Management Domain (dom0)

Most of the responsibility of hardware detection in an Oracle VM Server environment is passed to the management domain, referred to as domain zero (or dom0). On x86-based servers, the dom0 kernel is actually a small-footprint Linux kernel with support for a broad array of devices and file systems. In Oracle VM Server, the dom0 is tasked with providing a view of the system hardware available to the hypervisor. It also allows you to interact directly with the hypervisor to control access to resources as well as performing various tasks such as creating, destroying and controlling guest operating systems, and presenting those guests with a set of common virtual hardware. Other domains never interact with dom0 directly. Their requirements are handled by the hypervisor itself. Dom0 only provides a means to administer the hypervisor.

On SPARC-based servers, the management domain, usually referred to as the primary service domain or control domain, is created when the logical domains manager is installed. If installed on an existing server that is not already configured for logical domains, the current Operating System automatically gets promoted to primary domain status. The primary domain runs an Oracle Solaris kernel and is responsible for the creation and management of all other domains. It is also responsible for providing access to virtualized hardware resources.

On systems running Oracle VM Server for SPARC, aside from the concepts of a "management domain" and of "guest domains", similar to "user domains", there are a variety of other domain-types that can run alongside the management domain. For instance, it is possible to set up multiple "service domains" that can act as network switches and virtual disk servers. Not all of these domain types are configurable using the Oracle VM Manager. Most importantly, it is possible to add a secondary service domain to your servers that can take over disk and network I/O in the case where the primary domain must be restarted. This allows running guest virtual machines to continue to access these resources even while the primary domain is unavailable. This topic is discussed in more detail within Configuring a Secondary Service Domain on SPARC in the Oracle VM Administrator's Guide.

Supported Operations in the Management Domain (dom0)

Oracle VM Manager allows you to manage and configure your virtualization infrastructure, including the dom0. Manually modifying the dom0 can result in configuration issues for either Oracle VM Manager or Oracle VM Server, which can degrade performance or cause a loss of service. For this reason, Oracle does not support any changes that are made to the dom0 outside of Oracle VM Manager. Likewise, Oracle does not support running any third party applications within the dom0.

In general, you should not perform any operations that modify the dom0 configuration. The following are examples of operations that you can perform on the dom0:

If you are in doubt whether an operation on the dom0 is supported, contact Oracle Support.