Regarding this scenario I have been using lot of Ubuntu releases, but the latest (15.04 Vivid Vervet) has proven to be the most stable so far.
Anyway, to get it running (as simply as possible), proceed as following:
- install the VIvid Vervet, using the largest partition size possible
- let it check for updates (you don't even have to download them - just let it refresh its base, the cache of available packages)
- presuming that your system (primarily the CPU) supports virtualization extensions, install Libvirt, KVM / Qemu and a Virtual Machine Manager (for example - if you're prone to GUI) by issuing the following command: sudo apt-get install libvirt-bin qemu-kvm virt-manager bridge-utils (confirm the installation with "Y)
- after the instalation has finished, reboot the system (in order to create the needed directories, like /var/lib/libvirt/images etc.)
- after the reboot, run the following command (replace Name with your login name): sudo adduser Name kvm
- in order to prevent potential (please read as: very likely to happen to you also) permission problems, change the owner of the /var/lib/libvirt/images directory by running the following command: sudo chown Name /var/lib/libvirt/images and use it to store your future VM disks (storage) (that's the reason for the recommendation stated under 1)
- you can check for the basic functionality of KVM by issuing: kvm-ok
- optionally, if you still have any permission-related problems, try editing /etc/libvirt/qemu.conf (uncomment the "user = root" and "group = root" lines) - this can be done by issuing the following command: sudo gedit /etc/libvirt/qemu.conf, then pressing "Ctrl" + "F" and searching for the aforementioned lines (save the file after that)
- finally, run the Virtual Machine Manager (or other VM management tool)...