Can I create a partition and store files I want to keep there, then do a fresh install to upgrade to Big Sur, or will the fresh install delete all partitions?

  • 2
    Your sure can, and depending on what you do and how you do the upgrade you could lose all your files. Your best bet? Back up your user profile to external media and then restore from that external media once done. Or at the very least make a backup, just in case something goes wrong, so you don't lose your files forever – Steve Chambers Feb 5 at 14:57
  • What version of macOS are you currently using? Could you include the output from the command diskutil list? This would give a better idea of your current partitioning. You may not need a new partition. If you are using APFS, then you could just create a new APFS volume instead. – David Anderson Feb 5 at 15:59

While upgrade procedures are tested before macOS is publicly available there always remains a slight risk that things go wrong and data gets lost. To be on the safe side, always make a backup on an at least one external device (two devices are even better) before upgrading macOS.


Installs can be side by side, but your files and folders and user data don’t merge if you have two or more systems. Some people store their user folders on one “volume” or “partition” and then have several systems share that account.

It all really depends what your goals are for the data and the apps and the OS versions. You have a ton of flexibility now with APFS and shared space storage management.

One new “trick” that’s very easy is install the new OS on a new volume and then migrate the data from the old “volume” - you do end up with two copies but if the new system breaks, you can delete it and go back to the old easily.

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