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Selectively Installing Mac OS X Files

Suppose at some point you accidentally delete an application that is included as part of Mac OS X or that came preinstalled on your drive. Or perhaps the application somehow gets corrupted and no longer launches. Even worse, you never made a backup copy of it. What can you do? You have several choices.

Do a Custom Install/Restore

A Custom Install ideally allows you to reinstall just the software you want, without having to do a complete reinstall of Mac OS X. With a complete reinstall, you run the risk of overwriting a file (possible a newer version of the file) that you don't want to modify—not to mention the fact that you're reinstalling thousands of perfectly OK files to get the one file that's missing (or not OK). As always, exactly how to do a Custom Install varies as a function of the Mac model you have.

To do a Custom Install on Macs that come with an Install DVD that includes an Install Bundled Software Only icon, start by double-clicking this icon. When you get to the Installation Type pane, click the Customize button. From here, you will be able to select which applications you want to reinstall. If the software you want is not listed, quit the Installer and instead double-click the Install Mac OS X and Bundled Software icon. Restart your Mac when requested and similarly check the Customize options.

Alternatively, you may be able to locate and launch a specific desired .pkg file (such as iPhoto.pkg) from an Install/Restore disc that allows you to install just the particular software you want. To find most of the packages you might want, go to /System/Installation/Packages on the initial Install 1 DVD.

Note: Some package items are in an invisible folder called .packages located inside the Packages folder(s). To see these items, use a utility such as InVisibles to make invisible items visible. Or use the Finder's Go to Folder command and type the path to the desired folder. For example, for the Install Disc 1 DVD, you would type /Volumes/Mac OS X Install Disc 1/System/Installation/Packages/.packages. Installing from an application's .pkg file is almost the same as installing the software via a Custom Install from the "full" Mac OS X Installer. One advantage of the separate install is that you may not need to restart your Mac from the Install disc in order to install. Also, you may be able to locate and install a .pkg file that is not listed separately in the Customize pane of the full Installer.

Note: In some cases, a .pkg file (especially an .mpkg file) may serve only to redirect the Installer to other .pkg file(s) where the software is actually located.

Note: If you install a version of an application from your Mac OS X Install disc, and a later update to Mac OS X—or just to that application—had previously updated the application, you'll need to go back and reinstall the update(s) to make sure you've got the latest version of the application.


Figure 3.11 The/System/Installation/Packages folder on a Mac OS X Install Disc.

Copying from the Mac OS X Install discs

If the latest version of the file you want is on the Mac OS X Install discs, as an accessible file, you can copy it directly from the disc.

On some Install Disc 1 discs, for example, check inside the System folder at the root level of the disc. Here you will find a Library folder that contains copies of some files (such as Fonts) that eventually get installed in /System/Library on your drive. Should you need to replace one of these files (perhaps because you tried a hack on one of the files, and it failed and you don't have a backup), you can use the copy here. One caution: Occasionally, a file used on an Install disc will differ from that used on a hard drive. Overall I would be cautious about using this method and recommend performing a Custom Install instead.

The /Applications/Utilities folder contains working copies of applications such as Disk Utility and Installer.

Reinstalling from a Web download

If you cannot or do not wish to reinstall software from the Install disc(s), you may be able to download a separate installer from the Web. Check Apple's Web site to see if one is available.

Extracting from an expanded .pax.gz file

If the file you want is contained within a .pkg file—for example, MacOSXUpdateCombo10.4.3.pkg—you will most likely need to extract the file from the larger update. Here's one way to do so:

  1. Locate the .pax.gz file (for example, Archive.pax.gz) inside the Installer package file. (To view the contents of the package file, Control-click it and then select Show Package Contents from the menu that appears; then open the Contents folder.)
  2. Make a copy of the .pax.gz file and move it to the Desktop. (Although this step is not required, it serves as a good precaution against damaging the only copy.)
  3. Decompress the copied file. If the current version of StuffIt Expander does not decompress the file, use the shareware application OpenUp, by Scott Anguish ( For large update packages, expect this output to take up a healthy amount of disk space (since it contains every file in the update).
  4. Locate the desired file and use it to replace the original. You may need root access to do this. You can delete the remaining expanded files or save them in case you need to do this again someday.

Figure 3.12 Top, inside the package file of a Keynote Updater; bottom, the receipt file for the same updater. Note that the .pax.gz file is missing from the receipt file.


Figure 3.13 This Pacifist window displays the contents of a Tiger Mac OS X update file. Clicking the disclosure triangles reveals subdirectory contents.

Use Pacifist

A simpler (and thus better) alternative to the previous procedure is to use a shareware utility called Pacifist, by CharlesSoft ( Simply open a package (.pkg or .mpkg) file from within Pacifist, and you will see a complete list of all files in the .pkg file. You can then choose to extract a single file (or more, if you wish)—either to its intended destination location or to any location you select.

Note: On the Mac OS X Install CD, most of the to-be-installed software is stored in .pkg files. For example, inside the System folder at the root level of the CD is a folder called Package, which contains several .pkg files (most notably Essentials.pkg) that include the bulk of the Mac OS X software. You can open these packages via Pacifist to extract individual files. In fact, Pacifist has an Open Mac OS X Install Packages button that will provide a list of all packages on a Mac OS X Install disc along with the contents of each.

Of course, if you have a newer version of Mac OS X installed on your hard drive than the version on the Install CD, check any Update .pkg file(s) you have to see if there is a newer version of the software than the version on the Install CD—unless you specifically intend to downgrade as part of some troubleshooting work-around (in which case you want the version on the Install CD).

Cautions regarding extracting files from update packages

Two cautions about using Pacifist or otherwise extracting software from a .pax.gz file:

  • Related files may not get extracted. Sometimes the software you want to replace is part of a related set of files. For example, an application may require a file in an Application Support folder and/or an update to a Framework in order to function correctly. In such cases, if the additional files are not already present on your drive, just installing the application may not be sufficient. A complete reinstall of Mac OS X then becomes a better choice. You will know this is a possibility if the application does not work after the installation.
  • The extracted file may be incomplete. Starting with Mac OS X 10.3.4, Apple began releasing three different versions of most OS updates: Combo, Delta, and Patch.

    Combo updates contain all the changes made, from the original major version of the OS to the most recent minor update. For example, the Mac OS X 10.4.3 Combo Update can update any version of Mac OS X 10.4, from 10.4.0 to 10.4.2.

    Delta updates typically contain only the changes from the immediately previous version. For example, the Mac OS X 10.4.3 Update can only update systems running Mac OS X 10.4.2.

    Patch updates are similar to Delta updates. However, to keep the size of the update .pkg file to a minimum, they typically include only those files within application packages (and any other bundles) that have been modified in the update. Thus, a patch update that contains a new version of Safari may only include the files in the Safari package that have been changed. The extracted Safari application package would thus be incomplete and would not run.

    Patch updates can be used only by certain installations of the previous update. They are only available as a download via Software Update because Software Update must first see if your installation of Mac OS X is eligible to use the Patch version. Because a Patch version of an update does not contain complete versions of most software, you should not use a utility such as Pacifist to extract parts of the update.

    You can see if an update package you've downloaded is a Patch version by looking at its name—if so, the name will end in Patch.pkg.

I would hesitate to use Pacifist to extract files from anything but a Combo update package or, even better, a full Mac OS X Installer package.

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