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Unlock FileVault disk after failed Big Sur installation

G

Goldex

macrumors member
Original poster
May 15, 2009
54
86
Quick summary: I tried to install Big Sur on a Macbook Pro (Retina, 13-inch, Mid 2014) but this failed and now I can't access it anymore. Now I'm trying to access it through Recovery Mode to back up some files, but the FileVault password claims to be incorrect. Any ideas?

Midway through the macOS Big Sur installation, a message popped op saying "An error occurred preparing the software update", only giving me the option to restart. Now the device still starts up normally to the login screen, but when I sign in with the user, it ends up with black screen and a prohibitory symbol. Accessing the Mac in Safe Mode (Shift) or Single User Mode (CMD+S) both failed in the same fashion.

I presume the only way to do anything is through Recover Mode. Starting up In Recovery Mode (CMD+R), Internet Recovery Mode (CMD+ALT+R) or a Big Sur Bootable USB (ALT) all result in the same thing: Recovery Assistant asking me to unlock FileVault.

The default password to my account does not work; it claims to be incorrect, even though it's not (100% certainty, it only consists of a few numbers). Different keyboard language settings have no effect. I read this might have something to do with Administrator rights being disabled during installation, and I also read a SMC reset might do the trick. Unfortunately, no luck.

The other option is to sign in with an Apple ID. If I use the Apple ID assigned to the user of the Mac, when I hit "Unlock Account", no Two-Step Verification is send to another device; it just says "An unknown error occurred". When I use a completely different Apple ID, it does send a Two-Step Verification request, but when I approve and enter the 6-digit code, it says "The supplied iCloud account was unable to unlock this volume" (obviously).

Does anyone have any ideas on how to unlock FileVault and access the disk?
 
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Goldex said:
Recovery Assistant asking me to unlock FileVault.
Click to expand...
I would like to see a picture of this request. I suspect you're not providing what it's asking for.

But if you are, and it's not working, you've likely lost all access to that disk.
 
chabig said:
I would like to see a picture of this request. I suspect you're not providing what it's asking for.

But if you are, and it's not working, you've likely lost all access to that disk.
Click to expand...
I provided pictures here: [link] Both of the Startup Disk screen where I can unlock the volume without success, and the Recovery Assistance asking for the password of the account. This is currently the only options I have In Recovery Mode.

The password for the user still works when I boot up normally so I know its correct, however midway loading it shows the black screen with a prohibitory symbol.

And you're right, it doesn't specifically say FileVault, but the disk is encrypted and I need to unlock it, I presume this is due to FileVault.
 
Thanks for the picture. It does seem to be asking for a password of a user account. If you have more than one account, try them all. Check key caps! Do you have a FileVault recovery code saved somewhere- try that.

Otherwise I think you’re stuck. There is no workaround for FileVault encryption.
 
Did you create a password hint when you set up your Mac password? If so, have you seen the white ? mark symbol when It ask for your password?

Boot into Recovery mode (Spinning Globe)
When Mac utilities comes up, pick Terminal
In Terminal enter the following: resetpassword and press Enter
Open Reset Passord Manager and select 'my password doesn't work'
Click Next and follow the prompts

If that doesn't work, I think you are out of luck.
 
Last edited:
Is this YOUR MacBook?
Or... does it belong to somebody else?

My thoughts are that the data on it is gone, and will never be retrieved.

Time for a visit to the Apple Store genius bar, if there is one reasonably close that is open for business.
 
KaliYoni said:
This article might help you figure out what is happening:
mrmacintosh.com

Big Sur Upgrade not Enough Free Space = Serious Issue & Possible Data Loss! UPDATED

Did you try upgrading to macOS Big Sur & got An error occurred preparing the software update? I'll expain + recovery workaround inside!!
mrmacintosh.com mrmacintosh.com
Click to expand...
Thanks for the article link. I experienced this problem last weekend. I went through the proper process of erasing the disk and trying to reinstall BS 11.2 and kept experiencing "Big Sur Recovery startup disk screen that shows blank = no startup disk available." My disk wouldn't mount. It is good to know that it wasn't an error on my part but, good ole 11.2 that was the problem. I finally got 11.2 clean installed.

I had to figure it out on my own. Calling Apple support was useless. The kind lady kept referring me to the process I had tried several times already and then she wanted me to do a restore from Time Machine backup. I had to politely inform her that that was no longer possible with Big Sur.
 
How did you finally solve this as I have the same issue. It won't take profile password or icloud password. Even when successfully reset.
 
What you can try to do is target discount. You’re gonna have to have another Mac with Mojave later. I am connecting external drive to that other Mac. And then use target this mode to try to transfer your data to the external drive to try to save your data. Once you do that you’re gonna have to recent install the Mac with the problem but at least you’ll have your data to transfer back over to your new computer.
 
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