Thank you for replying, I'm familiar with virt-sysprep/virt-customze and I want to systematically update packages of a fresh empty qcow2 image when making a template. Ovirt already allows  to use virt-sysprep thanks to seal object. I finally found the py script that deals with virt-sysprep: /usr/lib/python3.6/site-packages/vdsm/virtsysprep.py from vdsm.virt.utils import LibguestfsCommand _VIRTSYSPREP = LibguestfsCommand("virt-sysprep",                                  "/usr/bin/virt-sysprep") def sysprep(vm_id, vol_paths):     """     Run virt-sysprep on the list of volumes     :param vol_paths: list of volume paths     """     args = ['--network', '--update']     for vol_path in vol_paths:         args.extend(('-a', vol_path))     _VIRTSYSPREP.run(args, log_tag=vm_id) Default script has no argument and just seal the vm, I simply added     args = ['--network', '--update'] to update package. This modification implies to modify the script on all hosts and restart vdsmd, and is not persistent on vdsm/node upgrade. So I wondered if there was a way to make it persistent thanks to hooks. Le 16/11/2021 à 13:25, Marcos Sungaila a écrit : -- Nathanaël Blanchet Supervision réseau SIRE 227 avenue Professeur-Jean-Louis-Viala 34193 MONTPELLIER CEDEX 5 Tél. 33 (0)4 67 54 84 55 Fax 33 (0)4 67 54 84 14 blanchet(a)abes.fr