[Libguestfs] virt-builder debian-12 --update failure

Hi, virt-builder --update debian-12 fails with: Setting up grub-pc (2.06-13+deb12u1) ... grub-pc: Running grub-install ... /dev/vda does not exist, so cannot grub-install to it! You must correct your GRUB install devices before proceeding: DEBIAN_FRONTEND=dialog dpkg --configure grub-pc dpkg --configure -a dpkg: error processing package grub-pc (--configure): installed grub-pc package post-installation script subprocess returned error exit status 1 Any idea why /dev/vda isn't available to grub-install in virt-builder? I guess there might be some special guest device configuration for the guestfs appliance that runs virt-builder steps, causing the device to appear as something other than /dev/vda. If I omit --update on the virt-builder command-line and run "dpkg-reconfigure grub-pc" inside the guest after importing with virt-install then it succeeds and /dev/vda exists. Thanks, Stefan