How to install macOS 14 Sonoma or 13 Ventura on an external partition

I would like to install macOS 14 Sonoma on an external partition, but I couldn't find an installer on the developer website. It seems that it's only possible to upgrade from the System Settings, so I thought I would install Ventura first on the separate partition and then upgrade to Sonoma.

I downloaded the Ventura installer from the App Store and selected the external partition during the installation, but when the Mac reboots, it just reboots into my main macOS partition. If I shut down and hold the power button pressed to select the boot partition (I have a M1 MacBook Pro 14" 2022), then nothing happens: an indeterminate progress indicator spins for a couple seconds, the partition list remains there and I can only successfully boot into my main partition again. I also tried running the installer from another macOS Ventura and macOS Monterey partition I had installed last year, but when I select the partition on which to install the new Ventura, nothing happens and I can only quit the installer.

Is there a way to debug all these issues? How can I install macOS Sonoma on a separate partition without overwriting my main macOS Ventura install?

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Nickkk
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I would like to install macOS 14 Sonoma on an external partition

Me too!

I couldn't find an installer on the developer website.

I downloaded the .ipsw "restore image" from https://developer.apple.com/download/ but I don't know what to do with it!

In Disk Utility I can select my external disk and click "restore", and there is an "image" button, but the .ipsw file is not selectable in the file picker.

Is this one of those things where you have to hold down shift while clicking a button and a load of extra choices appear?

Someone must know how to do this....

Posted by
endecotp
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  • I think the ipsw just enrolls your mac into the beta so it can download the beta from the settings "software update". This is a new way that Apple introduced to download the beta on macs (which is kind of how they've been doing it with ios/ipados), but it will install over your current installation.

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    Odysseus42
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I have the same exact issue. I called Apple support, but they ended up telling me that it's not a supported configuration and if it doesn't work there is nothing else they can do. It's very unfortunate. This worked fine on my Intel Macbook Pro. I hope it's just a bug in Ventura and it will get patched. Annoyingly, we can no longer even install a previous macOS version, and even if we do get an older macOS version, it won't boot on an Apple CPU mac with a newer macOS version. How are folks testing different macOS versions? Do you have to get several macs now?

https://discussions.apple.com/thread/254921596

Posted by
Odysseus42
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  • you can install a second version of Ventura on a partition then upgraded that version to Sonoma: https://apps.apple.com/es/app/macos-ventura/id1638787999?mt=12

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    kuba.libre

  • Yes, that could be an option, though a kind of painful one. I would have to repartition my drive and reinstall everything. In any case, I got the USB-C drive to work. I was about to purchase a Thunderbolt drive to test with that, but turns out I don't have to. Details in the discussions.apple.com thread link I provided

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    Odysseus42

  • Did you just download the Ventura installer and ran it? Because as I wrote in the original post, I wasn't able to install Ventura either.

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    Nickkk

Did you just download the Ventura installer and ran it? Because as I wrote in the original post, I wasn't able to install Ventura either.

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Nickkk
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I was doing installs from the Ventura download and the recovery partition. My last attempt was via the recovery partition. I can’t see why it would matter, but this certainly seems like a bug, so who knows

Posted by
Odysseus42
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  • I tried reinstalling Ventura on my external partition from the recovery one and it seemed to prepare the installation just fine, but then it rebooted into my main Ventura partition. Selecting the newly created Ventura partition from the startup disks makes the indeterminate progress indicator spin for a couple seconds, then it disappears again and nothing happens, just like when installing Ventura with the dmg installer. In my case, installing Ventura or Sonoma seems impossible.

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    Nickkk
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