We do not insist upon the full "goat-sacrifice" approach to updates. Some people recommend rather elaborate procedures: back up before updating; both before and after updating, clear caches, repair permissions, and run DiskWarrior; and so forth. None of this is likely to do any harm, but if updating is made overly complicated, users won't do it at all or, even worse, will just be confused.
On the other hand, it is reasonable to accept the premise that Apple's Software Update, as presently implemented, is inherently dangerous. An application is going to download important system components and replace my existing components with them, while I'm actually using the computer? You've got to be kidding! In fact, the goal during system component installation should be just the opposite, namely, to minimize use of the computer during installation.
Based on that premise, here are is a simple, minimalist procedure for performing system updates.
[Note: This procedure cannot guarantee that a system update will not break, or appear to break, some functionality of your computer. System updates can be badly written; and even when they are well written, computers are complicated, and Apple can't predict every possible contingency and configuration.]
- General principles.
- Leave all Apple-installed components where they are. Don't, for example, move Safari out of /Applications, or move your user Home folder.
- In System Preferences > Software Update, make certain that "Download important updates in the background" is not checked. If your computer has multiple users, do this for every user. It might also be wise to uncheck "Check for updates"; one user, the administrator, should then be responsible for checking manually for updates from time to time. (To do so, choose Apple > Software Update.)
- When an update is available in Software Update, do not press the Install button in the Software Update window. Instead, download any desired update packages individually and without actually performing the installation. Software Update allows you to do so, but this feature is not at all obvious, so here are instructions:
- Make sure there is a checkmark at the left of all and only the packages you want to download.
- Choose Update > Download Only. After performing the download(s), note the location, on your hard drive, of the downloaded material.
- Restart into Safe mode, by holding down the Shift key from the moment you hear the startup "bong" to the moment the "spinning gear" appears. Expect this startup to take longer than usual. Don't be alarmed if the fans whir loudly during the "spinning gear" display. Eventually you will be presented with the Safe Boot login screen. Log in as the administrator.
- Without launching any other applications, double-click one installer package and perform the installation. Do nothing else; just sit there and wait until the installation is complete.
- Repeat step 3 after every installation. Finally, restart normally. This, too, may take longer than usual, and you may experience a "double-restart." Be patient!