The first step is to prepare your VM. Basically you can use any VM. Simply install the Cloud-Init packages inside the VM that you want to prepare. On Debian/Ubuntu based systems this is as simple as:
apt-get install cloud-init
This command is not intended to be executed on the Proxmox VE host, but only inside the VM.
Already many distributions provide ready-to-use Cloud-Init images (provided as .qcow2 files), so alternatively you can simply download and import such images. For the following example, we will use the cloud image provided by Ubuntu at https://cloud-images.ubuntu.com.
# download the image wget https://cloud-images.ubuntu.com/bionic/current/bionic-server-cloudimg-amd64.img
# create a new VM with VirtIO SCSI controller qm create 9000 --memory 2048 --net0 virtio,bridge=vmbr0 --scsihw virtio-scsi-pci
# import the downloaded disk to the local-lvm storage, attaching it as a SCSI drive qm set 9000 --scsi0 local-lvm:0,import-from=/path/to/bionic-server-cloudimg-amd64.img
Ubuntu Cloud-Init images require the virtio-scsi-pci controller type for SCSI drives.
The next step is to configure a CD-ROM drive, which will be used to pass the Cloud-Init data to the VM.
qm set 9000 --ide2 local-lvm:cloudinit
To be able to boot directly from the Cloud-Init image, set the boot parameter to order=scsi0 to restrict BIOS to boot from this disk only. This will speed up booting, because VM BIOS skips the testing for a bootable CD-ROM.
qm set 9000 --boot order=scsi0
For many Cloud-Init images, it is required to configure a serial console and use it as a display. If the configuration doesn’t work for a given image however, switch back to the default display instead.
qm set 9000 --serial0 socket --vga serial0
In a last step, it is helpful to convert the VM into a template. From this template you can then quickly create linked clones. The deployment from VM templates is much faster than creating a full clone (copy).
qm template 9000
Ref:
https://pve.proxmox.com/wiki/Cloud-Init_Support
