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TITLE
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TOPIC
This article is a brief introduction to NetInfo domains. It introduces new terms and the structure of the hierarchy.
DISCUSSION
Introduction
A NetInfo domain is a hierarchical collection of NetInfo database(s) that provide system resources and network administrative information. This article discusses a three level domain hierarchy because it is the most common. The number of levels in the hierarchy is unlimited, but it is rare that more than three are needed. Below is of graphic a what a three-level domain may look like.
Every computer that uses NetInfo has a local domain and a local database that is a repository of information that pertains specifically to that computer. The level above the local domain is usually called the network domain or network database and is a repository of shared system resources and administrative data. The next level is the root domain or root database and it is the repository of shared information for the entire network. So, each level of the domain has a corresponding database.
Processes
Also, each domain has its own server process that controls the domain. This process is called netinfod. When this process is viewed in ProcessViewer, and the Path & Arguments tab is selected, the domain the process serves is listed. On most computers it says netinfod local (master). If the computer is also a server for network domains it has processes for those. The computer serving /eng in the graphic has a netinfod local and a netinfod network process running.
Tags
Through out this article the terms local database and network database have been used. These are the tags (names) of the database. The local database tag is always "local" and the domain above the local domain is usually "network" (this is only by convention). The root database's tag is usually given a name that makes it easily identifiable, a school name, or business name. In this article the root domain's tag is Computers. A database tag is important when the hierarchy is being managed with NetInfoManager and command line utilities such as niutil.
Searching the Hierarchy
Before searching is covered a few more new terms are needed. The root domain is the parent domain for the entire network. The /eng and /mktg domains are the children of the root domain and the local domains are its grandchildren . Consequently, the /eng and /mkgt domains are parents for the local domains below.
When an application needs information it starts by searching the local NetInfo domain by contacting the netinfod for the local domain and the database is searched for the information. If the information is not the local database the parent netinfod process is contacted and its database is searched. This continues until the information is found and returned to the application or until the root domain is searched an no information is found. Thus domains at the same level are isolated.
In closing, domains are fundamental when constructing a NetInfo network. The domain structure can easily be made to mirror a company's internal structure keeping departments separate for security reasons, or they can mirror the company's physical layout such as regions, states, buildings and floors. Planning a domain map should be the first step of creating a NetInfo network.