Installing Mac OS X Applications

Although Carbonized and Cocoa applications behave somewhat differently, their similarities are at least as great as their differences. This is especially true when it comes to the installation of applications.

Under Mac OS X, there are two basic strategies by which applications are installed:

  • Drag and drop Under this method, you simply drag the application files from one location to the location in which you want to install them.

  • Installer Some applications use an installation program to install the application and related files for you. Most applications use the standard Mac OS X Installation application as their installation mechanism.

Because Mac OS X is designed as a multiuser OS, where you install Mac OS X applications is a bit more complicated than was installing applications under previous versions of the OS. There are two locations in which you should install Mac OS X applications:

  • Applications directory If you want the application to be accessible to all users of your Mac, you should install it in the Applications directory. To be able to do this, you must be logged in as an administrator. Most applications that use an installer will be installed in the Applications directory, and you usually don't have the option to install them elsewhere.

  • The Home directory You can sometimes install applications in a user's Home directory (primarily applications that have drag-and-drop installation). You should install applications in a user's Home directory only if you don't want everyone who uses your Mac to be able to use that application.


Accessing an application installed in a Home directory is dependent on the permissions you assign to that application's folder. Modifying the permissions of the application's folder so that all users have access will allow everyone to use the application, even if they are not logged in as the user that owns that application.

These installation locations are appropriate only for Mac OS X (Carbonized or Cocoa) applications. You install Classic or Unix applications in locations that are appropriate for those types of applications.


If you have trouble installing an application, make sure that you are logged in as an Administrator. Many application installations can be done only while using an Administrator account.

Installing Mac OS X Applications with Drag and Drop

Under Mac OS X, applications can be provided as bundles. A bundle is the collection of the executable files and other resources that are required for an application. An application bundle can be presented to you as a single icon; this makes the drag-and-drop installation technique possible. Instead of having to deal with an installer application or with a bunch of individual files, you can easily act on an entire application bundle by acting on its single icon.

Installing applications that use the drag-and-drop method is especially simple. Most of these applications are provided as Self Mounting Image (.smi) or Disk Image (.dmg) files. This means that the file behaves just as if it were a volume you mount on your desktop. This is accomplished through Apple's Disk Copy application, which will handle .smi and .dmg files for you automatically.

Most of the Mac OS X applications you will install use this method, making installation of Mac OS X applications almost trivially easy.


The only difference between the behavior of .smi and .dmg files is that .smi files automatically mount on your desktop when you launch them. Disk image files use Apple's Disk Copy software to mount?because this application is installed on your Mac by default, these files behave quite similarly and you probably won't notice any difference between them. However, you could use an .smi file even if Disk Copy wasn't installed on your machine, whereas you can't use a .dmg file without the Disk Copy application.

The general process to install an application provided in an .smi or .dmg file is the following:

  1. Download and uncompress the .smi or .dmg file.

  2. Double-click the .smi or .dmg file. Its volume will be mounted on your desktop, just as a removable disk such as a CD or a hard drive.

  3. Open the resulting volume and drag the application's folder or file to the appropriate directory on your Mac.

  4. Unmount the mounted volume by selecting it and pressing graphics/symbol.gif+E (or choose File, Eject).

  5. Discard the .smi or .dmg files or keep them in case you need to install the application again.

To learn how to download files from the Web and prepare them for use, see "Downloading and Preparing Files," p. 345.


Some applications don't even provide a .smi or .dmg file. After you download and uncompress the file, you will have the application's folder immediately. Drag this folder to where you want the application to be installed.

Most Apple applications that you can download from the Web are provided in the .smi format, as are many third-party applications. As an example, download and install OmniWeb, which is a popular Mac OS X Web browser.

  1. Log in as the Administrator for your Mac.

  2. Go to

  3. Download OmniWeb. After the file is downloaded, it will be uncompressed and decoded automatically. When the process is complete, you will see the OmniWeb.dmg file.

    To learn how to download files from the Web and prepare them for use, see "Downloading and Preparing Files," p. 345.

  4. Open the OmniWeb.dmg. Disk Copy will open and you will see the license agreement for OmniWeb.

  5. Click Agree. The OmniWeb volume will be mounted on your desktop.

  6. Open the volume and you will see the OmniWeb package file (see Figure 6.1).

    Figure 6.1. On this desktop, you can see the OmniWeb volume open in a Finder window and the contents of that volume, which is one file.


  7. Drag the OmniWeb icon into the Applications directory to copy it there.


    The fastest way to open the Applications directory is to press Option+graphics/symbol.gif+A.

  8. Drag the OmniWeb volume to the Trash to unmount it or press graphics/symbol.gif+E to eject it.

  9. Launch OmniWeb to see how it looks.



OmniWeb is produced by The Omni Group whose Web site is

After you have installed the application, you can delete the .dmg file. However, you might want to create a directory to store these files in the event that you need to reinstall the application at a later date. This will prevent you from having to download it again.


If you aren't able to place the application in the appropriate directory, see "I Can't Install an Application Because I Don't Have Sufficient Privileges" in the Troubleshooting section at the end of this chapter.

Installing Mac OS X Applications Using an Installer

Most applications that use an installer application install in a similar fashion; however, minor variations can exist depending on the specific installer application that is used.

Under Mac OS X, most applications that use the Installer application come in package files, which have the extension .pkg. And most Mac OS X applications use Apple's Installer program. For example, when you installed Mac OS X on your machine, you used this installer.


When you download an application that comes in a .pkg file, it will often be included in a .dmg or .smi file. This usually is done when there are files outside the application to be installed that the developer wants to include with the application, but that should not be installed as part of it (readme files, for example).

The general process to install and use .pkg files is the following:

  1. Download and prepare the file containing the application you want to install.

  2. Mount the disk image and open it.

  3. Double-click the .pkg file.

  4. Work through the steps in the installer application.

An example of an application that uses this technique is the Samba Unix server application, which enables you to share files with Windows users.

  1. Log in as the Administrator for your Mac.

  2. Go to and search for Samba for Mac OS X.

  3. Download and uncompress the Samba for Mac OS X file. You will see the Samba for Mac OS X 2.2.2.dmg file.

  4. Open the disk image.

  5. Open the package file, which is samba.pkg. You will see the Installer window. Just as when you installed Mac OS X, the left pane shows you the steps you will work through using the installer. The right pane provides you with information about each step. At various times, you also see the Close and Go Back buttons.

  6. Verify that you are the Administrator by clicking the Lock icon and entering the Administrator password.


    Some installations require that you authenticate yourself as an Administrator before you can begin to do the installation?even if you are already logged in as the Administrator.

  7. Continue working through the steps in the installer until you get to the screen that tells you that the software was successfully installed (see Figure 6.2).

    Figure 6.2. Applications that use Mac OS X's Installer application to install will look very familiar to you because this is the same installer you used to install Mac OS X.


  8. Click Close to quit the Installer application.


If Classic launches when you run an application's installer application, but the installer has problems, see "I Can't Install an Application Because I Am Having Problems with Classic" in the Troubleshooting section at the end of this chapter.

    Part I: Mac OS X: Exploring the Core
    Part III: Mac OS X: Living the Digital Lifestyle