Overview of the vSphere Guest API

The vSphere Guest API provides functions that management agents and other software can use to collect data about the state and performance of a VMware virtual machine. The Guest API provides fast access to resource management information, without the need for authentication.

The Guest API provides read-only access. You can read data using the API, but you cannot send control commands. To issue control commands, use the vSphere Web Services SDK. For more information, see the VMware vSphere Web Services SDK Programming Guide and the VMware vSphere API Reference, which are available on the VMware developer support Web site.

The version number of this Guest API release is 9.0 to match the version number of VMware Tools.

Supported Guest Operating Systems

The vSphere Guest API software runs on most Windows or Linux guest operating systems supported under ESX/ESXi 4.0, ESX/ESXi 4.1, ESXi 5.0, and ESXi 5.1.

See the Guest Operating System Installation Guide for a list of supported guest operating system versions. This guide is now at http://partnerweb.vmware.com/GOSIG/home.html in Web format.

The Guest API does not support the following guest operating system environments:

■	Windows 95 and Windows 98.

■	Windows NT 4.0. For Windows NT 4.0 you must use Guest SDK 3.5, which you can find by going to http://www.vmware.com/support/developer/guest-sdk and selecting an old release.

Virtual Machine Statistics

With the Guest API, you can monitor various statistics about the virtual machine. You can use this information to retrieve scheduling and resource usage information about the environment. With the help of these statistics, a virtual machine can immediately react to changes in its virtual environment at the application layer.

The following list shows some of the information that you can retrieve through the vSphere Guest API:

■	Amount of memory reserved for the virtual machine.

■	Amount of memory being used by the virtual machine.

■	Upper limit of memory available to the virtual machine.

■	Number of memory shares assigned to the virtual machine.

■	Maximum speed to which the virtual machine’s CPU is limited.

■	Reserved rate at which the virtual machine is allowed to execute. An idling virtual machine might consume CPU cycles at a much lower rate.

■	Number of CPU shares assigned to the virtual machine.

■	Elapsed time since the virtual machine was last powered on or reset.

■	CPU time consumed by a particular virtual machine. When combined with other measurements, you can estimate how fast the virtual machine’s CPUs are running compared to the host CPUs.

Important The API uses a handle that provides access to the statistics. The handle also is a mechanism to determine whether the API can provide accurate information. (Certain events, such a migrating a virtual machine with VMotion™, temporarily make it impossible to provide accurate information.)