How to Dual Boot two versions of Mac OS

Question

How to Dual Boot two versions of Mac OS

In descriptions of Dual Booting one is given a picture of a choice of destination between two Volumes, one, the original Mac HD and the other, a constructed volume defined by addition by Disk Utility. This is conceptually straight forward. However what is never mentioned is how one gets access to a clean operating system version that is not encumbered with a predestination to be an upgrade to the resident os already on the Mac HD original volume. I am running an i7 Mac Mini with Mojave 10.14.6 and I want to dual boot up in the second volume a clean version of Catalina or possibly Big Sur. Finding one or the other of those installer packages not predestined to be an upgrade to Mojave has eluded me. It appears impossible but I am hoping someone knows differently.

Thanks for your attention

RAZ

Mac mini, macOS 10.14

Posted on Nov 28, 2020 3:09 PM

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Answer 1

Best reply

Niel

Level 10

727,433 points

Nov 28, 2020 3:12 PM in response to raymondzachary

To install the second OS, download it normally, but change the target volume when setting up the installation.

To boot into the second OS, select it in the Startup Disk pane of System Preferences.

(187050)

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Answer 2

Nov 28, 2020 6:36 PM in response to Niel

The problem is that downloading the second OS normally inevitably means it will be tagged as an upgrade to Mojave and not a free standing OS. Therefore it can only be applied to the Mojave Volume.

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Answer 3

Niel

Level 10

727,433 points

Nov 28, 2020 6:47 PM in response to raymondzachary

All of the Mac App Store OS downloads are full installers, not updaters; you'll be given the option to choose a different volume.

(187062)

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How to Dual Boot two versions of Mac OS

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