If your virtual machine does not shut down when asked by the hypervisor, install the package acpi-support.

sudo apt-get install acpi-support

Works at least with KVM, but I see no reason why it would not work as well in other virtualization platforms, if they just send the ACPI shutdown signal …

If you need to create lots of similar virtual machine guests running on QEMU/KVM, it is a very good idea to prepare a template guest image from which to clone the other guests. You should do whatever customizations you like before cloning. For instance I like to configure LVM …

The virt-manager VNC screen is fine for LAN connections, and good for running graphical sessions. X is not installed on Ubuntu server by default, and VNC is really bad over slow links even for text console. I like to configure serial console for all my virtualized guests, because with it …

First, some empty disk space is needed. Let's create a logical volume for our new virtual machine:

root@xenserver1:~# lvcreate -n testlv -L 10G vg0
  Logical volume "testlv" created

Create a filesystem on the new logical volume:

root@xenserver1:~# mke2fs -j /dev/vg0/testlv
mke2fs 1.40-WIP (14-Nov-2006)
Filesystem label …