Like many people online, I've been having issues with resizing my APFS Partition ever since Big Sur (11.1 BETA). There was a point in time where I had 500GB of unusable free space that I couldn't allocate to my functional partition of Big Sur!

Not too long ago I installed the Mac OS Big Sur Developer Beta on my computer. It was alright – a few issues here and there, but nonetheless not bad for a beta. After Big Sur was officially released, I wanted to get out of the Beta and remain on the public version of Big Sur. Of course, that's no easy task. So what I decided to do was partition my drive (500 GB / 500 GB), install the public version of Big Sur on the new partition, and then move all my files over – It worked! Now it was time to resize the new partition after formatting the old one so that my new partition was the full 1 TB of available space – and that is where this tutorial will help. For some reason, with Big Sur, I was unable to change the size of the Partition. I tried every single command-line google had to offer – I even went as far as using Recovery to run GPT commands. The furthest I got from that was the ability to recover the "Free Space" and use the 1st partition as a drive, but it was still considered separate from my main Big Sur partition.

What do I do to retain my entire storage in 1 partition?

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    Commented Dec 17, 2020 at 23:13
  • That was my original plan! To remove and expand the containers. In fact, I tried that many times before this solution. It just wouldn't work! diskutil was having trouble removing and expanding containers due to an issue with Big Sur Commented Dec 18, 2020 at 4:50

1 Answer 1


Found a Solution!

What you'll need:

  1. A Second Mac (With enough storage to backup your files)
  2. A Bootable USB Big Sur Drive (Apple has great docs on how to make that)
  3. A Thunderbolt cable (and respective adapters to establish a connection between the first (Problem Mac) and second Mac)
  4. Time

Before you start just know that you will lose your preferences and installed Apps (Some apps may be transferred by the methods below). If you use Time Machine, you might be able to hold onto your preferences and Apps.

You may be able to use a time machine backup, but I haven't tested it. If you want to use a time machine backup, Mount your Troubled Mac (covered in Step 1) and then skip to Step 2.

Step 1

From the Troubled Mac: Turn off your issued Mac, then turn it on and immediately hold down 'T' on your keyboard. Plug in your thunderbolt cable.

From the Second Mac: Plug in the other end of the thunderbolt cable, go to disk utility, find the Hardrive(s)/partitions of your troubled Mac, Right-click on all partitions and choose "Mount" – You may be asked to enter the password for the drives. Right click on the "-Data" drive and choose "Show in Finder". Navigate to your home directory where you'll find all your files.

Continuing on the Second Mac: Make a new folder in a safe spot. Move over all your files from the issued Mac ("Show in Finder" Finder Window). Patiently wait until you have secured a copy of all your files on the Second Mac.

Step 2

This step may be able to be completed from Recovery/Bootable Installer command-line. Not Tested

From the Second Mac: Open up terminal and type in

diskutil list

You'll get a list of all the drives, including the attached Target Disk (Troubled Mac). Note the disk identifier of the troubled Mac (In my case it was disk3; yours may be different). With your Partitions still mounted through Disk Utility, type in the following command:

diskutil partitionDisk disk3 1 GPT HFS+ Untitled 100%

This will format the troubled mac's SSD/HDD to an HFS+ partition. Note: If you receive the "Can't open" error, double check that the troubled Mac is A) Mounted in Disk Utility and B) Not being used by another application such as a Recovery Program or Transferring Files!

Once completed, you'll see the new "Untitled" drive in Disk Utility, formatted as an HFS drive. Select the new "Untitled" drive in disk utility and click "Erase" along the top menu. Choose to erase as "APFS" (Don't choose encrypted) and Give it a nice title – How about "Macintosh HD". Click "Erase". You've fixed your hard drive Allocation/Partition Problem!

Step 3

From the Troubled Mac: Hold down the power button for 10 seconds to shut off the computer. Plug in the Bootable Installer USB. Turn on the Mac and hold down the "Option" key until you see the Bootable Drive. Select it. Install Mac OS Big Sur Public as normal. Set it up and Log yourself in. Wallah! A fresh Mac that is the full hard disk size!

Step 4

If you are using a time machine backup, restore from Time Machine and you should be good to go!

There is a good video by 9to5mac on how to do this step if you are not using a time machine backup

With your newly formatted Mac still plugged into the Second Mac, go to System Preferences on Both Macs.

On Both Macs: go to network settings and click "+". Add a thunderbolt bridge connection. Note the IP address from the Second Mac.

On The Second Mac: Go back to Sharing Preferences. Check mark "File Sharing".

On The Newly Formatted Mac: Go to Finder. Hit "Go" in the top menu bar, then select "Connect to Server". Enter the IP address you noted from the Second Mac and hit "Connect". After a few moments you'll be asked to login, in which you'll enter the credentials for the Second Mac. The Second Mac should now be mounted as drive on the Newly Formatted Mac where you can move your files back over to their respective folders.

Finished! If you've made it this far, I know you were as desperate as I was. I hope this was able to help a few of you – And for those of you that knew this, WHERE WERE YOU WHEN I NEEDED YOU?! Let me know if this worked out for you. Happy Big Sur-ing.

  • The man pages for the diskutil command recommend using the diskutil partitionDisk disk3 1 GPT HFS+ Untitled R command instead of the diskutil partitionDisk disk3 1 GPT HFS+ Untitled 100% command used in your post. Commented Dec 18, 2020 at 9:56
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    Actually, you do not need another Mac. You can use the asr command to clone, then use the diskutil command to remove and expand APFS containers. For example, see the accepted answer to the question How to make remove free space and make APFS container take it up. However, sometimes a clean install using your answer would be the better way to go. Commented Dec 18, 2020 at 11:29
  • Adding links to the websites you refer to would be helpful. For example, you refer to Apple and 9to5mac. Commented Dec 18, 2020 at 11:36

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