CHEF Bento issue when build a vagrant box with qemu & multi-disks

Hello all,
As I started to learn CHEF, to install 'Chef Workstation' on my Virtual env, I discover Chef/Bento which help me to easily build VM from scratch following my customization rules :slightly_smiling_face:.
I started with success with Virtual box but I would also try KVM/QEMU.
To imitate VM design of my company, I would just like to keep a boot disk with mainly the OS matters and a second one with all other middle-ware and data.
As 'packer' already foreseen this 'disk_additional_size' option for this kind of purpose, I just ad very few line to add a variable def:

variable "qemu_disk_additional_size" {
  type    = list(string)
  default = null

to enhance the source def of qemu vm:

source "qemu" "vm" {
  # QEMU specific options
  disk_size        = var.disk_size
  disk_additional_size = var.qemu_disk_additional_size == null ? [] : var.qemu_disk_additional_size
  floppy_files     = local.floppy_files

and add requirement in my box setup:

qemu_disk_additional_size = [ "69632M" ]
#qemu_disk_additional_size = [ "68G" ]

(i.e. the same kind of tips to build successfully a custom vbox :blush:)

'packer' create well the qemu vm with the 2 requested disks.
(as it's a 15min procees I can access the system and check:

Filesystem                        Size  Used Avail Use% Mounted on
devtmpfs                          968M     0  968M   0% /dev
tmpfs                             997M  4.0K  997M   1% /dev/shm
tmpfs                             997M   17M  981M   2% /run
tmpfs                             997M     0  997M   0% /sys/fs/cgroup
/dev/sr0                          988M  988M     0 100% /run/install/repo
/dev/mapper/live-rw               2.0G  1.6G  386M  81% /
tmpfs                             997M  892K  997M   1% /tmp
/dev/mapper/rootvg-root           8.0G  802M  7.3G  10% /mnt/sysimage
/dev/mapper/localvg-house_apps       509M   26M  483M   6% /mnt/sysimage/house_apps
/dev/mapper/localvg-house_apps_data  509M   26M  483M   6% /mnt/sysimage/house_apps_data
/dev/vda2                         2.0G   43M  2.0G   3% /mnt/sysimage/boot
/dev/vda1                        1022M   12K 1022M   1% /mnt/sysimage/boot/efi
tmpfs                             997M     0  997M   0% /mnt/sysimage/dev/shm
/dev/mapper/rootvg-home           2.0G   33M  2.0G   2% /mnt/sysimage/home
/dev/mapper/rootvg-opt            2.0G   33M  2.0G   2% /mnt/sysimage/opt
/dev/mapper/localvg-bakups           1.5G   33M  1.5G   3% /mnt/sysimage/opt/mdwr/bakups
/dev/mapper/localvg-sys_house_apps   509M   26M  483M   6% /mnt/sysimage/sys_house_apps
/dev/mapper/localvg-security     1014M   33M  982M   4% /mnt/sysimage/sys_house_apps/security
/dev/mapper/localvg-moneymaker       1014M   33M  982M   4% /mnt/sysimage/sys_house_apps/moneymaker
/dev/mapper/localvg-mdwr        4.0G   33M  4.0G   1% /mnt/sysimage/sys_house_apps/mdwr
/dev/mapper/rootvg-tmp            2.0G   33M  2.0G   2% /mnt/sysimage/tmp
/dev/mapper/rootvg-stage_area    4.0G   33M  4.0G   1% /mnt/sysimage/stage_area
/dev/mapper/rootvg-var            4.0G  128M  3.9G   4% /mnt/sysimage/var
/dev/mapper/rootvg-syslogs        4.0G   33M  4.0G   1% /mnt/sysimage/var/log

but at the end:

oskvm (pts14)jlst@oskvm:/Extra/vguest_img/IMGs02/Vagrant/osxfce_bento-rudy |\
$ packer build -force -on-error=ask -only=qemu.vm -var-file=os_pkrvars/centos/rudy-UTS-centos7-efi-x86_64.pkrvars.hcl ./packer_templates
==> qemu.vm: Provisioning with shell script: ./packer_templates/scripts/_common/
==> qemu.vm: + case "$PACKER_BUILDER_TYPE" in
==> qemu.vm: + exit 0
==> qemu.vm: Gracefully halting virtual machine...
==> qemu.vm: Converting hard drive...
==> qemu.vm: Running post-processor:  (type vagrant)
==> qemu.vm (vagrant): Creating a dummy Vagrant box to ensure the host system can create one correctly
==> qemu.vm (vagrant): Creating Vagrant box for 'libvirt' provider
    qemu.vm (vagrant): Copying from artifact: builds/packer-centos-7.9-x86_64-qemu/centos-7.9-amd64
    qemu.vm (vagrant): Compressing: Vagrantfile
    qemu.vm (vagrant): Compressing: box.img
    qemu.vm (vagrant): Compressing: metadata.json
Build 'qemu.vm' finished after 13 minutes 58 seconds.

==> Wait completed after 13 minutes 58 seconds

==> Builds finished. The artifacts of successful builds are:
--> qemu.vm: 'libvirt' provider box: ./packer_templates/../builds/

i.e. only the first disk is set in the 'box'

oskvm (pts14)jlst@oskvm:/Extra/vguest_img/IMGs02/Vagrant/osxfce_bento-rudy |\
$ ls -lh ./builds/
-rw-r--r-- 1 jlst sysadmin 583M Aug 23 10:08 ./builds/

oskvm (pts14)jlst@oskvm:/Extra/vguest_img/IMGs02/Vagrant/osxfce_bento-rudy |\
$ tar -tslpvf ./builds/
-rw-r--r-- jlst/sysadmin   296 2023-08-23 10:07 Vagrantfile
-rw-r--r-- jlst/sysadmin 1403584512 2023-08-23 10:07 box.img
-rw-r--r-- jlst/sysadmin         58 2023-08-23 10:07 metadata.json

oskvm (pts14)jlst@oskvm:/Extra/vguest_img/IMGs02/Vagrant/osxfce_bento-rudy |\
$ tar -xslpvf ./builds/ Vagrantfile

oskvm (pts14)jlst@oskvm:/Extra/vguest_img/IMGs02/Vagrant/osxfce_bento-rudy |\
$ cat Vagrantfile

# The contents below were provided by the Packer Vagrant post-processor

Vagrant.configure("2") do |config|
  config.vm.provider :libvirt do |libvirt|
    libvirt.driver = "kvm"

# The contents below (if any) are custom contents provided by the
# Packer template during image build.

on the contrary of Virtualbox:

==> virtualbox-iso.vm (vagrant): Creating a dummy Vagrant box to ensure the host system can create one correctly
==> virtualbox-iso.vm (vagrant): Creating Vagrant box for 'virtualbox' provider
    virtualbox-iso.vm (vagrant): Copying from artifact: builds/packer-centos-7.9-x86_64-virtualbox/centos-7.9-amd64-disk001.vmdk
    virtualbox-iso.vm (vagrant): Copying from artifact: builds/packer-centos-7.9-x86_64-virtualbox/centos-7.9-amd64-disk002.vmdk
    virtualbox-iso.vm (vagrant): Copying from artifact: builds/packer-centos-7.9-x86_64-virtualbox/centos-7.9-amd64.ovf
    virtualbox-iso.vm (vagrant): Renaming the OVF to box.ovf...
    virtualbox-iso.vm (vagrant): Compressing: Vagrantfile
    virtualbox-iso.vm (vagrant): Compressing: box.ovf
    virtualbox-iso.vm (vagrant): Compressing: centos-7.9-amd64-disk001.vmdk
    virtualbox-iso.vm (vagrant): Compressing: centos-7.9-amd64-disk002.vmdk
    virtualbox-iso.vm (vagrant): Compressing: metadata.json
Build 'virtualbox-iso.vm' finished after 6 minutes 33 seconds.

==> Wait completed after 6 minutes 33 seconds

==> Builds finished. The artifacts of successful builds are:
--> virtualbox-iso.vm: 'virtualbox' provider box: ./packer_templates/../builds/
osxfce154 (pts89)jlst@osxfce154:/Extra/Vagrant.d/jlst/Develop/Vagrant/bento-rudy |\
$ ls -l ./builds/
osxfce154 (pts89)jlst@osxfce154:/Extra/Vagrant.d/jlst/Develop/Vagrant/bento-rudy |\
$ ls -l ./builds/
-rw-r--r-- 1 jlst sysadmins 689407205 Aug 20 12:22 ./builds/

Any idea where should I start to investigate : bento, vagrant, packer, ...?

Tia for further advises,

I'd start by looking at packer and the qemu plugin. Bento is taking default packer Vagrantfile created by packer and the provider plugin. GitHub - hashicorp/packer-plugin-qemu: Packer plugin for QEMU Builder

Ok (I will put it temporarily on hold: time to me learning basics of GO :wink:)
Thx again & take care