Cloud-Init

NoCloud datasource docs

Purpose

Overview

Test environment

Step 1: Install QEMU, KVM, and Required Tools

On your Ubuntu Server, you need to install QEMU, KVM, and related tools to manage virtual machines without a graphical interface.

sudo apt update
sudo apt install qemu-kvm libvirt-daemon-system libvirt-clients bridge-utils virtinst virt-manager genisoimage guestfs-tools

Here’s what each component does:

• qemu-kvm: The hypervisor to run virtual machines.
• libvirt-daemon-system: Manages virtual machines using KVM.
• libvirt-clients: Provides command-line tools to manage virtual machines.
• bridge-utils: Allows the VM to access your network.
• virtinst: Command-line utilities for creating virtual machines.
• virt-manager: A GUI for managing virtual machines, though it won’t be needed for now.

Step 2: Enable and Start libvirt

Make sure the libvirtd service is enabled and running:

sudo systemctl enable libvirtd
sudo systemctl start libvirtd

To verify that KVM is installed and running properly:

sudo virsh list --all

This will display an empty list if there are no VMs running, but it confirms the setup is working.

Step 3: Create a Bridge Network for VMs

For the VMs to communicate with the outside network (and for easier SSH access), it’s best to set up a bridged network.

1. Open the network configuration file:

sudo nano /etc/netplan/00-installer-config.yaml

2. Add a bridge interface. Replace eth0 with your network interface:

network:
  version: 2
  renderer: networkd
  ethernets:
    enp0s31f6:      # be sure to specify your actual wan interface
      dhcp4: no     # Disable DHCP on the physical interface
  bridges:
    br0:
      interfaces: [enp0s31f6] # be sure to specify your actual wan interface
      dhcp4: yes    # Enable DHCP on the bridge
      parameters:
        stp: false  # Disable Spanning Tree Protocol for faster convergence
        forward-delay: 0  # Optimize for faster network performance
      optional: true

3. Set proper permissions and apply the changes:

sudo chmod 600 /etc/netplan/00-installer-config.yaml
sudo netplan apply

This sets up a bridge that your VMs can use to access the network.

Step 4: Download an Ubuntu Cloud Image

To test Cloud-init, you can use an Ubuntu Cloud image, which is pre-configured for cloud environments and already optimized for Cloud-init.

1. Download the latest Ubuntu Server Cloud image:

wget https://cloud-images.ubuntu.com/focal/current/focal-server-cloudimg-amd64.img

# in some cases where you want direct access to the console you might want to set a root password
virt-customize -a /var/lib/libvirt/images/focal-server-cloudimg-amd64.img --root-password password:<pass>

2. Move the image to the /var/lib/libvirt/images/ directory for organization:

sudo mv focal-server-cloudimg-amd64.img /var/lib/libvirt/images/

Step 5: Create a Cloud-init ISO

Cloud-init requires an ISO image to pass user-data. We’ll create a user-data and meta-data file and package them into an ISO.

1. Create the user-data file (your Cloud-init config):

nano user-data

Paste your Cloud-init configuration in this file (the one you've prepared earlier).

2. Create the meta-data file (OPTIONAL):

nano meta-data

Add the following contents (you can customize the instance-id and hostname):

instance-id: $(uuidgen)
local-hostname: default-hostname

3. Create an ISO image with user-data and meta-data:

genisoimage -output seed.iso -volid cidata -joliet -rock user-data meta-data

4. Move the iso to the proper location and set permissions

sudo mv /home/sysadmin/seed.iso /var/lib/libvirt/images/
sudo chmod 644 /var/lib/libvirt/images/seed.iso

This will create an ISO file (seed.iso) that Cloud-init can read when the VM is started.

Step 6: Create and Launch the VM

Now that you have both the cloud image and Cloud-init ISO, you can create and launch the VM using virt-install.

sudo virt-install \
  --name ubuntu-cloud-vm \
  --ram 4048 \
  --vcpus 2 \
  --disk path=/var/lib/libvirt/images/focal-server-cloudimg-amd64.img,format=qcow2 \
  --disk path=/var/lib/libvirt/images/seed.iso,device=cdrom \
  --import \
  --os-variant ubuntu24.04 \
  --network bridge=br0 \
  --graphics none \
  --noautoconsole

Here’s a breakdown of what this command does:

• --name: Specifies the VM name.
• --ram: Allocates 2 GB of RAM for the VM.
• --vcpus: Allocates 2 virtual CPUs for the VM.
• --disk: Defines the path to the Ubuntu cloud image and the Cloud-init ISO.
• --import: Skips installation and directly boots the image.
• --os-variant: Specifies the OS variant (use osinfo-query os to see more variants).
• --network: Connects the VM to the bridged network.
• --graphics none: Disables graphical output (we’re running this on a server without a GUI).
• --noautoconsole: Prevents automatic console attachment.

Step 7: Access the VM via SSH

Once the VM is running, find its IP address to access it via SSH:

sudo virsh domifaddr ubuntu-cloud-vm

This should show you the IP address assigned to the VM. You can then SSH into the VM:

ssh sysadmin@<vm-ip-address> -i <path-to-private-key>

Replace <vm-ip-address> with the IP address of the VM and <path-to-private-key> with the path to the private key for the sysadmin user.

Optional: GPU Passthrough for Visual Output

Since you mentioned that you have a GPU, you can enable GPU passthrough for the VM if you want to provide visual output.

1. Enable IOMMU: Add the following line to /etc/default/grub:

GRUB_CMDLINE_LINUX="intel_iommu=on"  # For Intel
# or
GRUB_CMDLINE_LINUX="amd_iommu=on"    # For AMD

Then update Grub:

sudo update-grub

2. Configure GPU Passthrough: You would need to modify the VM XML configuration to pass through the GPU device. You can do this by editing the XML of the VM:

sudo virsh edit ubuntu-cloud-vm

Troubleshooting

1. Run libguestfs-test-tool

First, run the libguestfs-test-tool to diagnose any issues with libguestfs. This tool checks whether your libguestfs environment is set up correctly.

sudo libguestfs-test-tool

This command performs a series of tests. If any errors occur, they should give you insight into what’s wrong with your libguestfs setup.

2. Enable Debugging for virt-customize

You can gather more detailed information by running virt-customize with debugging enabled:

export LIBGUESTFS_DEBUG=1 LIBGUESTFS_TRACE=1
sudo virt-customize -a /var/lib/libvirt/images/focal-server-cloudimg-amd64.img --root-password password:test

This will provide more detailed output and help identify where the issue lies.

3. Check KVM and QEMU Setup

virt-customize relies on KVM/QEMU to create a temporary VM to modify the disk. Ensure that KVM and QEMU are working correctly.

1. Check if KVM is enabled:

egrep -c '(vmx|svm)' /proc/cpuinfo

You should see a non-zero result (indicating KVM support). If it’s zero, you need to enable virtualization in your BIOS.

2. Ensure that the kvm modules are loaded:

lsmod | grep kvm

You should see kvm_intel (for Intel) or kvm_amd (for AMD) listed. If not, load the appropriate module:

sudo modprobe kvm_intel  # For Intel
sudo modprobe kvm_amd    # For AMD

4. Check the Hypervisor’s Access Permissions

Make sure the libvirt-qemu user or your system’s QEMU process has the necessary permissions to access the image:

sudo chown qemu:qemu /var/lib/libvirt/images/focal-server-cloudimg-amd64.img
sudo chmod 644 /var/lib/libvirt/images/focal-server-cloudimg-amd64.img

5. Try Running in a Direct Virtualization Mode

You can force virt-customize to use a specific backend, such as direct mode, which uses the system hypervisor (KVM):

export LIBGUESTFS_BACKEND=direct

This can help avoid the use of the libguestfs appliance, which sometimes causes issues in more restricted environments.

6. Increase the Memory Allocated to libguestfs Appliance

If the appliance is running out of memory, you can try increasing the memory allocated to it. You can do this by setting the LIBGUESTFS_MEMSIZE environment variable (e.g., 1024 MB):

export LIBGUESTFS_MEMSIZE=1024