1. Grab a minimal distribution ISO image and download it to your oVirt ISO domain

CentOS 7: CentOS-7-x86_64-Minimal-.....iso) from http://isoredirect.centos.org/centos/7/isos/x86_64/

Ubuntu: mini.iso from http://cdimage.ubuntu.com/netboot/

2. Create a virtual machine (512MB RAM is enough at first) and boot it from the downloaded ISO image

Don't forget to assign a network interface (and a IP address or a working DHCP server).

3. Install the OS normally and reboot the VM

4. Install oVirt and Spice packages

CentOS 7:

sudo yum install 

Ubuntu:

sudo apt-get install ovirt-guest-agent spice-vdagent
chown ovirtagent /var/log/ovirt-guest-agent # fix for ubuntu 16.04
systemctl enable ovirt-guest-agent && systemctl restart ovirt-guest-agent

5. You can install a minimal graphical environment (not recommended unless you have to).

You also need to install the qxl xord driver.

Ubuntu LXDE:

sudo apt-get install lubuntu-core policykit-desktop-privileges policykit-1 lxsession-default-apps --no-install-recommends
sudo apt-get install file-roller lxrandr synaptic lxterminal leafpad --no-install-recommends
sudo apt-get install xserver-xorg-video-qxl --no-install-recommends

CentOS classic Gnome (TODO)

6. Reboot and check the results

If ovirt-guest-agent is not running (and it should be), then file permissions on /usr/share/ovirt-guest-agent/ovirt-guest-agent.py may be wrong (at least they were set incorrectly on Ubuntu 15.10).

7. After fixing the bugs have a look at the oVirt Engine Web Admin interface and check if ovirt agent is working as expected.