What is the dom0?

Dom0 is the initial domain started by the Xen hypervisor on boot. Dom0 is an abbrevation of “Domain 0” (sometimes written as “domain zero” or the “host domain”).

Dom0 is a privileged domain that starts first and manages the DomU unprivileged domains. The Xen hypervisor is not usable without Dom0.

Dom0 is not the hypervisor – it is a quest VM just like the others

Modified versions of Linux, NetBSD and Solaris can be used as the dom0.

This is essentially the “host” operating system (or a “service console”, if you prefer). As a result, Dom0 runs the Xen management toolstack, and has special privileges, like being able to access the hardware directly.
Dom0 has drivers for hardware, and it provides Xen virtual disks and network access for guests each referred to as a domU (unprivileged domains). For hardware that is made available to other domains, like network interfaces and disks, it will run the BackendDriver, which multiplexes and forwards to the hardware requests from the FrontendDriver in each DomU.
Unless DriverDomain’s are being used or the hardware is passed through to the domU, the dom0 is responsible for running all of the device drivers for the hardware.

  • Brain of the system – runs the body
  • Often called ‘privileged’ or ‘control’ domain.
  • First virtual machine/domain started by Xen
  • Runs the management toolstack – xend or xl
  • Has special privileges, can access hardware directly
  • Runs the actual drivers for hardware
  • Provides access to these drivers to domU (unprivileged) domains by giving them virtual block and network devices
  • Creates a backend driver which corresponds to frontend driver in the domU
  • Not the only domain that can run the device drivers – access can be delegated to a ‘stub’ domain

http://wiki.xenproject.org/wiki/Dom0_Kernels_for_Xen

 

What is your understanding of “dom0”?

Dom0, or domain zero is the first domain started by the Xen hypervisor on boot. It has special privileges, like being able to cause new domains to start, and being able to access the hardware directly. It is responsible for running all of the device drivers for the hardware. For hardware that is made available to other domains, like network interfaces and disks, it will run the !BackendDriver, which multiplexes and forwards to the hardware requests from the !FrontendDriver in each !DomU. Domain0 Role  : Creates and manages guest VM (via xm). Interacts with the Xen hypervisor via xend. Supplies device and I/O services (runs (backend) device drivers, provides domain storage).