This small setup can be used to provision Flatcar nodes on your Linux laptop with the libvirt provider.
A new disk volume pool will be created in /var/tmp as precaution to not modify the base image by accident. In contrast to the other libvirt setup, the instance user data will be updated by replacing the file contents and forcing QEMU to exit and start again.
It is an experiment to show how to circumvent instance replacement when updating the node user data by replacing just the user-data contents and telling Ignition to rerun on the node. This only works when the Ignition config contains a directive to reformat the root filesystem, so that no old state is kept. The advantage is to be able to keep persistent data on another partition, keep the same IP address, and to reduce the time of re-applying a configuration change. Drawbacks are changing SSH host keys and due to a current limitation an additional reboot when provisioning the first time.
First, prepare the base image and make sure you don't boot it via the flatcar_production_qemu.sh script or similar:
cd ~/Downloads
wget https://stable.release.flatcar-linux.net/amd64-usr/current/flatcar_production_qemu_image.img.bz2
bunzip2 flatcar_production_qemu_image.img.bz2
mv flatcar_production_qemu_image-libvirt-import.img
# optional, increase the image by 5 GB:
qemu-img resize flatcar_production_qemu_image-libvirt-import.img +5G
It will only be used once for the import and can be deleted afterwards even when new VMs are added.
Edit the Container Linux Config cl/machine-mynode.yaml.tmpl file if you like, then create the following terraform.tfvars with a machine mynode, corresponding to the Container Linux Config file name. If you add more machines, create new files for them under cl/.
base_image = "file:///home/myself/Downloads/flatcar_production_qemu_image-libvirt-import.img"
cluster_name = "mycluster"
machines = ["mynode"]
virtual_memory = 768
ssh_keys = ["ssh-rsa AA... [email protected]"]
Now run Terraform (version 13) as follows:
terraform init
terraform apply
View the VMs in virt-manager where you can see the VGA console.
Log in via ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null core@IPADDRESS.
Make a change to cl/machine-mynode.yaml.tmpl and run terraform apply again, seeing how the node is just rebooted and the new config applied.