Re: Very basic question

[Andy Smith <andy@xxxxxxxxxxxxxx>]

Hi,

On Sat, Aug 29, 2026 at 09:54:43PM -0500, Leroy Tennison wrote:
> If xen is (or can be) a type 1 hypervisor, why do the instructions
> require installing a Linux distribution such as Debian and then
> installing the xen-system-amd64 package?

It's because Xen is only a hypervisor not a full operating system so for
management of it you need something to run the management tools from,
which by convenience could be a minimal Linux install.

Xen has a privileged guest that can manage it, this is called dom0. When
you install Debian and xen-system-amd64 you are setting up something
that boots the Xen hypervisor as its kernel and then starts that Linux
install as dom0.

In theory there is no reason why dom0 couldn't be some appliance-like
software. It is just another virtual machine with Xen management tools
installed.

> Is xen running under the distribution?

No. When you install xen-system-amd64 on Debian that puts the Xen
hypervisor kernel in /boot and sets up your boot loader to boot it. When
you reboot and select that hypervisor it's Xen that boots and  it starts
your old Debian as dom0 virtual machine. You end up with a hypervisor
and one VM running. That dom0 may then be configured to start other
unprivileged virtual machines (domUs).

Thanks,
Andy