Apple NetInstall is an offshoot of the NetBoot technology built into Mac OS X Server. A NetInstall set contains the disk image that will be used for the deployment and the same boot files contained in a NetBoot set. Workstations that will be the targets of the deployment boot from the NetInstall set as they would a traditional NetBoot set. Instead of booting into Mac OS X, however, the workstations boot into the Mac OS X Installer application. The Installer then performs the deployment (with or without user interaction as indicated by the settings chosen when the NetInstall set was created on the server).
NetInstall can be used to perform a variety of types of deployments. In its most basic variation, NetInstall uses the Mac OS X Installer CDs or DVD to create an image that performs the same basic install that can be started from those disks. NetInstall can also be used to deploy a complete disk image (similar to ASR) or to deploy specific packages or files. This variety of choices makes NetInstall a very useful tool because it can be used to perform complete workstation configuration deployments (with a preconfigured operating system and installed applications) or it can be used to roll out updates of applications, packages, or configuration files.
NetInstall does require Mac OS X Server and a relatively fast network. For most situations you will also want to have at least one dedicated server for NetInstall and NetBoot. Configuring and managing NetInstall sets can be a little more confusing at first than using ASR. However, when paired with Apple Remote Desktop as a method for setting the startup disk and restarting remote workstations, NetInstall can make an easy solution for performing deployments without needing to physically touch each workstation.