I made two full clones to different containers on my external SSD: one was from my internal SSD, the other from a Thunderbolt 3 external disk which already has a fully functional and bootable copy of Big Sur 11.3.1 installed on it. When you then click on the button to Start that full clone backup, there are subtle differences in what’s shown in CCC’s window. Click on the button to Allow CCC to erase. Select this by clicking on the destination volume and choosing the Legacy Bootable Backup Assistant…ĬCC then explains the implications of this option. You could perhaps then install Big Sur into that volume group, but I opted to use what CCC terms its Legacy Bootable Backup option. If you then make a regular clone to one of those containers from a bootable volume group using Carbon Copy Cloner 6, the default is to omit the System volume. I prepared my external SATA/USB-C SSD by connecting it to a USB-A port on my M1 Mac mini, which I know works reliably for booting, then using Disk Utility to divide it into a series of 100 GB containers, each of which will contain a different version of Big Sur.

The alternative is to keep old versions in Virtual Machines in Parallels Desktop. SATA/USB-C disks may need to be connected to a USB-A port rather than USB-C. Some external disks can only boot when physically connected in certain ways, e.g.M1 Macs can’t boot from an older release of Big Sur without setting that bootable volume group to Reduced Security using Startup Security Utility in recoveryOS.

This currently appears insoluble, making it essential to create each bootable system when that version of Big Sur is still current.

Full installers for older versions of Big Sur don’t work when run in a later release.

M1 Macs pose several problems for doing this: This article explores how successful making full clones can be, specifically whether you can use them to assemble a multi-boot disk containing multiple versions of Big Sur.ĭevelopers, researchers and system administrators often keep a collection of previous bootable systems so they can go back and run tests under those older versions, for instance when someone reports a bug which can’t be reproduced in the current macOS. The latest version 6 of Carbon Copy Cloner can now use macOS tools to make a full clone of a Big Sur System Volume Group, although this is no longer recommended. Until recently, the only reliable way to create an external bootable disk on an M1 Mac has been to install Big Sur on it, either in recoveryOS or using the full Installer app.

Osx carbon copy