This article provides guidance on using Munki to perform in-place macOS upgrades on Intel hardware without disturbing user data.
Looking to instead perform a clean macOS install? Here's how.
Munki Mac Endpoint Management
University of Illinois IT Pros leveraging Technology Services Endpoint Service Munki Mac Endpoint Management
Multi-Tenant Munki can be used to perform in-place macOS upgrades (e.g. from macOS 10.15 to macOS 12) on Intel hardware without disturbing user data. These upgrades use Apple's own 'startosinstall' upgrade mechanism built into macOS installer packages, ensuring that any required firmware updates are applied during the upgrade.
Due to volume ownership requirements, Munki may not be used to upgrade Apple Silicon hardware.
Upgrade packages for macOS 12 (Monterey--Intel only), macOS 11 (Big Sur--Intel only), and macOS 10.15 (Catalina) are available for MTM stakeholder use. The upgrade installer name keys are install_macos_[monterey/big_sur/catalina].
Before planning an OS upgrade, check Apple's system requirements to confirm hardware compatibility. Munki can't natively know if the device in question is capable of running the new operating system, so it will try in all cases but fail on unsupported hardware.
Next, check vendor resources to confirm that all vital software on the device is compatible with the new OS.
When ready, make the upgrade available by adding it to the Mac's serial number manifest as either an optional install or a managed install. (See our article on Munki manifests for guidance on editing manifests.)
As indicated in Managed Software Center, OS upgrades (whether optional or managed) do require a restart and a wired connection (as most wifi connections do not persist after logout), and may take up to several hours to complete, depending on the age of the hardware and the type of hard drive. Upgrades on SSDs will take considerably less time to complete. As with any macOS upgrade, there is always a possibility that the upgrade process may hang, become caught in a restart loop, or otherwise fail to succeed. For this reason, it's best to schedule upgrades when the Mac is on campus, or when it can be brought to campus if post-upgrade support is required.