How to Install macOS Sonoma on an External Drive for iPhone Development

Are you an iPhone developer looking to install macOS Sonoma on an external drive? Look no further! While Apple may not officially support installing macOS on an external drive, it is possible with some creative workarounds.

Firstly, let's clarify that the 'Use more than one version of macOS on a Mac' page linked in point 1 specifies that you need to create a new volume on your startup disk. This can be confusing, but we'll get to that later.

Method 1: Using the Ventura Installer

To install macOS Sonoma on an external drive using the Ventura installer, follow these steps:

1. Partition your external drive with a GUID partition table and create a small 'Mac OS Extended' partition and a large APFS partition.

2. Use the createinstallmedia tool to put the installer on the small 'Mac OS Extended' partition.

3. Boot into the installer by restarting your Mac while holding down the power button, then select the external drive with the new installation from the boot menu.

However, when you try to install macOS Sonoma, you may encounter issues where the spinner appears for a second and then nothing happens.

Method 2: Using Createinstallmedia

An alternative approach is to use createinstallmedia to put the installer on the small 'Mac OS Extended' partition. This method also has its limitations, as it may not work seamlessly with all devices.

To use createinstallmedia:

1. Partition your external drive with a GUID partition table and create a small 'Mac OS Extended' partition and a large APFS partition.

2. Use createinstallmedia to put the installer on the small 'Mac OS Extended' partition.

3. Boot into the installer by restarting your Mac while holding down the power button, then select the external drive with the new installation from the boot menu.

Unfortunately, this method may also result in the same issue where the spinner appears for a second and then nothing happens.

Getting macOS Sonoma

To get the latest macOS Sonoma Developer beta, follow these steps:

1. Go to System Settings > General > Software Update.

2. Click the info button next to Beta updates.

The macOS Sonoma update is compatible with MacBook Pro models from 2018 onwards, so you won't need to buy Apple's best Macs just to run it.

While installing macOS Sonoma on an external drive may be a bit tricky, it is possible with some creative workarounds. By following the steps outlined above, you should be able to install macOS Sonoma on your external drive and enjoy developing for iPhone without needing to buy Apple's best Macs.

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