Unable to use free space shown by diskutil in macOS

Question

I have a 2TB external drive (disk2) that used to have a volume (disk2s4) and two APFS containers (disk2s3 and disk2s2). I removed one of those volumes (500GB disk2s2) thinking I could then resize the other (disk2s3), but now I can't use those free 500GB at all.

➜  ~ diskutil list disk2
/dev/disk2 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *2.0 TB     disk2
   1:                        EFI ⁨EFI⁩                     209.7 MB   disk2s1
                    (free space)                         500.4 GB   -
   2:                 Apple_APFS ⁨Container disk3⁩         500.0 GB   disk2s3
   3:                  Apple_HFS ⁨Storage⁩                 999.6 GB   disk2s4

Can't resize disk2s3

➜  ~ diskutil APFS resizeContainer /dev/disk2s3 0
Started APFS operation
Error: -69519: The target disk is too small for this operation, or a gap is required in your partition map which is missing or too small, which is often caused by an attempt to grow a partition beyond the beginning of another partition or beyond the end of partition map usable space

Nor create another partition (of any size and format)

➜  ~ diskutil addPartition disk2 ExFat FOO 0
The new partition to be added will be of a filesystem personality of ExFAT exfat ExFAT Windows_NTFS
The new partition will be added following disk2s4
Started partitioning on disk2
Error: -69519: The target disk is too small for this operation, or a gap is required in your partition map which is missing or too small, which is often caused by an attempt to grow a partition beyond the beginning of another partition or beyond the end of partition map usable space

How do I "move up" this disk2s3 so that the (free space) is at the "end" and I can use it again?

Answer 1

Apple's built-in tools only let you stretch or shrink a partition from the end; they never let you move the start of the partition.

You could manually do this as a multi-step process:

1. Make a new 500GB partition out of the free space.
2. Clone the existing 500GB partition onto the new partition.
3. Test the new clone to make sure everything copied fine.
4. Delete the old partition.
5. Stretch the new partition to take up the space you just freed up.