Mac OS X: An Introduction for Support Providers
Course Information
Purpose of Course
Mac OS X is the next-generation Macintosh operating system, utilizing a highly robust
UNIX core with a brand new simplified user experience. It is the first successful attempt
to provide a fully-functional graphical user experience in such an implementation without
requiring the user to know or understand UNIX.
This course is designed to provide a theoretical foundation for support providers seeking
to provide user support for Mac OS X. It assumes the student has performed this role for
Mac OS 9, and seeks to ground the student in Mac OS X using Mac OS 9 terms andconcepts.
Author: Robert Dorsett, manager, AppleCare Product Training & Readiness.
Module Length: 2 hours
Audience: Phone support, Apple Solutions Experts, Service Providers.
Prerequisites: Experience supporting Mac OS 9
Course map:
Operating Systems 101
Mac OS 9 and Cooperative Multitasking
Mac OS X: Pre-emptive Multitasking and Protected Memory.
Mac OS X: Symmetric Multiprocessing
Components of Mac OS X
The Layered Approach
DarwinCore Services
Graphics Services
Application Environments
Aqua
Useful Mac OS X Jargon
Bundles
Frameworks
Umbrella Frameworks
Mac OS X Installation
Initialization Options
Installation Options
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Startup Keys
Mac OS X Setup Assistant
Mac OS 9 and Classic
Standard Directory Names
Quick Answers: Where do my __________ go?
More Directory Names
A Word on Paths
Security
UNIX and security
Multiple user implementation
Root
Old Stuff in New Terms
INITs in Mac OS X
Fonts
FKEYs
Printing from Mac OS X
Disk First Aid and Drive Setup
Startup Items
Mac OS 9 Control Panels and Functionality mapped to Mac OS X
New Stuff to Check Out
Review Questions
Review Answers
Further Reading
Change history:
3/19/01: Removed comment about UFS volumes not being selectable by Startup Disk.
3/23/01: Minor grammatical edits.

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Operating Systems 101
Apart from the many architectural and design changes “under the hood” in Mac OS X,
the two major functional benefits are pre-emptive multitasking and protected memory.
This section will explain what these terms mean, contrasting them with Mac OS 9.
Contents of this Section:
Mac OS 9 and Cooperative Multitasking
Mac OS X: Pre-emptive Multitasking and Protected Memory.
Mac OS X: Symmetric Multiprocessing

Learning Objectives:
At the end of this section, you should be conversant with the concepts of:• context switching• cooperative multitasking• pre-emptive multitasking• protected memory• symmetric multiprocessing

Mac OS 9 and Cooperative Multitasking
Mac OS 9 is the latest generation of an operating system architecture that has been
evolving since 1982.
When the Macintosh was first released, the operating system was designed to support asingle user using a single program on a single computer.
A typical computer program is a sequence of instructions stored in memory. Most
instructions operate on data stored in either the microprocessor (registers) or in RAM.
Instructions typically are designed to move information from one place to another, toperform logical comparisons, and to jump to subroutines based on the results of suchcomparisons.
As the microprocessor executes these instructions, it maintains track of where it is via a
special register called a “program counter.”At the most basic level, when such a program is being run, it has total control over thecomputer. Only the code the program counter is pointing to gets executed.
In 1984, a typical program would be comprised of a “main event loop.” This was assequence of code that would run hundreds of times a second. A command
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(GetNextEvent) would communicate with the rest of the operating system. This wouldstop the current program from executing, passing control to the operating system. The
operating system would kindly save the microprocessor state (including the program
counter) and restore its own state. It would then start performing a number ofmaintenance activities. When it was finished, it would tell the application what happenedin the meantime: what keyboard, mouse, and device activity had occurred. The
application would then react to this information appropriately, executing menu
commands, opening dialogs, etc.
Application

Processor

In the late 1980s, when the Mac started to acquire more and more RAM, a wonderfulprogram came out, called Switcher. This allowed more than one user application to beresident and active in memory at one time. So one could be running MacWrite at one
time, then switch over to MacPaint, edit a picture, copy it, switch back to MacWrite, andpaste it in. This approach was called context switching. The applications weren’trunning simultaneously—only one would be running at once. What Switcher did wassave the state of one application, restore the state of another, and switch the context theuser was dealing with.
Inactive Application

Active Application
User chooses app
to use.

Processor

In the early 1980s, this concept was updated into an extended service called MultiFinder.
This did more or less the same thing as Switcher. As MultiFinder evolved, more
underlying OS support was provided, until a paradigm that supported cooperative
multitasking was introduced.

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Inactive Application

Active Application

Processor

Active application calls
WaitNextEvent, OS
passes control to nextapp.

In cooperative multitasking, the operating system was modified such that each time
GetNextEvent was called, instead of just updating its internal business, the operating
system would also allow other applications (or processes) in the system to update at thesame time.

The key for successful implementation of this approach was that all running processes
had to allow (cooperate with) the OS to perform this function. If a program stopped
calling GetNextEvent, then the microprocessor would continue running that program’s
codes until the program either called GetNextEvent again, or quit. There was no way forthe operating system to interrupt it. When this state of affairs existed, the only control theuser would have would be to move the mouse around. User activity such as mouse clicks
wouldn’t work, since the application was behaving poorly.
GetNextEvent was later modified and replaced with a series of successors, which allowed
programs to specify a self-assessment of their importance to the OS. For example, agame would want absolute top priority, but a background spreadsheet calculation mightjudge itself to be less important and request a lower priority.
This is pretty much the state of affairs in Mac OS 9.

Mac OS X: Pre-emptive Multitasking and Protected Memory.
Mac OS X does away with all this. It introduces a concept called a “scheduler,” which isa layer of interaction between the applications and the microprocessor. Now, anapplication can be written that may have no interface components at all—say, a purenumerical simulation that an astronomer might write, which could be very timeconsuming—and leave the user with total control of the operating system and allfunctionality.

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The scheduler is part of a component of the OS called the “kernel,” which loads before
all other applications and manages the most elementary behavior of the operating system,
such as process, memory, and device management. When you launch an application, thescheduler is put in control, allocating a certain percentage of CPU time to that process.
When the scheduler decides that the process’s time is up, it will take control back andallows the next application to start introducing code. Thus, the scheduler can pre-empt
any running process if it wishes to do so.

Inactive Application

Inactive Application

Active Application
Scheduler decides towake up inactive app.

Scheduler

Scheduler decides
app's time is up,
passes control tonext app.

Processor

This introduces a level of indirection between the application and microprocessor. This
indirection also allows some other good things to go on. Architecturally, for thescheduler to work, memory activity must be tightly controlled. So as an application’scode is executed, checks are made to ensure the application’s memory activity stays
within bounds. If such an application tries to write data in another application’s space, orinterfere with the operation of critical system resources, it won’t be successful. This isprotected memory.
The combination of these two features lends itself to an operating system in which single
rogue applications or processes can’t take the entire system hostage. If there’s a bug inan application, the application will simply crash, resulting in its memory immediately
being released by the system. Everything else will run fine. Applications no longer haveto respect the interests of other applications, so interaction issues can’t arise. They can beas badly behaved as their developers want, but the core operating system will remain
stable and the user will remain in control.

Mac OS X: Symmetric Multiprocessing

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6Pre-emptive multitasking and protected memory are facilitated by the UNIX foundationof Mac OS X. The behavior of schedulers and kernels in UNIX have been intensely
studied over the last 20 years. UNIX is the operating system of choice in most university
computer science programs, and is very well understood.
The design of UNIX kernels has kept pace with the evolution of hardware technology,
including support for multiple processors. Mac OS X provides support for two
microprocessors via a technology referred to as symmetric multiprocessing (SMP).
This is a complex scheme in which the operating system strives to keep both
microprocessors (when available) busy in an efficient manner, thus multiplying system
and application performance.
Unlike previous versions of the Mac OS, developers do not need to specifically code formultiple processor support, so any application will conceivably run much faster with two
processors available. Applications which support multithreading will run even faster.
This reveals yet another fallacy in the traditional “megahertz wars” between
microprocessor and computer vendors: a single metric such as clock speed fails torepresent actual performance improvements produced by unique architectural
innovations. Increasingly, such measurements fail to represent actual system
performance, even within processor families.

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Components of Mac OS X
Mac OS X encompasses many different technologies. This section outlines the major
ones: Darwin, Quartz, OpenGL, QuickTime , Application Services, the Application
Environments, and Aqua.

Contents of this Section:
The layered approach
DarwinCore Services
Graphics Services
Application Environments
Aqua

Learning Objectives:
At the end of this section, you should be conversant with the concepts of:
DarwinMach
BSD
Core Services
Open Source
QuickTime
OpenGL
QuartzApplication Environments
CarbonJava
Cocoa
Classic

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The Layered Approach
One way of looking at operating system design is the “layered” approach.

In this approach, the services on each successively higher layer are directly dependent onservices provided by the layer beneath them. Thus, Darwin is the bottom (core) layer,
encompassing the kernel, the heart of the operating system. Core Services sits on top of
that, and so on. An important distinction is that most higher-level services can’t (orshouldn’t) make a call that penetrates the layer underneath them. For instance, anapplication sitting at the top layer generally won’t penetrate down to Darwin. Such an
application would call services in the module underneath it, that one would repeat theprocess, and so on. The major exception is Classic, which, due to the needs of supporting
the Mac OS 9 environment, interacts directly with every level of the OS.
This approach allows for the creation of very complex operating environments which arenonetheless very robust. As long as each layer is thoroughly tested, then each successive
layer does not need to worry about the behavior and design of services underneath it.
This allows for the creation of abstract, transportable application environments at the
topmost levels, and spares the typical software developer from having to have a deep
understanding of the underlying operating system. This, in turn, will tend to accelerateapplication development and application quality.
Tip: You can probably exclude a problem with a lower-level layer(thus obviating the need for reinstallation of system software) if aproblem is restricted to a single application using a type of service.
In general, if a lower layer breaks, there will be a cascading effectto everything that sits on top of it.

DarwinDarwin is the heart of Mac OS X. It is comprised of two major technologies: Mach and
BSD.

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Mach is a UNIX technology developed at Carnegie-Mellon University in the late 1980s
and 1990s. It’s a robust, “open source” operating system, which is used to provide
memory and task implementation services. Darwin uses Mach 3.0. Mach provides
memory management, memory protection, process scheduling and interprocess
communication services.
BSD is the Berkeley Standard Distribution. Back in the early 1980s, the University ofCalifornia at Berkeley was a major center of focus of UNIX activity. They adapted
AT&T’s System III and provided more sophisticated process management and network
functionality. They distributed their version of UNIX, called the Berkeley Standard
Distribution, for what amounted to the cost of goods. This, in turn, was widely adaptedby academia and turned into the source material for further innovations by companies
such as Sun Microsystems. Darwin incorporates elements of the BSD 4.4 distribution,
which provide file system support, network services, symmetric multiprocessing support,
and multi-threading facilities.
BSD also provides support for the “shell” environment. Simply put, a shell is aninteractive, command-line interface that allows the user to control the operating system
and accomplish tasks. UNIX is often confused with its shell interface. However, the best
way to view the shell is as one of many possible ways to manipulate the core services.
For three decades, the easiest way to do this was via command-line interfaces, such as theBourne shell (sh), the C-shell (csh), the Korne shell (ksh), tcsh, bash, and many others.
However, starting in the 1980s, manufacturers started to experiment with many different
ways to provide similar control via graphical interfaces, such as SunView, Motif, XWindows, and others. None of these graphical approaches has reached the level ofintegration that Mac OS X provides.
The shell environment is completely optional for most users. It provides maximum
control over the operating system. It will appeal mainly to advanced systemadministrators, computer science students and experienced UNIX users. The only way to
get to the shell in Mac OS X is for the user to locate the Terminal application and open it(/Applications/Utilities).
Darwin is an Open Source environment. Beyond the scope of this training, suffice it to
say that Open Source allows developers outside of Apple to modify fundamental
components of the system software at the source code level. It is expected that this will
drive innovations in the evolution of Mac OS X. More information can be found at
http://www.apple.com/opensource.

Core Services
The Core services layer provides a number of higher-level utilities of interest to
applications, including a number of services analogous to the Operating System Utilities
from Mac OS 9. Carbon interfaces (see below) are provided for these utilities, which
include services such as the Resource Manager, Time Manager, Alias Manager, Apple
Event support, etc.
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Core Services is associated with the CoreServices framework (CoreServices.framework).
A framework is analogous to a shared library. More on that later.
Core Utilities is another framework of Core Services. This provides a number of services
that help facilitate inter-application communication as well as other services.
Open Transport also sits in the Core Services layer.

Graphics Services
Mac OS X supports a rich variety of graphics services.
Quartz is the modern heart of the user experience, superseding QuickDraw and related
managers, and directly supporting the Aqua user experience (see below). The emphasison Quartz is supporting crisp two-dimensional graphics to support the user interface,
including on-the-fly rendering and anti-aliasing. Quartz is based on the Adobe Portable
Document Format (PDF). PDF is the standard for electronic document distribution
worldwide. PDF is a universal file format that preserves all of the fonts, formatting,colors and graphics of any source document — regardless of the application and platform
used to create it.
OpenGL is a sophisticated open-source rendering system. Developed as an open source
project (OPEN Graphics Library) by Silicon Graphics in the 1990s, OpenGL supports
advanced 3D rendering. It is of primary interest to game and multimedia developers. It
also has a role in scientific visualization. OpenGL replaces QuickDraw 3D, which is nolonger supported.
The third element of graphics suppport, QuickTime, is the same old QuickTime 5 weknow and love, with no change in functionality.

Application Environments
One of the key challenges in developing Mac OS X was the need to support older
application packages while simultaneously providing a modern platform that new
applications could support.
The Classic environment supports launching Mac OS 9.1 as a process. Once this process
opens, applications can be run. It is important to understand that Classic provides theenvironment to launch Mac OS 9.1—it isn’t directly simulating 9.1. It utilizes acomplete, intact, bootable Mac OS 9.1 System Folder located on one of the partitions.
The Classic environment supports older, non-updated applications, including 68K
applications. Since launching the Classic environment also involves “booting” Mac OS
9.1, user extensions are also available to applications running within the Classic
environment.
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The Carbon environment is a set of Application Programmer Interfaces consistent withMac OS X’s design objectives. Carbon includes versions of about 70% of the APIs
present in Mac OS 9.1. Carbon applications can run in Mac OS 9.1 (with CarbonLibpresent) or in Mac OS X. They will automatically take advantage of all the interface
features of Aqua. When you launch a Carbon application, it’s indistinguishable from anyother Aqua application.
The Cocoa environment is an object-oriented framework that provides development tools(Interface Builder and Project Builder, which can also build Carbon and Java apps) andservices that allow such applications to interact with one another and take advantage of avariety of advanced libraries. Cocoa applications look the same as Carbon applications to
end users.
The Java environment supports 100% Java 2 applications and applets. Java may be
selected as a development language by the Cocoa developer tools. One of the advantagesof Java development is that applications developed in Java are code-compatible withother computers running the same version of the Java Virtual Machine.

Aqua
Aqua is where it all comes together, a new look and feel for the Macintosh user
experience. It makes extensive use of animation and rendering to provide a stimulating
and pleasing work environment.

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The most significant new interface features of Aqua include:• The look & feel.
• The Dock, which is a user-customizable toolbar-like repository for applications
and documents. In this respect, it replaces the Launcher from Mac OS 9 as wellas the traditional uses for the Apple menu.
• The extensive and natural support for multiple users.
Control panels are now known as System Preferences, and can be accessed via the Dockor via the Utilities folder.
Training for Aqua is beyond the scope of this document. Please refer to the actual
software or to http://www.apple.com/macosx.

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Useful Mac OS X Jargon
Contents of this Section:
Bundles
Frameworks
Umbrella Frameworks

Learning Objectives:
At the end of this section, you should be conversant with the concepts of:
Bundles
Frameworks
Umbrella Frameworks

Bundles
Bundles are a new way of packaging applications. In Mac OS 9, an application often
resided in several directories, such as shared libraries in the Extensions folder, and theexecutable application in some arbitrary folder. In addition, an application itself wascomprised of two “forks” within a single file: a data fork (which in the case of PowerPC
code contained the program’s executable code), and a resource fork. The resource fork
contained templates for various elements of the user experience, such as the names ofmenus, menu items, dialogs, window types, the icon the Finder should display, etc.
In Mac OS X, this has changed. A bundle is a collection of these various data elements(executable code, resource information), each of which is a single file. These files aregathered together in a directory and then presented to the user as a single, doubleclickable file. In Mac OS X, applications are bundles.
Tip: Icons have an .icns suffix. You can edit them with Icon
Composer or Pixie, two utilities which are distributed on theDeveloper CD in /Developer/Applications.
Tip: A bundle may be opened, such that you can see the individualcomponents of the directory, by option-clicking on its icon.
Tip: Bundles are sometimes called “packages.”

Frameworks

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A framework is a dynamic (loaded only when used) shared library along with its
associated resource information. This information is packaged as a bundle. This isanalogous to the shared libraries which are placed in the Extensions folder in Mac OS 9.
Shared libraries contain code that can be shared by multiple applications. For instance, if
a manufacturer produces a suite of productivity software, odds are there’s going to be agreat deal of similarity within their code. Therefore, from a development anddeployment perspective, it makes sense to allow the applications to share common code.

Umbrella Frameworks
Umbrella frameworks are generally system software-level functions. This conceptrefers to a framework which itself contains two or more subframeworks. Generally thisshouldn’t come up in support.

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Mac OS X Installation
Mac OS X is easy to install, taking a comparable amount of time as Mac OS 9.1. There
are a number of concepts which must be understood with respect to installation options
as well as to the organization of data on the hard drive.
Contents of this Section:
Initialization Options
Installation Options
Startup Keys
Mac OS X Setup Assistant
Mac OS 9 and Classic
Standard Directory Names
Quick Answers: Where do my __________ go?
More Directory Names
A Word on Paths

Learning Objectives:
At the end of this section, you should be able to:• Explain the differences between UFS and HFS.
• Identify the three package types that can be installed.
• Identify the three new startup key sequences.
• Explain to users why Setup Assistant is a Good Thing.
• Explain what it takes to run Mac OS 9.1 in Classic.
• Explain the limitations of Classic mode.
• Explain the use behind the standard directory names.
• Differentiate between system-level and user-level directories.
• Be able to locate the Mac OS X equivalents of Mac OS 9 directories.
• Be able to explain why there are invisible folders and files in Aqua.
• Be able to read a path name and understand what it refers to.

Initialization Options
A hard drive may be partitioned into several volumes by using Drive Setup, which is now
a component of Disk Utility. One of the reasons for doing this is for robustness (e.g., adeveloper who might want to limit directory damage caused by debugging buggy
software), organization, or performance (e.g., users doing video editing may frequently
wish to “de-fragment” their drives by erasing them). Partitioning is a solution which is
supported by Apple.
On installation of Mac OS X, the user has the option of selecting two file formats: UFS(Unix File System) and Mac OS X Extended (HFS+). Most users will want to use Mac
OS X Extended. A partition formatted with UFS will not mount in a Mac OS 9 startup
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environment. Nor will it be available as a shared disk via Network File System (a way of
sharing data in a workgroup environment).
Note: Mac OS X must be installed on either a Mac OS X Extended or a
UFS volume. The core system cannot be installed on Mac OS X Standard(HFS) volumes, though it can read data on such volumes.
Tip: It is not necessary to erase a volume if it’s already formatted as Mac
OS X Extended.
Tip: Installing Mac OS X over it will not delete any data.
Caution: Mac OS X has to go on a partition that is within the first 8 GB of
the device.

Installation Options
Users have three installation options:
The Base System and Essential System Software packages will always be installed.
The user may opt not to install the BSD subsystem. This is not recommended, as it may
break certain types of network services. In particular, parts of the Network Utility, FTP,
NFS, and Telnet services will break.
Tip: If a user reports problems using these services, make sure that BSD
wasn’t turned off in an attempt to save disk space.
The user may opt not to install the many print drivers.

Startup Keys
At system start time, there are three startup key sequences which will be handy:
Holding down the option key will produce a volume list, allowing the user to selectwhich system to start from. This is a hardware-based feature, and may not be available
on all systems.
Holding down the command and v keys will put the system into “verbose” mode, suchthat you can watch the status of the system as all of the drivers and packages load.

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17Holding down the command and s keys will put the system into “single-user” mode, andput you right into a shell. This should only be used in extreme troubleshooting situations
and only if you’re comfortable with shell-level system administration.

Mac OS X Setup Assistant
After installation, the user will be required to go through the Mac OS X Setup Assistant.
This will register the user with Apple, as well as configure the initial Internet preferences,an iTools account, and mail services.
Important: Many users will have a natural tendency to open Classic (seebelow) in order to configure their preferences, simply because they areaccustomed to this environment. Several control panels will not be
available, due to potential conflict with Mac OS X’s functionality. Others
may appear to have confusing configuration options. In particular, network
services will be overridden by Mac OS X. For example, Mac OS X’s
Network System Preferences might be set up to use DHCP to gain its IP
address, but Classic will show a static address manually assigned. When
troubleshooting issues such as connectivity, it’s important to ask the userwhether any attempt was made to modify system-level settings fromClassic. All of this is a good reason to extoll the virtues of properly
completing the Setup Assistant with your customers—particularly old-time
Mac users who are accustomed to setting up their environments“manually,” via direct manipulation of control panels.

Mac OS 9 and Classic
Classic is an environment which supports the launching of Mac OS 9.1 as a process. In
order to support this feature, Mac OS 9.1 must be installed on the hard drive. The Mac
OS X installer does not install Mac OS 9.1. Mac OS 9.1 is, however, bundled as aseparate installation CD in the retail distribution.
Tip: Mac OS 9.1 can be installed on the same volume as Mac OS X, or on
another volume. You can also install Mac OS 9.1 on the same volume as
Mac OS X before or after Mac OS X is installed.
The process of opening the Classic environment is initiated by either using the Classic
System Preference, or by opening a Classic application.
Applications running under Classic do not enjoy the benefits of memory protection
within the Classic environment. So they can still damage the running Classic
environment or other applications if they fail. They cannot damage processes outside of
the Classic environment.

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Since Classic itself is a process in Mac OS X, Classic applications do enjoy the benefitsof pre-emptive multitasking, i.e., if they do hang or crash, the user can still control thesystem and other non-Classic applications. However, in this case other currently-runningClassic applications will prove to be problematic. When this happens, the user can forcequit out of Classic by using the Classic System Preferences.
Keep in mind that since Classic is a hosted environment, some functions may not be
available. So if control panels fail to open or options are dimmed, that’s why.
If the user should discover that there’s an important function that can only be
accomplished by launching Mac OS 9.1 (as opposed to Classic), the Startup Disk System
Preference can be used to select the Mac OS 9.1 System Folder. If the user then restarts,
the system will use Mac OS 9.1. The user can return to Mac OS X by using the Startup
Disk Control Panel.

Standard Directory Names
In Mac OS 9, standard directories included Apple Extras, Applications, and the System
Folder. Mac OS 9.1 introduced minor variations, such as “Applications (Mac OS 9).
The organization of Mac OS X is quite a bit different.
There are five important directory names the user will encounter:
Applications, the folder which contains application software the user can use to be
productive. The Applications directory will typically contain a Utilities directory, whichcontains applications that can be used to monitor or administer system behavior.
System, which contains critical Mac OS X system software. Typically the user will not
add or remove items from anything in this folder: it’s designed to remain pristine.
Library, where preference information is located. In the UNIX world, though, Libraries
tend to contain much more than the sort of information contained in typical Mac OS 9preferences files. In many cases, Library files contain extensive instructions on how
applications should behave. In Mac OS X’s case, Libraries are where fonts, desktop
pictures, modem scripts, printer drivers and many types of plug-ins also reside.
Users, where user information resides.
Documents, where user documents automatically stored.
Now it gets a bit weird.
This scheme is replicated throughout the system. So at the top level of the hard drive,
you’ll see folders (Applications, System, Library and Users) which are available to allusers on the system.

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System and Users are owned by the system, and you’ll need “root” access (covered later)
to manage them. Typically a user will not want to muck with them directly. Things thatneed to be adjusted (such as creating or deleting users) can be adjusted using theappropriate utilities.
But take a look inside System: you’ll see a Library file. This is consistent with thenaming philosophy described above—these are preferences, plug-ins, etc., that the systemneeds to support itself.
Back to the top level: Applications and Library contain data of appeal and interest to allusers of the system. Any Administrator-level user or above can delete or add material tothese folders.
Continuing this walk-through, go into the Users folder. Note that the active logged inuser has the house icon. Go into one of the User folders.
You’ll find the same structure as at the top level of the hard disk, minus the Systemfolder. This is to support the notion that users may have their own private data they needto have installed. Typically, when a user installs application software, it will be locatedin the user’s private Applications folder, Library, etc., unless a conscious decision ismade to share it with all other users.
Tip: It’s a good idea to evangelize this type of thinking with users. Many
people are accustomed to thinking in terms of single-user/single-system,
but as their skill levels evolve, they may wish to share their computer withother people on the network, set up FTP access, etc. Users aren’t losing
anything by taking this approach. Say, for instance, that a font’s installed
in a personal Library directory—that font will still be available toapplications installed in the top-level Applications folder.
Tip: Note that items on the desktop are maintained in the Desktop folder
in the user’s home directory.
Note: The default folders within a user’s directory are, by default, private,
and accessible only to that user. The main exception being the “Public”
and “Sites” folders.

Quick Answers: Where do my _______ go?
In the following, myhome refers to a user’s home directory. E.g., if a user’s login name is“Mike”, /Users/myhome/Library would be /Users/Mike/Library.

Item

Mac OS 9

Mac OS X

Fonts

System Folder: Fonts/Users/myhome/Library/Fonts/Library/Fonts

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Apps
Documents

Applications
Documents

Desktop Pictures
Control Panels

Anywhere
System Folder:
Control Panels
System Folder:
Extensions
System Folder:
ColorSync Profiles

Extensions
ColorSync Profiles
GeneralPreferences
Keychains

Modem Scripts

SoundsStartup Items
Printer drivers

System Folder:Preferences
System Folder:Preferences:
Keychains
System Folder:
Extensions: Modem
Scripts
System Folder:
SystemSystem Folder: Startup
Items
System Folder:
Extensions/Users/myhome/Applications/Users/myhome/Documents/Library/Documents/Library/Desktop Pictures

N/A
N/A/Library/ColorSync/Profiles/Users/myhome/Library/ColorSync/Pr
ofiles (user-created)/Library/Preferences/Users/myhome/Library/Preferences/Users/myhome/Library/Keychains/Library/Modem Scripts/Library/Audio/Sounds/Users/myhome/Audio/Sounds?
/Library/Printers/Users/myhome/Library/Printers

More Directory Names
But all this is just the tip of the iceberg. Since there’s a UNIX environment runningunder the hood, there are actually quite a few more directories to support standard shellbased tools. These directories are all invisible to users operating in the Aqua
environment.
If you open up the Terminal application (go to the root-level Applications folder, then to
Utilities), you’ll find that you can access Darwin’s command-line interpreter. The default
environment is called “tcsh,” a popular variation of the C-Shell. Using the ls /command, you’ll see these invisible folders and files. These files are there to support a
standard shell environment as well as critical system resources.
Discussion of these is beyond the scope of this document, but any good UNIX reference
book should be more than sufficient to explain this organization. Suffice it to say that for
typical support purposes, a Mac OS X support provider won’t have to deal with this levelof the operating system. We mainly raise it here since many utilities will reveal thepresence of these files.

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CAUTION: These invisible files are supposed to be there. Don’t deletethem to save disk space. Bad things could happen.

A Word on Paths
The directory is structured as a “tree.” The normal way of referring to paths is to start at
the top level (/) and then separate folders, working down, by slash (/) signs.
So / is the root directory, the top of the hard drive.
/Applications refers to the Applications folder.
/Applications/Utilities refers to the Utilities folder, which is located inside theApplications folder.
/Applications/Utilities/Terminal refers to the Terminal application in the Utilities

folder.
Note that almost every file and application on the system actually has asuffix indicating what it is. E.g., “terminal.app” to describe the Terminal
application. This suffix is hidden from the user, but you will be able tosee it in a terminal environment. So you may also see paths written in theform of /Applications/Utilities/Terminal.app. Don’t let this throwyou.

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Security
UNIX is a fairly secure operating system, but it’s only as secure as how well it’s
maintained. This section discusses some of the philosophical issues behind UNIX systemsecurity and security in general.
Contents of this Section:
UNIX and Security
Multiple User Implementation
Root

Learning Objectives:
At the end of this section, you should be able to:• Discuss UNIX security in general.
• Discuss the three types of file permissions.
• Discuss the three ways file access can occur.
• Enable or disable root access.

UNIX and Security
UNIX was originally developed to be an insecure system. Original builds in the 1970s
had no login process, and the rudimentary networking capabilities at the time were basedon the “good neighbor” principle. That mode of thinking quickly ran into the real world,so the following ten years saw the introduction of increasing layers of security, including
encrypted passwords, login dialogs, file system security, and so forth.
Once UNIX broke out of the academic world, its main susceptibility to attack came inthree flavors:
1. “Cultural” attacks. I.e., if someone trying to access a system knew something about
the user base, intelligent guesses could be made as to passwords. Such attacks could
come from insiders (the user lists traditionally stored in /etc/passwd were often
world-readable, i.e., everyone on the system could read them) or from external
people. This is still a concern with any “closed” system.
2. Misinstalled software. Some software packages were installed improperly (e.g., in
one case if a word processor was installed incorrectly by a “root” user, a non-root
user could drop into a shell-command mode and execute commands as root). Othersoftware packages were distributed with “debugging” modes turned on, whichallowed attackers access to the system. This led to a fad of “worm” attacks, startingwith the Morris worm. The UNIX community grew up quickly at this point, andmost implementations are now fairly secure. Virus attacks have not generally been
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associated with the UNIX world, but note that application environments such as
Classic are still vulnerable.
3. Denial of service attacks. These can range from flooding a system with network
requests to a user grinding the processor to a halt through creative shell scripts.
Depending on the environment, these can still be issues.
Culturally, UNIX systems tended to be locked away in secure machine rooms, so thethinking on security had it that any attack had to come in through a network or terminal.
However, with the advent of inexpensive UNIX implementations that could run on
personal computers, physical security has become an issue. In the case of Mac OS X, forinstance, if a user boots up with a Mac OS 9.1 system CD, he’ll have access to data in thesystem. Some manufacturers have striven to produce “secure UNIX” environments withencrypted file systems and the like.
Bottom line: the only truly secure computer is one that is locked in a secure room and notconnected to a computer network. We raise these points here mainly to discourage
enthusiasts from overstating the robustness of the security environment. There are limits
to the security of any operating system, but this is not to say that Mac OS X is limited
compared to other UNIX implementations or NT.

Multiple User Implementation
Mac OS X supports multiple users. As described above, each user has his own work
environment, his own applications. UNIX-style access security applies.
Tip: When a user chooses to restart Mac OS X after logging in, a login
prompt will not be provided by default. This behavior can be changed in
the Login System Preferences.
While an in-depth discussion of such security is beyond the scope of this training, we’ll
highlight the major concepts.
Any file has three types of access permissions: read, write, and execute. These can beintermingled.
If a write bit is set, then users can modify a file or create a file in a directory.
If the read bit is set, then users can read a file or list a directory.
If the execute bit is set, then the file can be opened as an application and the operating
system will try to run it.
There are three permissions groupings:
User, which applies to the owner of the file.
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Group, which applies to the group the file belongs to. A file may only belong to one
group.
Other, which applies to anyone on the system.
These can be intermixed. For instance, by default you can do whatever you want withyour file (read and write bits set; execute set if the file is an application).
Groups are collection of users with a common attribute. A file can belong to a group.
This assignment is accomplished (via UNIX) by the chgrp command, and in Aqua via theUsers System Preference dialog. The permissions (read, write, execute) you assign tothis attribute applies to members of the assigned group.
The “Other” category is a universal setting, setting privileges for all users on the system.
The permissions apply to anyone on the system.
In terms of hierarchy:
The OWNER of the file can set any file permissions.
Once permissions are set, the owner can use the file.
Owner permissions override all other permissions.
Group permissions override the “Other” permissions.
Any good UNIX reference covers these concepts in detail. We recommend that support
providers learn a bit more about the UNIX implementation of permissions; it will help
you to understand what the user interface is doing “under the hood.”

Root
Root is the ultimate superuser. Remember, the first user is made “administrator” bydefault. This gives them access to everything on the system except for the System folder.
The next step up is to give them access to the System folder. This can be very dangerous,
inasmuch as files deleted or modified can affect the system at the most fundamental level.
In general, root access should only be used by people very comfortable with UNIX at thesystem administration level.
You can enable root by using the NetInfo Manager and using the options in the Security
hierarchical menu under the Domain menu.

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Old Stuff in New Terms
Almost everthing that was present in Mac OS 9 has been carried over to Mac OS X. The
items and concepts left behind are either obsolete or have been integrated into the newuser experience.
Contents of this Section:
INITs in Mac OS X
Fonts
FKEYs
Printing from Mac OS X
Disk First Aid and Drive Setup
Startup Items
Mac OS 9 Control Panels and Functionality Mapped to Mac OS X
New Stuff to Check Out

Learning Objectives:
At the end of this section, you should be able to:•
Explain why leaving extensions and control panels with INIT code behind
was a good idea.
•
Identify the four types of supported fonts.
•
Recognize that FKEYs are no longer supported.
•
Identify changes in the print architecture, especially that Print Center isat the heart of the new user experience•
Understand that desktop printers no longer exist.
•
Understand the functionality of Disk Utility.
•
Understand how to set Startup Items.
•
Describe how functionality has been deployed in the new interface.
•
Leave with a shopping list of items to explore on your own.

INITs in Mac OS X
INITs were a way of having code load and execute at boot time in Systems 4-7 and Mac
OS 8-9. They got their name from the fact that they were saved as short code segments
in an INIT resource within a file.
A couple of years after the original Macintosh computer was released, third-party
developers realized they could patch system-level commands. The original Macintosh
shipped with a huge library of services that third-party developers could use. These werereferenced via an Application Programmer Interface (API), and were referred to by name.
When a developer wished to use one of these commands, he’d simply insert it in the codeof the program. When the program was being executed, the microprocessor would stop
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dispatch table.” Based on the formatting of the command, the microprocessor would go
to an area within the table and resume execution at an address pointed to by that sectionof memory.
So some developers figured, why not save the address in the trap dispatch table and put
an address to THEIR code instead. Then, when their code finished executing, the thirdparty code would call the original address in the trap dispatch table.
By choosing the right command (e.g., GetNextEvent, discussed above), a developer could
thus ensure that his code was called several times a second. This led to the advent of ahuge number of utilities that patched the system, ranging from screen savers to menubar
utilities.
The problem, though, is that they WERE patching fundamental aspects of the system—insome cases, there would be dozens of third-party processes hanging off popular traps, andin at least a few cases, a single third-party package might patch dozens of systemcommands. So a situation arose where INITs of increasing complexity (and appeal tousers) were being developed. The problem was that if any of them failed, due to coding
errors, the exploitation of undocumented aspects of the operating systems, etc—thewhole machine could crash.
This led to the backbone of Mac stability troubleshooting: get the machine back to known
configuration (factory default), re-introduce extensions slowly, test for stability, and try
to identify what might be causing the problem.
The term “INIT” fell by the wayside in the late 1980s, to be replaced by Control Panels
and Extensions. Control Panels and Extensions might or might not have INIT code inthem.
While Mac OS X does not support this concept per se, it is an Open Systems architecture,so third-party developers may well figure out a way to patch the kernel. In addition, thekernel itself supports “kernel extensions,” but these are designed to support the very
lowest levels of the system. They aren’t designed to support higher-level processes thatwould provide access to Core Services or the graphics services.

Fonts
Mac OS X supports TrueType, Type 1, UniCode, and legacy bitmap fonts.
Tip: Mac OS X will not automatically copy fonts from a pre-existing Mac
OS 9 System Folder and make them available to users in Aqua. The user
will need to manually copy fonts from the Fonts folder inside the Mac OS
9 System Folder and put them in /Users/myhome/Library/Fonts.
Tip: Applications running in Classic will only have access to the Fonts
installed in the Classic Mac OS 9 System Folder.
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FKEYsIn Mac OS 9, FKEYs were supported that allowed the user to do a screen capture at any
point via command-shift-3. This function is no longer available in Mac OS X. Instead,users should use the Grab application, which is located in /Applications/Utilities.
Once a screen image capture is performed, the document will be opened in the Preview
application, from whence the image can be saved and/or printed.

Printing from Mac OS X
Mac OS X has an all-new print architecture. The heart of the user’s printing experienceis the Print Center. This allows the user to select the current printer and to monitor andmanage the progress of print jobs.
PDF is the new standard document format. Applications can save documents to a deviceindependent PDF format when appropriate.
The device driver architecture also supports a much easier driver development scheme,
utilizing a framework called the I/O Kit. This will result in new print drivers being
available more quickly for Macintosh users, as well as a more robust printing
environment. Drivers for a large number of common printers are pre-installed with Mac
OS X (see /library/printers).
Mac OS X does not support desktop printers.

Disk First Aid and Drive Setup
Disk First Aid and Drive Setup have been replaced by Disk Utility(/Applications/Utilities/), which provides a clean new interface offering all thefunctionality of its predecessors.

Startup Items
In Mac OS 9, users could select items to start up as the Finder loaded by putting aliases
or files into the Startup Items folder.
In Mac OS X, the user may select items to open automatically at startup by going to the
Login System Preferences dialog.
Startup Items are located at/Users/myhome/Library/Preferences/loginwindow.plist
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This is not a user-editable list. Use the Login System Preferences dialog instead.

Mac OS 9 Control Panels and Functionality mapped to Mac OS X
This section correlates features provided by Mac OS 9 to the equivalent functionality in
Mac OS X.Note that in Mac OS X, a number of items (such as the need for the Memory
control panel) have been rendered obsolete, while the functionality of other items (suchas the Launcher) are integrated into the new user interface.

Function
Desktop pictures
ThemesAppearance
Font Preferences
Desktop Patterns
Sound Effects
Collapsible Windows
Scroll Arrow Placement
Network services
Apple Menu
configuration
ColorSync

Mac OS 9
Appearance control panel
Appearance control panel
Appearance control panel
Appearance control panel
Appearance control panel
Appearance control panel
Appearance control panel
Appearance control panel
AppleTalk control panel,
TCP/IP control panel
Apple Menu Options control
panel
ColorSync control panel

Control Strip
Date & Time

Control Strip control panel
Date & Time control panel

Energy Saver

Energy Saver control panel

Extensions Manager

Extensions Manager control
panelFile Exchange control panel
File Sharing control panel
File Synchronization control
panel
General Controls control
panelFile Exchange
File Sharing
File Synchronization
General Controls(Launcher, Menu
Blinking, Insertion Point
Blinking, Document
folder preferences,“check disk” function.
Infrared
Global Internet
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Infrared control panel
Internet control panel

Mac OS X
Finder: Finder Preferences
N/A
General System Preferences
N/A
N/A
N/A
N/A
N/A
Network System Preferences
N/A
ColorSync System
Preferences
replaced by Dock
Date & Time System
Preferences
Energy Saver System
Preferences
N/A
N/A
Sharing System Preferences
N/A
N/A

N/A
Internet System Preferences

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application preferences
Keyboard settings
Keychain access
Launcher
Location Manager
Memory control
Modem
Monitor control
Mouse control
Multiple Users
Numbers
QuickTime settings

Keyboard control panel
Keychain Access control
panel
Launcher control panel
Location Manager control
panel
Memory control panel
Modem control panel
Monitors control panel
Mouse control panel
Multiple Users control panel
Numbers control panel
QuickTime settings control
panel
Remote Access control panel

Remote Access

Keyboard System Preferences/Applications/Utilities/
Keychain Accessreplaced by Dock
Network System Preferences,
Apple menu
N/A
Network System Preferences
Displays System Preferences
Mouse System Preferences
Users System Preferences
International System
Preferences
QuickTime System
Preferences
Network System Preferences,/Applications/Internet
Connect

Software Updates
Sound control
Speech control
Startup Disk control

Software Update control
panel
Sound control panel
Speech control panel
Startup Disk control panel

TCP/IP control
Text behavior

TCP/IP control panel
Text control panel

Trackpad control
Web sharing
Chooser AppleTalkselection
Printer selection
Connect to IP server
Select AppleShareserver
Key Caps
Calculator
Favorites
Network Browser
Scrapbook
Note Pad
Stickies
Erase Disk
Finder display options

Trackpad control panel
Web Sharing control panel
Chooser

Software Update System
Preferences
Sound System Preferences
Speech System Preferences
Startup Disk System
Preferences
Network System Preferences
International System
Preferences
Mouse System Preferences
Sharing System Preferences
Network System Preferences

Chooser
Chooser
Chooser

Print Center
Finder, Go menu.
Finder, Go menu.

Apple menuApple menuApple menuApple menuApple menuApple menuApple menu
Special menu in Finder
Finder/Applications/Utilities/Applications

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Finder, Go menu.
N/A
N/A
N/A
/Applications

Disk Utility
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New Stuff to Check Out
The only way to become truly proficient supporting an operating system is to use it. Be
sure to become familiar with the following new & improved features:
User Interface
1. The Dock
2. The Apple menu
3. System Preferences (Apple menu)
4. Dock preferences (Apple menu)
5. Force Quit (Apple menu)
6. Customize Toolbar (Finder/View menu)

System Preferences
7. Classic System Preferences
8. Dock System Preferences
9. International System Preferences
10. Internet System Preferences
11. Login System Preferences
12. Network System Preferences
13. Screen Saver System Preferences
14. Sharing System Preferences
15. Users System Preferences/Applications
16. Address Book
17. Chess
18. Clock19. Dock Extras
20. Image Capture
21. Preview/Applications/Utilities
22. Applet Launcher
23. Console
24. CPU Monitor
25. DigitalColor Meter
26. Directory Setup
27. Disk Utility
28. Display Calibrator
29. Grab
30. NetInfo Manager
31. Network Utility
32. Print Center
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34. Terminal

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Review Questions
Operating Systems 101
1. What kind of limitations do cooperative multitasking put on the user experience?
2. What advantages do protected memory offer the user experience?
3. What advantages do pre-emptive multitasking offer the user experience?
4. Will Mac OS X take advantage of multiple processors? How?
Components of Mac OS X
5. What are the two major components of Darwin?
6. Is declining to install BSD a good idea? Why?
7. How is Quartz different from QuickTime and OpenGL?
8. What is Quartz based on?
9. What kind of applications run directly in Mac OS X (as opposed to Classic)?
10. Can you install extensions and control panels in Classic and make them available toapplications running in Classic?
11. Does the Mac OS 9 System Folder used by Classic have to be on the same volume as
Mac OS X?
Useful Mac OS X Jargon
12. How do you peek inside a bundle?
13. How is a bundle different from a package?
14. What is a Framework analogous to in Mac OS 9?
Mac OS X Installation
15. What directory format should a user select?
16. Why is the Mac OS X Setup Assistant a Good Thing?
17. What keyboard sequence might a user use to watch system components load at
system startup?
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18. What goes into a Library folder?
19. What’s the difference between a user’s Applications folder and the system’s
Applications folder?
20. Can different users see each others’ Applications folders by default?
21. Where do user fonts go?
Security
22. What is a truly secure computer?
23. How many groups can a file belong to?
24. What’s the main difference between root and an Administrative user?
25. Where do you go to enable root access?
26. How do you ensure a login prompt is displayed after a simple restart?
Old Stuff in New Terms
27. What do you tell a user who wants to turn on desktop printing?
28. How would you troubleshoot a situation where command-shift-3 doesn’t perform ascreen capture?
29. How do you set startup items?
30. How do you troubleshoot extension conflicts?
31. Where do you go to enable AppleTalk?

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Review Answers
Operating Systems 101
1. What kind of limitations do cooperative multitasking put on the user experience?
Poorly behaved applications can take over the system, resulting in inconsistent or poor
performance.
2. What advantages do protected memory offer the user experience?
A process can crash without affecting other processes or the operating system.
3. What advantages do pre-emptive multitasking offer the user experience?
The user stays in control.
4. Will Mac OS X take advantage of multiple processors? How?
Mac OS X will take advantage of two processors, when available. It does so via
symmetric multiprocessing support (SMP). Individual applications can boost their multiprocessor component by utilizing multithreading.
Components of Mac OS X
5. What are the two major components of Darwin?
Mach and BSD.
6. Is declining to install BSD a good idea? Why?
No. You lose a number of network services.
7. How is Quartz different from QuickTime and OpenGL?
Quartz focuses on 2D imaging.
8. What is Quartz based on?
Adobe Portable Document Format.
9. What kind of applications run directly in Mac OS X (as opposed to Classic)?
Cocoa, Carbon or Java.
10. Can you install extensions and control panels in Classic and make them available toapplications running in Classic?
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Yes.
11. Does the Mac OS 9 System Folder used by Classic have to be on the same volume as
Mac OS X?
No.
Useful Mac OS X Jargon
12. How do you peek inside a bundle?
Hold down the Option key and click on the bundle.
13. How is a bundle different from a package?
Same thing.
14. What is a Framework analogous to in Mac OS 9?
Similar to a PowerPC shared library.
Mac OS X Installation
15. What directory format should a user select?
Mac OS Extended (HFS+).
16. Why is the Mac OS X Setup Assistant a Good Thing?
It helps ensure that networking services are correctly set up.
17. What keyboard sequence might a user use to watch system components load at
system startup?
Command-V.
18. What goes into a Library folder?
Data and preferences utilized by applications.
19. What’s the difference between a user’s Applications folder and the system’s
Applications folder?
A User’s applications are installed and used by that single user. The system’s
applications are available to all users.

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20. Can different users see each others’ Applications folders by default?
No.
21. Where do user fonts go?
/Users/myhome/Library/Fonts
Security
22. What is a truly secure computer?
Locked in a room and disconnected from a network.
23. How many groups can a file belong to?
One.
24. What’s the main difference between root and an Administrative user?
Root can introduce and remove files from the System folder.
25. Where do you go to enable root access?
Netinfo Manager.
26. How do you ensure a login prompt is displayed after a simple restart?
It’s an option in the Login System Preferences.
Old Stuff in New Terms
27. What do you tell a user who wants to turn on desktop printing?
Mac OS X does not support desktop printing. Check out the Print Center.
28. How would you troubleshoot a situation where command-shift-3 doesn’t perform ascreen capture?
Use the Grab utility instead.
29. How do you set startup items?
It’s an option in the Login System Preferences.
30. How do you troubleshoot extension conflicts?

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You don’t—there isn’t an equivalent of Mac OS 9 extensions.
31. Where do you go to enable AppleTalk?
Network System Preferences.

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Further Reading
UNIX System Architecture
McKusick, et. al. The Design and Implementation of the 4.4 BSD Operating System.
Boston: Addison-Wesley, 1996
Bach, M.J. The Design of the UNIX Operating System. Englewood Cliffs: Prentice
Hall, 1986.
Wood, P. H. et. al. UNIX System Security. Indianapolis: Hayden Books, 1988
Silberschatz et al, Operating Systems Concepts, Fourth Edition.

Darwin Information
http://www.darwinfo.com
Unofficial site hosting a number of patches, ports, and an exhaustive FAQ.
http://www.opensource.apple.com/
Official home page for Darwin information.

Mac OS X General Info Sources
http://www.apple.com/macosx
The Mac OS X home page.
Mac OS X System Architecture
http://developer.apple.com/techpubs/macosx/SystemOverview/SystemOverview.pdf
An awesome high-level overview of how Mac OS X works.
http://developer.apple.com/techpubs/macosx/Kernel/KernelEnvironment/KernelEnviron
ment.pdf
A low-level overview of how the innards of Mac OS X works.
http://www.mit.edu/people/wsanchez/papers/USENIX_2000/
Discussion of the challenges involved in grafting UNIX with Mac OS.

Mac OS X Developer Information
http://developer.apple.com/macosx/
General information.
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39http://developer.apple.com/techpubs/macosx/macosx.html
Technical publications.

General UNIX Texts
Abrahams et al, UNIX for the Impatient, Second Edition
Sobell, M. G., A Practical Guide to the UNIX System, Third edition.

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