Mac OS X in a Nutshell

Exploring Common Directories

This section explores several important directories that most every Mac OS X machine has in its NetInfo database. For solitary Macs, these all live in the local NetInfo domain. Macs living as leaves in a more complicated tree of bound NetInfo domains might find directories at different levels of the information hierarchy. For example, a lab might have all its Macs’s local domains bound to a server domain that holds all login information in a single /Users directory.

aliases

Defines aliases used by this machine’s mail server (usually sendmail). See Chapter 13 for more about running a mail server on Mac OS X.

This directory replaces the old Unix /etc/aliases flatfile.

config

Stores miscellaneous system config information. The Date & Time preference panel, for instance, keeps the address of the selected NTP host inside this directory.

groups

Replaces the Unix /etc/groups flatfile, listing the system’s groups with their names, GIDs, and member users.

machines

Replaces /etc/hosts by assigning hostnames to machines via their IP or Ethernet (MAC) addresses. localhost is usually defined here, for example, pointing at 127.0.0.1, the network loopback address. Your computer consults the /machines directories of visible domains to find hosts that DNS can’t locate. (All this work occurs transparently to you, courtesy of the lookupd daemon.)

Domains’ /machines directories also play a special role in setting up NetInfo hierarchies, as described in the next section. ...