How Software Update settings obtains a list of available updates, and the variants that should contain. How mobile asset catalogues are checked, and preparations made to download the update.
Software Update
How SilentKnight came about, and how it knows – most of the time – which version of XProtect and other security data your Mac should be using.
What to do when you know there’s an update available, but Software Update pretends that it can’t find it. With details of undocumented options for softwareupdate command and more.
Software update was completely redesigned for Big Sur, using finite state machines to enable reliable, flexible and robust updates to be applied to macOS. These are documented in log entries made during an update.
How macOS 26.2 updated to 26.3, variation in download sizes, how macOS works out free space requirements to proceed with the update, and its sequence of stages run by a finite state machine.
When the architecture of macOS switched to the Signed System Volume in Big Sur, it brought major changes in how macOS is updated, as detailed here.
Want to stay running Sequoia or earlier? Want to install security updates such as XProtect data as well? Here’s how to do that without risking being upgraded unintentionally.
Until Sequoia, it was simply downloaded and installed as any other software update. Since then it has changed frequently and its behaviour can now confuse.
Originally two separate services in Mac OS X Server, for Software Updates and later Content, it reached client versions of macOS in High Sierra in 2017.
Users should be given a third option to defer updating further, as well as doing it now or later tonight. Does the DAS scheduling and dispatch system rely on security through obscurity too?
The Eclectic Light Company 