Filevault on External drives - can this work?

Discussion in 'macOS' started by Sean Dempsey, Dec 20, 2015.

  1. Sean Dempsey macrumors 68000

    Sean Dempsey

    Aug 7, 2006
    I have 3 external drives.

    Drive-A is a nightly "smart update" bootable copy of my OS by Chronosync
    Drive-B is external file storage
    Drive-C is a copy of B "smart updated" nightly by Chronosync

    I know I can Filevault these drives, but I have questions and Google is no help.

    Q1: If I Filevault these drives, what happens upon boot? Are they unmounted until I manually mount manually?
    Q2: If I need to boot to the OS external clone, will I be able to boot to it over USB 3?
    Q3: Will drive B be able to copy to drive C like normal if they are both mounted properly?

    I'd prefer the encryption of the externals to be transparent unless the drives are powered off, as I can't always be around to mount the drives if they become unmounted.

    What is the practice for encrypting backup drives?
  2. chabig macrumors 601

    Sep 6, 2002
    I keep several encrypted externals.

    A1. They'll auto mount if you tick the checkbox that stores the password in your keychain. This behavior is up to you.
    A2. I don't know, but you would at last have to enter the password.
    A3. Yes, the drives behave normally when mounted.
  3. Weaselboy, Dec 20, 2015
    Last edited: Dec 20, 2015

    Weaselboy Moderator


    Staff Member

    Jan 23, 2005
    Just to expand on what chabig said about #1. The first time you attach the drive and mount it you will get a popup asking for the password. At the bottom of that box is a checkmark to save the password in Keychain. If you enter the PW and check that box, you will never be asked for the PW again. When you attach the drive it will just mount on its own going forward.

    On #2... no it would not be bootable since it is encrypted. But what you can do is make a 1GB recovery key using this utility, then option key boot to the recovery key and from there use Disk Utility to mount and unlock the drive then restore the external to the internal also using Disk Utility. I'm assuming you are asking this in case you need to replace an internal drive.
  4. chabig macrumors 601

    Sep 6, 2002

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