- In This Chapter
- What You Need to Install and Run Mac OS X
- Installing or Reinstalling Mac OS X
- Restoring Mac OS Software
- What About Mac OS 9?
- Selectively Installing Mac OS X Files
- Upgrading Mac OS X
- Updating Mac OS X
- Downgrading and Re-upgrading Mac OS X
- Uninstalling Mac OS X
- Understanding Image, Installer Package, and Receipt Files
- Backing Up and Restoring Mac OS X Volumes
- Creating an Emergency Startup Volume
- Troubleshooting Tips and Hints: Installing Software
Downgrading and Re-upgrading Mac OS X
Occasionally (though hopefully not often), you may decide that you need to downgrade to an older version of Mac OS X—perhaps due to a bug in the latest update.
Similarly, you may sometimes need to start over with a fresh installation of Mac OS X. Most likely, you will want to attempt this when you begin to have general problems running Mac OS X for which you can find no easier solution. In most cases, doing this means downgrading to an older version of Mac OS X and then re-upgrading back to the current version.
Archive and Install, then re-upgrade
The best way to handle downgrades and re-upgrades is to start with a complete reinstall of Mac OS X, using the Installer's Archive and Install feature, which you can access when starting up from a Mac OS X Install disc. If your Install disc doesn't include this feature, you should erase your entire volume and reinstall from whatever Install disc you do have.
Note: You cannot do a direct downgrade from Apple's Installer, even for a minor upgrade. For example, if you tried to install Mac OS X 10.4.1 on a volume running 10.4.2, the Installer would not allow it.
After doing an Archive and Install from the Install disc, you will likely be back at an older version of Mac OS X than the one you were previously running (for example, you may be back at 10.4.0, when you had been running 10.4.3).
To re-update to the current version of Mac OS X, use Software Update; it automatically lists the needed update(s). Software Update should also list any updates beyond Mac OS X itself that you may need to reinstall as a result of the Archive and Install—and allow you to install them all in one step (while you leave to have lunch!).
Alternatively, assuming you want to re-update to the latest version of the OS, download the most recent Combo Mac OS X updater (as described in "Updating Mac OS X," earlier in this chapter) from Apple's Web site. Not only is using the Combo updater simpler and faster than downloading and installing multiple individual Mac OS X updates, but it's also more likely to remedy whatever symptom led to your decision to reinstall.
The main advantage of using a Web download rather than Software Update is that if you don't wish to return to your current version (perhaps you were running Mac OS X 10.4.3 but now want to downgrade to 10.4.2), you can do so by selecting the appropriate update file from the Web.
Of course, you cannot downgrade "lower" than the version installed by the Install disc. Thus, if you want to downgrade from Tiger back to Panther, you would need to use a Panther Install disc.
Warning: If you do an Archive and Install of an earlier major Mac OS X version (for example, 10.3) over a newer major version (for example, 10.4) preserving user and network settings, you may not even be able to log in. The work-around is to not preserve user and network settings. In addition, Apple has documented (at http://docs.info.apple.com/article.html?artnum=25508) an issue where "downgrading" in this manner may result in applications' not opening documents, unexpectedly quitting, or refusing to launch at all. Their "fix" is to re-update back to the version of Mac OS X you were running prior to the Archive and Install—which, of course, defeats this particular purpose for doing an Archive and Install—or to at least update affected applications to the latest versions.