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Nested virtualization

Linux based virtual machines (VM) support nested virtualization.

To check if nested virtualization is supported, we suggest issuing grep -cw vmx /proc/cpuinfo. The resulting number will be greater than 0 since the virtualization flag is present on all VM CPU cores.

Nested virtualization can be managed through libvirt, which is already preinstalled.

The predefined default network for nested virtualization is 192.168.123.0/24. The base VM provides virbr0 interface with the IP address: 192.168.123.1.

Here is an example of nested virtualization using uvltool and prebuilt Ubuntu cloud images:

version: v1.0
name: Demo nested virtualization
agent:
  machine:
    type: e1-standard-2
    os_image: ubuntu2004

blocks:
  - name: with uvltool
    task:
      jobs:
      - name: Using ubuntu cloud images
        commands:
          - checkout
          - sudo apt-get install -y uvtool sshpass net-tools netcat-openbsd
          - uvt-simplestreams-libvirt --verbose sync --source http://cloud-images.ubuntu.com/daily release=focal arch=amd64
          - uvt-simplestreams-libvirt query
          - rm -rf ~/.ssh/id_rsa
          - echo | ssh-keygen -t rsa  -f ~/.ssh/id_rsa
          - uvt-kvm create vm1 --memory 1024 --cpu 1 --disk 4 --password ubuntu --bridge virbr0
          - uvt-kvm list
          - IP=""
          - while [ -z $IP ];do IP=$(arp -an | grep $(virsh dumpxml vm1| grep "mac address" | cut -d"'" -f2)|cut -d"(" -f2|cut -d")" -f1);done
          - echo $IP
          - while ! nc -w5 -z $IP 22; do  echo "Sleep while $IP is up";sleep 1; done
          - sshpass -p "ubuntu" -v  ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no ubuntu@$IP -t 'uname -a'