vu

vu (virtual machin up) is a CLI tool which lets you spin up virtual machines quickly. Its goal is to spin up a new VM and connect to it via SSH without going through a cumbersome install wizard and without maintaining special VM images which support automatic installation ourselves. To achieve this vu relies on VM images which contain cloud-init. Cloud-init runs during the first boot, reads the configuration from a datasource and then configures the VM accordingly (user, network, etc.). The datasource is usually provided by a cloud provider. To use the cloud-init images locally we make use of the NoCloud datasource where we provide the configuration as an attached CDROM.

vu usually does the following steps to start a VM:

• Create a cloud-init config (user data, metadata, network configuration) based on the local user (username, ssh key)
• Create an ISO image with the cloud-init config in it
• Clone an image for the new VM from a base image (see https://libvirt.org/kbase/backing_chains.html)
• Start a VM with cloned image and the the ISO image attached as CDROM

Quick start

• Install libvirtd

# on Ubuntu
sudo apt install libvirt-daemon-system
sudo adduser $USER libvirt

• Install vu under ~/bin

curl -L -o ~/bin/vu https://github.com/dvob/vu/releases/download/v0.0.4/vu_linux_amd64 && chmod +x ~/bin/vu

• Run a VM

# get  a base image
vu image add https://cloud-images.ubuntu.com/minimal/daily/focal/current/focal-minimal-cloudimg-amd64.img

# create and start a new VM
vu create focal-minimal-cloudimg-amd64.img mytest1

# list the VMs
vu list

To connect to the VM it is recommended to install the Libvirt NSS module and configure it accordingly:

# on Ubuntu
sudo apt-get install libnss-libvirt

/etc/nsswitch.conf:

# ...
hosts:    files libvirt dns
# ...

Then you can simply connect to server like this:

ssh mytest1

If you don't want to use the Libvirt NSS module or you specified a static IP on create with --ip then you have to use the IP to connect to the VM.

Images

To find base images you can search for cloud init images and then look out for images in the qcow2 format. Usually they have the .img or .qcow2 file ending. The following link provides a good overview on where you can find cloud-init images: https://docs.openstack.org/image-guide/obtain-images.html

If you have found an appropriate image you can download it (add it to the base images) with vu image add. I tested vu with the following images:

# add ubuntu image
vu image add https://cloud-images.ubuntu.com/daily/server/bionic/current/bionic-server-cloudimg-amd64.img
vu image add https://cloud-images.ubuntu.com/minimal/daily/focal/current/focal-minimal-cloudimg-amd64.img

# rocky linux image
vu image add https://download.rockylinux.org/pub/rocky/8.5/images/Rocky-8-GenericCloud-8.5-20211114.2.x86_64.qcow2

# with rocky 8.6 the image does not contain sudo and you have to enhance the base configuration as follows
mkdir -p ~/.vu/sudo
cat <<EOF > ~/.vu/sudo/user-data
{
  "packages": ["sudo"]
}
EOF
vu create --dir ~/.vu/sudo Rocky-8-GenericCloud-8.6-20220515.x86_64.qcow2 rocky

# add centos image
vu image add https://cloud.centos.org/centos/8/x86_64/images/CentOS-8-GenericCloud-8.3.2011-20201204.2.x86_64.qcow2

# add debian image
vu image add http://cdimage.debian.org/cdimage/openstack/current/debian-10-openstack-amd64.qcow2

Storage location

vu uses three storage pools to store the images:

• base for base images
• vm for vm instances
• config for config ISOs (cidata for cloudinit)

If these storage pools do not yet exist vu creates them on the fly as directory pool under /var/lib/libvirt/images/vu/{base,config,vm}.

Shell completion

source <( vu completion bash )