I bought a preformatted (NTFS) external drive and I want to re-format it with APFS using High Sierra (last upgrade). It is impossible. Whatever is the file system chosen, I always gat an error. What can I do? this is the second HD I bought. Different manufacturer, different capacity, but same problem. Thanks. Federico

  • Yes. If I do that Utility disk is unable to see the HD. even try to remove everything using a widows machine (that is perfectly able to reformat the disk using exFat or NTFS) but when I'm back to mac I'm always getting some error. Nov 9, 2017 at 13:56
  • Try zero-ing out the whole disk: In Terminal issue the command sudo dd if=/dev/zero of=dev/rdiskX where X is the identifier of the disk in question. You may need to issue the command diskutil list to determine it if you don't know what it is. After that, try again.
    – Allan
    Nov 9, 2017 at 14:06


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