Comment 9 for bug 1646532

Here's what <vigo_> shared with me:

To prepare an image for testing I follow these steps:

Create an image for a xenial + stable-overlay ppa + unity8-desktop-session:
$ qemu-img create -f qcow2 kvm-images/xenial-base.qcow2 30G

Run a xenial image in qemu and install it in the new image created:
$ kvm -m 2048 -vga qxl -cpu host --soundhw ac97 -cdrom ~/Downloads/ubuntu-16.04.1-desktop-amd64.iso -hda kvm-images/xenial-base.qcow2 -boot c

Once installed we should install both stable-overlay and unity8-desktop-session:
$ sudo add-apt-repository ppa:ci-train-ppa-service/stable-phone-overlay
$ sudo apt-get update
---
$ sudo apt install unity8-desktop-session

Now reboot to check that unity8 is available to login and verify it works properly.

I run an image like the one described with the -snapshot argument on kvm-qemu to test silos in xenial+overlay. Rebooting is possible within the VM so you can install silos or whatever you need for testing, and stop the VM when you’re done, this way the based image for xenial+overlay remains clean.

Is also a good practice to run the image without the snapshot argument in order to update your base image