Walt Stoneburner's Ramblings

Currating Chaos

Drive Formatting Failure on macOS High Sierra

Attempting to format a new Seagate Expansion 4TB USB3.0 drive under Apple's macOS (Sierra or High Sierra) fails when the new drive is pre-formatted as NTFS for your PC.

Failed macOS Disk Utility Format of a New Segate Drive

Here is what the drive looks like when you look at it from the command line:

$ diskutil list

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/dev/disk5 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *4.0 TB     disk5
   1:         Microsoft Reserved                         134.2 MB   disk5s1
   2:       Microsoft Basic Data Seagate Expansion Drive 4.0 TB     disk5s2

IMPORTANT NOTE: In these examples we're showing the disk at /dev/disk5, your drive may vary -- and this is not something you want to get wrong.

If you look at the GUID Partition Table (GPT), it's full of stuff.

$ sudo gpt show -l /dev/disk5

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     start        size  index  contents
         0           1         PMBR
         1           1         Pri GPT header
         2          32         Pri GPT table
        34      262144      1  GPT part - "Microsoft reserved partition"
    262178        2014         
    264192  7813771264      2  GPT part - "Basic data partition"
7814035456        1678         
7814037134          32         Sec GPT table
7814037166           1         Sec GPT header
You want to destroy that before you use Disk Utility:

$ sudo gpt destroy /dev/disk5 # YOUR DRIVE MAY BE DIFFERENT

If you look at the GPT immediately after destroying it, it will look like this:

$ sudo gpt show -l /dev/disk5

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start        size  index  contents
    0  7814037167

At this point you can use Disk Utility or any other tool of your choosing to format it.

Finally, if the disk just won't eject, do this:

$ diskutil eject /dev/disk5