Disk Utility fails to encrypt folder with 'Operation not permitted' error on Mac mini

Where are you seeing the option to encrypt a folder in Disk Utility? I can't find any menu that alludes to encrypting a folder.

Are you referring to creating an encrypted disk image?

P.S. I'm also on a Mac Mini M4 running Sequoia 15.6.1.

Eric in Oakland wrote:

Yes, and I figured out the problem.

I was trying to encrypt a folder on an external drive. Once I copied it to the desktop it worked fine.

Thanks for your reply!

Just curious about the file system on the external drive you were using here.

I have seen issues with creating DMGs & sparsebundles on external drives with a non-Apple file system. I would not expect any issues if using HFS+ or APFS.

Eric in Oakland wrote:

Yes, and I figured out the problem.

I was trying to encrypt a folder on an external drive. Once I copied it to the desktop it worked fine.

Thanks for your reply!

I wonder if it’s a full disc access problem. I would think disk utility itself would have full disk access in order to format an external drive, but the disk image utility may not have full disk access.

Again, where is the option/menu to encrypt a folder located. I couldn't find it.

Old Toad wrote:

Again, where is the option/menu to encrypt a folder located. I couldn't find it.

It is under the "Convert...." menu option (I was curious too).