Open Directory, lookupd, and NetInfo

C H A P T E R 1

Concepts

Directory function that requires such a reference. Once a remote Open Directory session is successfully opened, Open Directory automatically sends all calls to Open Directory functions that use the remote directory reference to the DirectoryService daemon over the encrypted TCP/IP connection. Other than calling dsOpenDirServiceProxy, there is nothing the application has to do in order for its actions to take effect on the remote system.

The process lookupd can be used to look up various categories of data, typically configuration information, such as users, groups, networks, services, protocols, remote procedure calls, (RPC), mounts, printers, boot parameters, aliases and netgroups, but also DNS information. This section describes how Open Directory works with lookupd and NetInfo.

The lookupd process works through the use of agents, with each agent designed to obtain a particular type of information. For example, there is an agent for resolving DNS queries, an agent for querying the local NetInfo database and its parents, and agent for querying LDAP directories, an agent for querying the Network Information System (NIS), and an agent for querying UNIX flat files in the file system. There is also an agent for querying the lookupd cache, in which lookupd stores information that has recently been looked up. The agents and the order in which the agents are used to look up information are configured through command-line utilities. By default, the lookupd cache is searched first, followed by NetInfo, and then Open Directory.

Like lookupd, Open Directory has a flexible architecture, provided by Open Directory plug-ins, for finding a wide variety of information. Unlike lookupd, Open Directory is configured by the graphical tool, Directory Access. While UNIX-based programs use lookupd to get information from external sources, Mac OS X applications use Open Directory.

The lookupd process can be configured to work with Open Directory through the use of the DSAgent. When a process that uses lookupd requires a piece of information, lookupd searches its cache and any other configured agents. If no results are found, the DSAgent queries Open Directory. Take, for example, the searching that occurs when “tjones” logs in using SSH, as shown in Figure 1-3(page 23). In this example, the lookupd cache is searched first. The user “tjones” is not in the cache, so lookupd queries NetInfo, which finds “tjones” in the local NetInfo database (local.nidb). Open Directory does not participate in this particular login process.

22Open Directory, lookupd, and NetInfo