installing Debian 12.x (Bookworm), using a PXE server. Moreover, you will learn how to use a preseed file to automate the installation of Debian 12.x on any VM.

Step 1: Define the Worker VM

In this section, you define a new VM. We will use this as a use case. Then, you can deploy any VM you want to create a Kubernetes cluster (e.g., a control plane, another worker, etc.) using exactly the same process.

What you’ll need

To complete this guide, you will need the following:

A working QEMU/KVM installation.
A configured PXE Server.

Procedure

Follow the steps below to define a new VM:

Create a new QCOW2 virtual disk for the VM:

user:~/virtml$ qemu-img create -f qcow2 /var/lib/libvirt/images/node1.qcow2 96G
Formatting '/var/lib/libvirt/images/node1.qcow2', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=103079215104 lazy_refcounts=off refcount_bits=16

Define a new VM, using the XML file inside the infra directory:
```
user:~/virtml$ virsh define --file infra/node1.xml
Domain 'node1' defined from node1.xml
```
Note

The node1.xml file is a template for the VM. You can modify it to fit your needs. Pay close attention to the sections where you specify the path to the QCOW2 file.

Verify

Verify that the VM has been defined correctly and is in the shut off state:

List the VMs you have defined:

user:~/virtml$ virsh list --all
Id   Name           State
-----------------------------
1    virtml-admin   running
-    node1          shut off

Step 2: Configure the PXE Server

In this section, you configure your PXE Server to repond to request from this specific VM. To achieve this, you use the MAC address of your newly created machine.

What you’ll need

To complete this guide, you will need the following:

A defined worker VM.

Procedure

Decide on login credentials for the root user of new worker VM:
```
user:~/virtml$ export ROOTPW_HASH=$(openssl passwd -6)
```

Export your public SSH key:

user:~/virtml$ export SSH_KEY=$(cat ~/.ssh/id_rsa.pub)

Export the hostname of the node VM:
```
user:~/virtml$ export HOSTNAME=node1
```

Export the domain name of the node VM:

user:~/virtml$ export DOMAIN=example.com

Render the preseed file:

user:~/virtml$ j2 infra/k8s_preseed.cfg.j2 > infra/k8s_preseed.cfg

Copy the preseed file onto the PXE Server:

user:~/virtml$ scp infra/k8s_preseed.cfg root@virtml-admin:/srv/tftp/preseed.cfg

Decide on the IP address and the hostname of the worker VM:

a. Set the VM’s IP address:

user:~/virtml$ export CLIENT_IP=192.168.20.101

b. Set the VM’s MAC address:

user:~/virtml$ export CLIENT_MAC=$(sudo virsh dumpxml node1 | grep "<mac address=" | awk -F"'" '{print $2}')

c. Set the VM’s hostname:

user:~/virtml$ export CLIENT_HOSTNAME=node1

Render the dnsmasq configuration:

user:~/virtml$ j2 infra/dnsmasq.conf.j2 > infra/dnsmasq.conf-01-${CLIENT_MAC//:/-}

Copy the configuration file onto the PXE Server:

user:~/virtml$ scp infra/dnsmasq.conf-01-${CLIENT_MAC//:/-} root@virtml-admin:/etc/dnsmasq.d/dnsmasq.conf-01-${CLIENT_MAC//:/-}

SSH into the PXE server VM:
```
user:~/virtml$ ssh root@virtml-admin
```

Restart the dnsmasq service:

root@virtml-admin:~# systemctl restart dnsmasq

Log out the PXE Server:
```
root@virtml-admin:~# exit
```

Step 3: Start the worker VM

In this final section, you start the worker VM and watch as it boots from the network and installs Debian automatically.

What you’ll need

A defined worker VM.
A configured PXE Server, ready to respond to DHCP discover requests from a spcific MAC address.

Procedure

Start the worker VM:

user:~/virtml$ virsh start node1
Domain 'node1' started

Verify

Connect to the node1 through your terminal and watch as the Debian installer automatically installs the OS, without any human intervention.
```
user:~/virtml$ virsh console node1
```
SSH into the node1 VM:
```
user:~/virtml$ ssh root@node1
```
Note

Replace node1 with the IP address of the VM. Alternatively, you can set the hostname for the VM in your /etc/hosts file.