N00B Q: Troubleshooting headless Ubuntu install on RHEL 7.8 w/ qemu/kvm

I have been successfully building images based on Ubuntu 18.04, with and without console displays, with Packer on macOS. Now I need to retarget for a RHEL 7.8 server using qemu/kvm as the virtualization platform.

I am able to build a VM with virt-install - as long as I have a console display. I have not had any success building headless, either with virt-install or Packer. If I set headless to false in the Packer configuration, I get a message saying “The version of qemu on your host doesn’t support display mode.”

How can I track the progress of a headless build? What are some n00b mistakes I might be making in configuring it?

Thanks for any pointers.

[ETA:] Packer 1.6.0, qemu reports version 1.5.3. RHEL 7.8 on a brand new Dell server.

I was successful in getting a VNC viewer connected. The installer is reporting “No root file system”, and attempts to correct this manually are not successful. The ‘Detect Disks’ step is failing.

Packer has created the disk image via qemu-img with format ‘raw’, and the Ubuntu installer is not detecting it for some reason. How can I find the device node for the disk image? How can I tell Packer what device node to assign it in the qemu command line?

It appears the disk image is attached at /dev/vda, which makes sense, but wasn’t documented anywhere that I can detect. I think I’m on my way.