Create a hypervisor virtual machine on the host

Build on the L1 guest VM setup

You’ve used command line tools to create, boot, and connect to a guest virtual machine (VM) running on your Arm64 host. After completing the steps, you’ll have another VM running on the host that can serve as a hypervisor for nested VMs.

Prepare and resize the L1 hypervisor disk image

Set similar convenience environment variables to the L1 guest VM. The L1 hypervisor needs a bigger disk than the L1 guest, because it contains an identical 40GB L2 guest image inside it:

    

        
        
# If these environment variables are already set, there is no need to re-set them
export VMDIR="/var/lib/libvirt/images"
export IMG="${HOME}/Fedora-Cloud-Base-Generic-44-1.7.aarch64.qcow2"

# Use a different QCOW2 filename for the hypervisor VM
export DISK_L1_HYPER="${VMDIR}/fedora-l1-hyper.qcow2"

# Prepare the L1 hypervisor image
sudo cp "$IMG" "$DISK_L1_HYPER"
sudo qemu-img resize "$DISK_L1_HYPER" 80G

    

Create a cloud-init seed ISO

Create a seed ISO image for the guest hypervisor for cloud-init. Replace <your-public-key> with the same public SSH key that you used for the L1 guest VM:

    

        
        
 cat > /tmp/user-data <<EOF 
 #cloud-config 
 users: 
  - name: fedora 
    sudo: ALL=(ALL) NOPASSWD:ALL 
    shell: /bin/bash 
    ssh_authorized_keys: 
      - <your-public-key> 
 chpasswd: 
   expire: False 
 ssh_pwauth: False 
 EOF 

 cat > /tmp/meta-data <<EOF 
 instance-id: my-hyper 
 local-hostname: my-hyper 
 EOF 

 SEEDTMP=$(mktemp -d) 
 cp /tmp/user-data "$SEEDTMP/user-data" 
 cp /tmp/meta-data "$SEEDTMP/meta-data" 
 genisoimage -output ${HOME}/seed_hyper.iso \
      -volid cidata -joliet -rock -input-charset utf-8 \
      "$SEEDTMP/user-data" "$SEEDTMP/meta-data"
 sudo cp ${HOME}/seed_hyper.iso ${VMDIR} 
 rm -rf "$SEEDTMP" 

    

The main change here is the hostname my-hyper.

Start the L1 hypervisor VM

Start the L1 hypervisor VM using virt-install:

    

        
        
 sudo virt-install \
   --name fedora-l1-hyper \
   --memory 8192 \
   --vcpus 16 \
   --arch aarch64 \
   --machine virt \
   --disk path=${DISK_L1_HYPER},format=qcow2,bus=virtio \
   --disk path=${VMDIR}/seed_hyper.iso,device=cdrom,readonly=on \
   --network network=default,model=virtio \
   --os-variant fedora43 \
   --import \
   --noautoconsole

    

Shut down the VM to edit its configuration

After the VM starts and obtains an IP address, shut it down to make some changes to the XML that defines the VM:

    

        
        
 # Check that the VM is fully initialized first
 sudo virsh net-dhcp-leases default 

 # After this command shows that the VM has an IP address, proceed
 sudo virsh shutdown fedora-l1-hyper 
 sudo virsh list --all # Verify that VM status is "shut off" 

    

Enable virtualization in the VM configuration

You’ll pass a kernel parameter to the VM that enables passthrough of virtualization capability. This turns the VM into a hypervisor.

Open the VM configuration in an editor:

    

        
        
sudo virsh edit fedora-l1-hyper

    

Edit the XML configuration that describes the VM to make two changes. First, import the XML schema for the qemu namespace, which lets you pass additional parameters to the qemu command that instantiates the VM.

Change the opening <domain> tag to import the qemu namespace schema:

    

        
        
<domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>

    

Second, add a <qemu:commandline> block that enables virtualization functionality.

Just before the closing </domain> tag, add the following block:

    

        
        
<qemu:commandline>
  <qemu:arg value='-machine'/>
  <qemu:arg value='virt,virtualization=on'/>
</qemu:commandline>

    

Save the file. virsh validates the XML against the libvirt schema when you save.

Boot the hypervisor VM and verify virtualization support

Boot the L1 hypervisor VM and verify that virtualization is supported:

    

        
        
 sudo virsh start fedora-l1-hyper
 # After a few seconds...
 sudo virsh net-dhcp-leases default
 ssh -i ~/.ssh/guest_key fedora@{ip address}

    

Inside the fedora-l1-hyper VM, verify that virtualization functionality has been passed through:

    

        
        
sudo dmesg | grep -i "el2\|vhe\|kvm"

    

The output is similar to:

    

        
        CPU: All CPU(s) started at EL2
kvm [1]: VHE mode initialized successfully

        
    

Confirm that /dev/kvm exists inside the VM:

    

        
        
ls -la /dev/kvm

    

If you see the line CPU: All CPU(s) started at EL2, you now have a VM that can function as a hypervisor.

What you’ve accomplished and what’s next

You’ve now created an L1 hypervisor VM and booted it.

Next, you’ll install virtualization tooling and instantiate an L2 guest VM inside the hypervisor.