Reference 4.2 Manually Install Updates
Before the Mac App Store or automatic software updates, all Mac software was acquired and installed manually. Fortunately, OS X has always featured relatively simple software installation. In fact, many applications require only that the user copy a single application file to the local Applications folder. On the other hand, more complex software may require multiple resources to be placed in a variety of specific locations on your Mac.
A prime example of a complicated software installation is any system software update. In some cases it may be more convenient to manually install an update, as opposed to using automatic software update via the Mac App Store. For example, perhaps you need to install a particularly large software update for a system with limited Internet bandwidth. It may be better to manually download the update to a portable flash disk at a location with more bandwidth and then use the flash disk to apply the update to the Mac that needs it. An experienced OS X support specialist will always have an external disk with the most common large updates handy for just such an occasion.
The Installer application makes complicated application installations simple. Often, software developers will create an “installer package” with all the instructions and resources necessary for the Installer application to set up the new software on your system.
Double-clicking one of these software installer packages opens the Installer application and begins the installation process. Much like the OS X installation process, the Installer application guides you through the steps necessary to install or update software. This may include agreeing to software licenses, selecting a destination, selecting package options, and authenticating as an administrative user.
Unlike the Mac App Store, the Installer application requires administrative access to install many items. This security mechanism is in place because anyone is allowed to make and distribute traditional OS X installer packages, including those who may have nefarious goals. Another mechanism in OS X, known as Gatekeeper, also provides an additional level of protection against unknown installation packages and software. You can find out more about Gatekeeper in Lesson 16, “Install Applications.”
Advanced Installer Features
If you’re curious about what an installation package is actually doing to your Mac, you have two ways to find out. First, you can view the Installer log at any time while using the Installer application by choosing Window > Installer Log or pressing Command-L. The Installer log is a live view of any progress or errors reported during the installation process.
The second method allows you to inspect the contents of an installer package before installation. After opening an installer package in the Installer application and passing the initial welcome and license screens, you can preview the list of files to be installed by choosing File > Show Files or pressing Command-I.
Apple has endeavored to increase the security and reliability of software installation packages by supporting signed packages. These packages contain special code used to validate the authenticity and completeness of the software during installation. This makes it nearly impossible for malicious parties to insert illegitimate files in trusted installation packages. You can recognize a signed installer package by the small lock icon in the far right of the installer window title bar. Clicking this icon displays details about the signed package, including its certificate status.