The macOS installer is efficient and user-friendly, but there is more to learn about the installation process by examining the built-in logs. macOS installer files, known as Packages, typically end with a .pkg extension. When a .pkg file is opened to install software on a Mac, Apple’s installer app undergoes various steps to validate and install the software. These steps usually involve verifying the package, decompressing payloads, copying them to the target drive, and running post-install scripts for final checks and cleanup.
While the installation process may appear simple on the surface, there is a lot happening behind the scenes. Fortunately, the installer maintains a detailed log of the installation process that can be easily viewed, saved as a text file, or printed. Most .pkg files do not contain an installer app; instead, they are read and executed by macOS’s installer app (Installer.app) located in /System/Library/Core Services on the Startup Disk.
To access a list of all .pkg files on your Mac, press Command-F, set the search terms to “Kind is Other,” and enter “Installer” in the search field. .pkg files are considered Bundles in macOS, similar to app bundles. Custom installers created by developers may also exist, running independently of Installer.app.
Starting from macOS X 10.5 Leopard, Apple introduced the ability for developers to create flat installer package files. These files are single encoded, have a .pkg extension, and are managed by Installer.app. Flat file packages prevent users from inspecting their contents using Finder’s “Show Package Contents” feature or Terminal. When opened, Installer.app executes the contents of the .pkg file.
If a .pkg file is not a flat file package, you can Control-click on it in Finder and select “Show Package Contents” to view its contents. It is advised not to modify the contents of a .pkg file, as many .pkgs include digital signing information that must match the package’s contents.
After an installation, macOS appends a summary of the installation to a file called “InstallHistory.plist” stored in /Library/Receipts on the Startup Disk. This file is in a plist format and contains details about the installation, including a list of bundle IDs associated with the installed packages.
To view the system-wide log file “install.log” on macOS, go to /private/var/log on the Startup Disk. This file can be viewed using any plain text editor. The Console app in /Applications/Utilities on the Startup Disk allows you to view and manage system logs, including install.log.
Additionally, macOS includes a command-line tool named “pkgutil,” which is a versatile .pkg utility. By typing “man pkgutil” in Terminal, you can access instructions and options for using pkgutil. Some useful operations provided by pkgutil include listing installed package IDs, displaying installed files, showing metadata about a package, and more.
It is possible to delete certain log files from /private/var/log on your Mac, but be cautious not to delete essential or locked log files. Archived log files in .gz or .bz2 format can also be removed if not needed. You can delete logs from the Console app as well, but an admin password is required.
In summary, macOS installer logs and utilities offer valuable insights into the installation process and system operations. Understanding these logs can help troubleshoot installation errors and ensure a smooth software installation experience on your Mac.