A GUID Partition Table (GPT) partitioning scheme is required

Question

A GUID Partition Table (GPT) partitioning scheme is required

I might have figured out why this isn't working, but I don't much like the answer if I'm right.

I've been trying (unsuccessfully) to encrypt an external USB drive, and so far every single piece of documentation I can find all say the same 2 things. Either:

In Finder ctrl+click the device in the sidebar and select "Encrypt" from the context menu, or
Format the with Disk Utility using the APFS option with encryption (I may not have that exactly right but it doesn't matter as you'll soon understand).

Neither of these procedures is even possible, because those options are not available. Finder offers no such option in the context menu:

"But," I said (actually out loud), "perhaps option 2 is required before we have option 1 available since the disk was formatted as Ex-FAT." So off to disk utility we go.

After copying the one folder I wanted to keep to my system drive, I set about nuking the whole thing from orbit (it's the only way to be sure). To my dismay, APFS was not an available option for formatting, so I opted for Mac OS Extended (Journaled), and since I was doing this, may as well scrub the thing right, so I added the 7-pass wipe to the mix just to be sure nothing would still be hanging around later gumming things up and disconcerting the passers-by. And then I left it running and went to bed, because 2 hours later, we had just finished the first pass.

Morning came, and with it a freshly formatted 128 GB of pristine digital landscape all ready to be encrypted and...

I still didn't have the option to encrypt.

Back to disk Utility where Aha! I see "Convert to APFS" in the context menu now. (The game's afoot!)

Not so much.

Searching for this specific error yields the same advice I got with a less specific search -- and all of the answers that make people go "Thanks! That did it! Huzzah!" were one or both of the same two I already mentioned. Which (as I also already mentioned) are apparently not an option, but I don't know why.

I was speculating (though it really didn't make sense) that perhaps having the M1 chip might be a factor, because almost all of the community posts I found on the subject that mentioned hardware at all all reference one of there Intel chips. But my partner's Mac exhibits the same behavior, and hers is an i5 so that's not it. (Cue sad trombone.)

What they do have in common is Monterey. Which the community hasn't mentioned in any of the threads I've read. The latest I remember seeing was Catalina, but I can't say that there wasn't a Big Sur in there somewhere.

But at the end of the day, root cause analysis is fascinating, but all I really want to do is encrypt this drive. So if anybody has any ideas that aren't covered by the ones I've already heard, I would welcome them.

MacBook Pro 13″, macOS 12.2

Posted on Feb 13, 2022 9:28 AM

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Answer 1

Top-ranking reply

James Brickley

Level 5

5,062 points

Feb 13, 2022 1:09 PM in response to wendysboyfriendjames

In the GUI Disk Utility click the View menu and click Show All Devices. Then make sure you click on the Disk itself and not the volumes nor containers within. You then set the scheme to set GPT. You can choose APFS (Encrypted) and set a password. If you eject / unmount it and re-mount it you will be prompted for the password and there's a checkbox to save it to the keychain. There is little need for Case Sensitive with APFS unless you have a specific edge case that requires it.

Don't forget that password there is no way to reset it.

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Answer 2

dialabrain

Level 10

124,751 points

Feb 13, 2022 11:10 AM in response to wendysboyfriendjames

FWIW, you need to change "View" to "Show All Devices" in Disk Utility. Then select the top level of the drive to format.

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Answer 3

Barney-15E

Level 10

116,302 points

Feb 13, 2022 11:10 AM in response to wendysboyfriendjames

The option isn't available in the default view in Disk Utility.

You have the change the View to "Show All Devices," then format the actual device (drive), not the formatted volume.

A drive has a partition table. That partition table divides the drive into Volumes.

macOS can only encrypt a device with a GUID partition table. An ExFAT drive most likely has an MBR partition table. You have to format the drive, not the partition.

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Answer 4

Feb 13, 2022 12:57 PM in response to MartinR

I did indeed attempt to use Disk Utility, but it wasn't offering the option to set a partitioning scheme at the time. Or if it did, I missed that step -- I can't rule it out, but you'd expect that to be something the app would ask for right up front. I can say that once I nuked it in Terminal and started over, it gave me that option right off.

It did, quite effectively, erase the disk, and get it from Ex-FAT to jhfs+, and it wasn't bootable, and since we already know it wasn't GPT, I htink the remaining possibility is APM(?).

Anyway, after poring over the very page you linked to, and drilling down another link I was able to thrash around in Terminal enough to partition the disk (after a fashion) with diskutil, which didn't actually solve the problem, but it gave Disk Utility enough to start with that it could create a volume and a mount point, and I was able to specify the APFS Case-sensitive, Encrypted option for the file system and create a password for it. So far, I haven't had to supply said password to open anything, but I'm still admin (and the owner) so maybe it just knows. Finder does show the option to Decrypt it now, so I'm going on the assumption that it worked.

I suspect this had more to do with how the drive was configured out of the box than anything.

I'm not sure how I'd document this resolution in an incident if it happened at work, because "thrash around in diskutil until something gives" isn't exactly a "repeatable process", but what appeared to get it "unstuck" was:

diskutil partitionDisk disk4 GPT %APSFX% foo 0

That didn't solve the problem entirely, because it didn't create a volume or a mount point, but it got the jam cleared so I could do all that in Disk Utility.

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Answer 5

MartinR

Level 7

21,595 points

Feb 13, 2022 10:45 AM in response to wendysboyfriendjames

Have you tried using Disk Utility to erase the USB drive and set the partition scheme to GUID Partition Map? At that point you can also select an encrypted file system format from the Format pop-up menu.

The error message you got was that DIDIVO128 (your USB drive) needed to have a GUID Partition Map before it could be converted to APFS. I suspect your USB drive is currently MBR (master boot record) partition scheme.

For more information, see File system formats available in Disk Utility on Mac

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Answer 6

Feb 13, 2022 10:57 AM in response to Old Toad

Recapping (briefly this time)...

TL;DR: I've done both of these (to death) already:

In Finder ctrl+click the device in the sidebar and select "Encrypt" from the context menu, or
Format the with Disk Utility using the APFS option with encryption

Neither option has worked so far, because neither option is available.

So the infinite loop I find myself in is:

The option to encrypt is not available because the drive is not formatted as APFS
Because the disk utility doesn't offer APFS as an option when formatting the drive

(Is anyone else seeing the "I clearly can't drink the wine in front of me" scene from The Princess Bride after reading that? No? Okay, just me then.)

I guess I should've included this screen shot too.

(These are still the only available options, so formatting it as Mac OS Extended didn't get me any closer than I already was.)

Right clicking on the desktop icon isn't functionally different from right clicking in Finder but I tried it anyway because it only takes a second to be sure...

Yep. That's what I figured.

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Answer 7

Feb 13, 2022 11:03 AM in response to wendysboyfriendjames

For starters what you have is a USB-C / USB-A Flash Thumb Drive. I would definitely avoid secure wiping with multi-pass on such a device as it will shorten the lifespan and it won't actually wipe anything. The multi-pass option is for older HDDs that are magnetized disk platters. The secure multi-pass wipe is to ensure data is completely unrecoverable and is necessary due to the magnetic properties of the storage medium. Simply formatting or erasing can leave residual data that can be recovered. This is not the case with flash memory. If flash memory is erased, the data is gone and irrecoverable.

I don't have a DIDIVO128 drive to test but I do have a Patriot Memory flash drive and that seems to work. I do have a SanDisk USB-C / USB-A flash drive and I also tested that one as well. Not going to bother with the screenshots as they are all the same.

It is possible that the DIDIVO128 is doing something weird or they have their own software to encrypt.

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Answer 8

Feb 13, 2022 1:10 PM in response to James Brickley

I suspect that the good folks below may have hit on why I was having so much trouble. The default view is "Show only volumes" which if I'd noticed that, might have saved me a lot of time (and typing). Now that it's been beaten into submission, when I open that view I can almost trace the steps I took. I've seen weird little autorun utilities and encryption programs come preinstalled on other brands of thumb drives before, but this one didn't have any. I got it because it had both USB -A and USB-C connectors, which made it easy to go from my old machine (which only has the old USB-A) to my 2020 MBP (which only has 2 USB-C ports).

I got there (more or less) it just took way more work than I wanted to do on a Sunday afternoon.

Thanks for the tip on wiping flash drives. I may have known that at one time, but it's not something I have to think about very often.

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Answer 9

Feb 13, 2022 1:17 PM in response to James Brickley

Thanks for that. And all the details earlier too. I eventually got there, just in a very "educational" way that would have been a lot less of a teachable moment if I'd noticed the View menu to begin with.

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Answer 10

Feb 13, 2022 1:25 PM in response to Barney-15E

Yeah, that would have saved a lot of effort and irritation if I'd seen it. And you're correct about the partitioning scheme, I have a second (larger) drive of the same brand that didn't need encryption, so it was still in the configuration it was shipped with. Plugging that in, and looking at the top level info for it, it is indeed MBR.

But I learned some stuff, so win.

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