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I copy a 300 GB partition using GParted, and paste it onto an existing 500 GB partition. After two hours of transfer it says it's attempting to resize the newly pasted partition, and immediately fails to do so (editing the partition table to represent the correct size is a difficult operation, is it?).

This result makes no sense to me. Why would it ever need to resize the pasted partition at all?

The copied partition is either...

  • A. ...pasted in free space of sufficient size, or...
  • B. ...pasted over an existing partition of sufficient size. The existing partition of course has to be removed, making this case equal to A from that point.

I dont see any other feasible options. Either way we'd simply have to create a partition of the exact size we need before the transfer. So, why would I ever end up with a partition larger than the original in a copy operation? Nevertheless, Gparted just "copied" (distorted?) a 300 GB partition into a 500 GB partition.

To me this is not really a copy, and macOS does not recognize the new partition as containing an APFS container, so it's not usable.

Did I miss something here? What am I supposed to do before starting the 2 hour operation in order to know I'll end up with a usable copy (of the exact same size, of course)? Expecting GParted to do what appears most reasonable to me didn't work, and it's clearly not a task that lends itself to trial and error.

Or can I salvage the transferred data? I don't really know where the source was placed within the target partition.

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  • Perhaps you need to change the destination partition ID to indicate it is APFS Commented Sep 4, 2023 at 6:26
  • @JaromandaX I was planning on checking that today, but since everything is going wrong right now I was preparing to have to copy it all over again 🙂 You're right, it didn't copy the partition type. After fixing that macOS doesn't seem to mind the oversized partition.
    – Andreas
    Commented Sep 4, 2023 at 19:14

1 Answer 1

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While I still don't agree that ending up with a partition of the wrong size and type is a copy, the fixes weren't too complicated:

  1. Change the partition type to Apple APFS using gdisk
  2. Change the partition size in the GPT back to what it was originally, using fdisk. This works for APFS partitions since GParted couldn't possibly have resized the actual file system to span the whole partition (no stable APFS write support as far as I know).

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