Let me tell the story from the beginning: I installed Big Sur on an unsupported Mac using guidelines at Medium. In the guide it was stated that I should create a separate partition for Big Sur, and shouldn't install it on my current one. I had my SSD Called "Macintosh SSD" and later I created a partition named "Macintosh SSD Big Sur" of size 40GBs. After installation I wanted to clear the "Macintosh SSD" of size 80GBs(with old MacOS) and merge it with the new "Macintosh SSD Big Sur".

This is what I initially had after formatting partition with the old MacOS enter image description here

So, I used the command sudo diskutil apfs deleteContainer disk3 after which I had (free space) in /dev/disk1

enter image description here

I want to extend that 39.6GB partition which free space of 80,1GB but all the commands I googled do not work:(( Could you please guide me on what I should do now? Thank you in advance!


2 Answers 2


Your free space is before your disk2. The start position of a partition is fixed, and you can only resize the partition by changing the end position. You should back up your data, erase the disk as one partition and restore from backup.

  • Thanks for the prompt answer! Is there anything I can do with gpt create command?
    – Victor
    Sep 2, 2020 at 13:32

Since the relevant space used on disk1s3 is sufficiently smaller than disk1s2, you can clone Macintosh SDD Big Sur from disk1s3 to disk1s2. After this is done, you can remove disk1s3 and expand disk1s2 to contain the space occupied by disk1s3.

Cloning can be accomplished by using the Disk Utility to restore to the container occupied by disk1s2. When restoring, choose to restore from Macintosh SDD Big Sur. The proper files will also be cloned from the Data, Preboot and Recovery volumes. You will need to run the Disk Utility from macOS Recovery. A Big Sur version of macOS Recovery may be required. In other words, restart the Mac and immediately hold down the Command and R keys.

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