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Can't encrypt external hard disk using High Sierra

Hi. I'm using High Sierra, and I've just bought a new external hard disk drive for additional storage. I've plugged it in and erased it using Disk Utility as Mac OS Extended (Journaled). But it didn't offer an encryption option, so I can't password protect it. I've plugged in other drives which ARE password protected, and these DO give the encryption option. Can anyone help?

MacBook Pro (Retina, 15-inch, Mid 2015), macOS High Sierra (10.13), null

Posted on Oct 20, 2017 11:11 AM

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Posted on Dec 4, 2017 10:05 AM

I had the same problem (no encryption options, partition button greyed out) and also solved it. In my case, the problem was that my new drive (La Cie Rugged Thunderbolt from the Apple Store) came with a master boot record partition map and not GUID. If a drive is not GUID, neither the partition button nor the encryption settings are available in the graphical Disk Utility, which is why we're forced to use the command-line diskutil to partition first.


In the Terminal app, I used:

diskutil list


to find out that my new drive was mapped to /dev/disk2. Then I used the following:

diskutil partitionDisk /dev/disk2 GPT JHFS+ YourPartitionName 0b


...to partition the disk using a GUID partition map (GPT is the argument that specifies GUID) and Journaled HFS+.


This ran successfully and the encryption and partition options became available in Disk Utility.


This post has a good overview of how the command's arguments work so you can be sure of what you're getting:

http://www.theinstructional.com/guides/disk-management-from-the-command-line-par t-2


Hope this helps others not waste as much time as I did trying to make this work.

14 replies
Question marked as Best reply

Dec 4, 2017 10:05 AM in response to Tator75

I had the same problem (no encryption options, partition button greyed out) and also solved it. In my case, the problem was that my new drive (La Cie Rugged Thunderbolt from the Apple Store) came with a master boot record partition map and not GUID. If a drive is not GUID, neither the partition button nor the encryption settings are available in the graphical Disk Utility, which is why we're forced to use the command-line diskutil to partition first.


In the Terminal app, I used:

diskutil list


to find out that my new drive was mapped to /dev/disk2. Then I used the following:

diskutil partitionDisk /dev/disk2 GPT JHFS+ YourPartitionName 0b


...to partition the disk using a GUID partition map (GPT is the argument that specifies GUID) and Journaled HFS+.


This ran successfully and the encryption and partition options became available in Disk Utility.


This post has a good overview of how the command's arguments work so you can be sure of what you're getting:

http://www.theinstructional.com/guides/disk-management-from-the-command-line-par t-2


Hope this helps others not waste as much time as I did trying to make this work.

Jan 2, 2018 10:41 PM in response to Tator75

Non-Terminal Solution: (to make the drive GUID)


1. Disk Utility > "View" (Top Left Corner) > "Show all Devices"


You will now see the full drive (not just the partition) on the left side.


2. Right click the drive in question (top drive, not the sub partition) > "Erase ..." :


"Name: Untitled"

"Scheme: GUID Partition Map"

"Format: .... Encrypted options will now be available.


3. You will be prompted to enter a password.

Dec 1, 2017 10:10 AM in response to Tator75

Just to be clear, and to give foolproof instructions, is this what should be entered in Terminal? (The name of the external hard drive I am trying to do this with is named “Silver HDD”):


diskutil partitionDisk /dev/silver hdd 1 GPT HFS+ newdisk R


After using the above, do I then need to enter this into Terminal?


diskutil eraseDisk HFS+ newdisk /dev/silver hdd


Anything else?


Per: terminal - How do I force a partition and format on a USB key in OS X Mountain Lion Disk Utility or from CLI diskutil? -…

Dec 1, 2017 11:39 AM in response to whyyouareeye

Ok, that didn’t work. Here is what did and finally got Disk Utility to give me the encryption option using this command in Terminal first:


“diskutil list” to get a list of the mounted disks (I only had my one internal drive, which is in just one partition). Thus, the external drive I wanted to reformat/erase was the third in the list and indicated by “disk 2”.


Then, I used this command where I “Silver” was the name I wanted to name the new formatted disk:


“diskutil eraseDisk JHFS+ Silver disk2"


After doing all that, I then used the regular Disk Utility application to “Erase” the disk and selected the encrypted option.


Hope this helps!


(I found part of my solution from this site: https://www.maketecheasier.com/format-external-drive-osx/)

Can't encrypt external hard disk using High Sierra

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