2010/12/28 Patric Falinder <patric.falinder(a)omg.nu&gt;: RestrictedVersion is the relevant word here and the problem is on the server side and not in libvirt itself. I guess you're actually using an ESXi 4.0 server and it's license has expired. In that case the ESXi server is in "free" mode and it's management API (the vSphere API) can only be used in read-only mode. libvirt uses the vSphere API to manage the ESX(i) server. When the vSphere API is in read-only mode libvirt can still list guest and output information about them. It can also still define new guests and create new storage volumes, but it cannot start or reboot guests as the ESX(i) server rejects this with a RestrictedVersion fault. You can reboot a guest using the vSphere Client even in free/read-only mode because VMware designed it to be that way. A newly installed ESX(i) server comes with a 60 days full featured evaluation license that also enables full vSphere API access. After 60 days of usage the license expires and the ESX(i) server goes into free/read-only mode and the vSphere Client is the only tool that can start or reboot guest in this mode. You can find additional details in the VMware blog post: http://blogs.vmware.com/esxi/2009/06/esxi-vs-esx-a-comparison-of-features... Matthias