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🗲 spawn Cloud instances on libvirt!🗲

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You want to spawn local VM quickly.. Like... really quickly. You want them to be as generical as possible. Actually you would like to reuse some existing cloud images!

This is the right tool for you.

Virt-Lightning exposes a CLI inspired by the Cloud and Vagrant. It can also prepare the Ansible inventory file.

This is handy to quickly validate a new Ansible playbook, or a role on a large number of environments.

example: less than 30 seconds to spawn an instance

In a nutshell:

echo "- distro: centos-7" > virt-lightning.yaml
vl up
vl ansible_inventory > inventory
ansible all -m ping -i inventory

example: or 75 seconds for 10 nodes lab

During this recording, we:

  1. use the list of distribution to generate a virt-lightning.yaml file.
  2. we then create a environment based on this file
  3. once the environment is ready, we generate an Ansible inventory file
  4. and we use it to call Ansible's ping module on all the host.

demo

Pre-requirements

  • The Python3 binding for libvirt, the package is probably called python3-libvirt.
  • You make also want to install python3-urwid if you want to get the fancy list of VM. This dependency is optional.
  • Libvirt must be running, most of the time you just need to run: sudo systemctl start --now libvirtd
  • Finally, be sure your user can access the system libvirt daemon, e.g with: virsh -c qemu:///system

Installation

pip3 install --user virt-lightning

If you use Ubuntu, you will need the --no-deps argument (See: https://github.com/pypa/pip/issues/4222).

virt-lightning will be installed in ~/.local/bin/. Add it in your $PATH if it's not already the case. For instance if you use:

echo "export PATH=$PATH:~/.local/bin/" >> ~/.bashrc
source ~/.bashrc

Fetch some images

Before you start your first VM, you need to fetch the images. To do so, you just use the vl fetch command:

$ vl fetch fedora-32

Actions

vl is an alias for virt-lightning, you can us both. In the rest of the document we use the shortest version.

vl distro_list

List the distro images that can be used. Its output is compatible with vl up. You can initialize a new configuration with: vl distro_list > virt-lightning.yaml.

vl up

virt-lightning will read the virt-lightning.yaml file from the current directory and prepare the associated VM.

vl down

Destroy all the VM managed by Virt-Lightning.

vl start

Start a specific VM, without reading the virt-lightning.yaml file.

vl stop

Stop just one VM.

vl status

List the VM, their IP and if they are reachable.

vl ansible_inventory

Export an inventory in the Ansible format.

vl ssh

Show up a menu to select a host and open a ssh connection.

vl ssh

vl console

Like vl ssh but with the serial console of the VM.

vl ssh

vl viewer

Like vl console but with the SPICE console of the VM. Requires virt-viewer.

vl fetch

Fetch a VM image. You can find here a list of the available images. You can also update the custom configuration to add a private image hub.

Configuration

Global configuration

If ~/.config/virt-lightning/config.ini exists, Virt-Lightning will read its configuration there.

[main]
network_name = virt-lightning
root_password = root
storage_pool = virt-lightning
network_auto_clean_up = True

network_name: if you want to use an alternative libvirt network

root_password: the root password

storage_pool: if you want to use an alternative libvirt storage pool

network_auto_clean_up: if you want to automatically remove a network when running virt-lightning down

private_hub: if you need to set additional url from where images should be retrieved, update the configuration file ~/.config/virt-lightning/config.ini adding the following

[main]
private_hub=url1,url2

VM configuration keys

A VM can be tuned at two different places with the following keys:

  • distro: the name of the base distro image to use, it's the only mandatory parameter.
  • name: the VM name
  • memory: the amount of memory to dedicate to the VM
  • root_disk_size: the size of the root disk in GB
  • vcpus: the number of vcpu to dedicate to the VM
  • root_password: the root password in clear text
  • groups: this list of groups will be used if you generate an Ansible inventory.
  • networks: a list of network to attach to the VM. The default is: one virtio interface attached to virt-lightning network.
    • network: the name of the network. Default is the key network_name from the configuration (virt-lightning by default)
    • ipv4: a static IPv4. Default is a dynamic IPv4 address.
    • nic_model: the libvirt driver to use. Default is virtio

Example: a virt-lightning.yaml file:

- name: esxi-vcenter
  distro: esxi-6.7
  memory: 12000
  root_disk_size: 30
  vcpus: 2
  root_password: '!234AaAa56'
  groups: ['all_esxi']
- name: esxi1
  distro: esxi-6.7
  memory: 4096
  vcpus: 1
  root_password: '!234AaAa56'
  groups: ['all_esxi', 'esxi_lab']
- name: esxi2
  distro: esxi-6.7
  memory: 4096
  vcpus: 1
  root_password: '!234AaAa56'
  groups: ['all_esxi', 'esxi_lab']
- name: centos-7
  distro: centos-7
  networks:
    - network: default
      ipv4: 192.168.122.50
  bootcmd:
    - yum update -y

You can also associate some parameters to the distro image itself

cat /var/lib/virt-lightning/pool/upstream/esxi-6.7.yaml
username: root
python_interpreter: /bin/python
memory: 4096
networks:
  - network: virt-lightning
    nic_model: virtio
  - network: default
    nic_model: e1000