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I have recently found that FileVault is disabled on my machine. Although I remember that I set "encrypt" option when I was setting the machine up.

I opened System Preferences and enabled FileVault. To my surprise it didn't take any time. I didn't have to wait while the data is encrypted. It just got instantly enabled.

My configuration: MacBook Air 2018, 256Gb SSD, macOS Mojave 10.14.1

I understood that the disk is not encrypted because I was able to access the content from my home directory from a guest session.

How does it possible that turning on FileVault doesn't take any time?

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    There are 3 main implementations of FV. Can you specify what machine you have (model year ideally) and what version of macOS? We'll need to know if you have an SSD or HDD. We might even need to know if you have diskutil cs list or diskutil apfs list to know if the conversion is still happening in the background. – bmike Jan 19 at 13:40
  • Excellent edit! That’s a great Mac. I will edit my answer to make it very specific to your situation. I really appreciate the test you made - super good to check on and understand when encryption won’t help you and when it will. – bmike Jan 19 at 22:05
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You have a new Mac with an SSD and T2 chip so all data on it is encrypted always. Any election you make in FileVault just adds and removes user keys from the trust chain so that happens basically instantly. However, when a FileVault credentialed user isn’t created, the system unlocks itself so the encryption door is always wide open.

The next time you restart, the system will notice that the first per-user key is now active and change the boot process so that the system won't unlock that storage and start the OS until your key unlocks the storage. Keep in mind, FileVault by default on APFS is all or nothing. When you unlock the storage, any account can read any files it has permission and you need your password to keep other users (guests) off your files and session.

You can inspect this by looking at diskutil apfs list to examine each APFS containers and synthesized volume encryption and lock status.

mac:~ me$ diskutil list
/dev/disk0 (internal):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                         251.0 GB   disk0
   1:                        EFI EFI                     314.6 MB   disk0s1
   2:                 Apple_APFS Container disk1         250.0 GB   disk0s2

/dev/disk1 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +250.0 GB   disk1
                                 Physical Store disk0s2
   1:                APFS Volume Mac                     191.7 GB   disk1s1
   2:                APFS Volume Preboot                 65.4 MB    disk1s2
   3:                APFS Volume Recovery                1.0 GB     disk1s3
   4:                APFS Volume VM                      3.2 GB     disk1s4

Be sure to restart your machine and test the guest session scenario again. Only a full “Guest account” that’s set up in user preferences will keep your data marginally protected when you have an unlocked / unencrypted synthesized Macintosh HD boot / OS / user volume.

  • Thank you for the answer. My laptop does have T2 chip (please find an update in the description). By marking "encrypt" checkbox during system setup I thought it would already turn on FileVault and protect my system. If that is not the case I doubt such protection worth anything (as I said I was able to access my home directory content from a guest session which is a frightening fact). Am I missing something? – Oleksandr Shpota Jan 19 at 20:42
  • @OleksandrShpota That is by design. Filevault (in its current implementation, Lion and later) and Windows Bitlocker are called "full disk encrpytion". They lock the entire disk as a single entity. Once they are unlocked, FDE allows the OS to read the entire disk. It is the responsibility of the OS to enforce permissions on individual users. – user71659 Jan 19 at 21:12
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I didn't set "encryption" on while installing my System, but turning on Encryption with FileVault afterwards definitely takes time (about 45 min with a 512 Go SSD).

Decrypting the disk will take time with a background process as well.

You can check if your disk is encrypted or not (or in progress) through the Terminal with entering this command:

sudo fdesetup status

From your experience, it looks like enabling encryption during setup does the work, but doesn't show up in the "System Preferences" until you explicitly turn it on?

enter image description here

  • Excellent answer covering the non APFS and non-T2 situation. This dialog will show for APFS (lacking T2) and all CoreStorage FileVault situations other than the original FV that made a sparse disk image instead of encrypting the whole volume. – bmike Jan 19 at 13:49
  • I'm just guessing - you could still be right for this case. We don't have enough data from OP yet to tell. I do know this answer will help other people +1 for that – bmike Jan 19 at 13:59
  • Thank you for the answer. Please find an update in the description. – Oleksandr Shpota Jan 19 at 20:44

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