Enter a password to unlock the disk macintosh hd - data

Hi Sebastian1237,

It appears that you improperly erased your Mac. Let me explain:

macOS Catalina and macOS Big Sur (you're running Big Sur) use two volumes to store data: the System volume (Macintosh HD, contains macOS), and the Data volume (Macintosh HD - Data, contains your apps and data). These two volumes are linked together in a volume group.

When you erase your Mac, both volumes will appear in Disk Utility. However, if you only erase one volume, the other one remains untouched and becomes unlinked from the volume that you just erased. I'm guessing that you erased "Macintosh HD", but left "Macintosh HD - Data" alone, which contained the previous owner's data. When you ran the macOS installer on the freshly erased "Macintosh HD", it linked that volume with a new data volume and installed macOS. The old data volume was left behind, and that's why you're now seeing the prompt to unlock the old data volume.

If you want to erase your Mac in Disk Utility, the correct procedure is to select either "Macintosh HD" or "Macintosh HD - Data", click Erase, then select Erase Volume Group. This erases and deletes the linked data volume, and then erases the system volume so that you can reinstall macOS.

Alternatively, to ensure that all macOS volumes get erased, you could select View -> Show All Devices in Disk Utility, and then erase the APFS Container. Doing that automatically deletes all volumes in the container, then makes a fresh new one.

But anyways, on to the solution for your issue. You'll need to identify the old data volume in Disk Utility and delete it. Follow the below steps to do this:

1. In macOS, open Disk Utility. It's located in Applications -> Utilities.
2. You'll see two entries named "Macintosh HD - Data". Select one of them, then check the Mount Point:
   1. If you selected the real legitimate Data volume, the Mount Point will be "/System/Volumes/Data". Also, the (-) button above "Volume" will be greyed out for safety.
   2. If you selected the old data volume, the Mount Point will be different than above. The (-) button above "Volume" will NOT be greyed out.
3. Select the old data volume and click the (-) button above "Volume". Click Delete to confirm.
4. Once that's done, the old owner's data will be deleted, and you should no longer see the password prompt.

Also, to answer your question at the end: No, the old owner's data will not transfer. That only happens if you explicitly approve it in Setup Assistant or Migration Assistant.

Hope this helps!

Hello Sebastian1237,

Thank you for using Apple Support Communities. It's our understanding that you're prompted to enter the encrypted disk password set up by the previous owner of your MacBook Air. You've come to the right place for help.

In order to remove all of the previous owners content, please follow all steps here: What to do before you sell, give away, or trade in your Mac

Let us know if this helps. Please include additional error messages and any other troubleshooting steps that you may have tried.

Have a wonderful day!

Erasing at the physical internal drive level works fine (and is pretty much failsafe) on Intel-based Macs, but it won't work on Macs with Apple Silicon. This is because Apple Silicon Macs use the following partition structure, which is different than Intel-based Macs:

disk0s1: APPLE_APFS_iSC (contains iBoot, LocalPolicy, and other critical firmware)

disk0s2: APPLE_APFS (contains macOS and user data)

disk0s3: APPLE_APFS_Recovery (contains recoveryOS)

Because there is no Internet Recovery on Apple Silicon Macs, and the necessary firmware resides directly on disk, erasing the entire drive renders the Mac completely unbootable (until it gets restored in DFU mode). Erasing the APFS Container at disk0s2, however, does not affect the firmware or recoveryOS, and is perfectly safe to do.

AFAIK, the only way to truly achieve a physical internal drive erase on a Mac with Apple Silicon is to restore it in DFU mode (that process recreates all three containers described above and activates the Mac). The second-best option would to complete the steps below. They work in macOS Catalina and later, which includes all Apple Silicon Macs.

1. Start up in recoveryOS. (Hold down Power button to get into Startup Options, choose Options and continue)
2. If you're asked for an admin password, skip to step 5.
3. Go to the top of the screen and select Utilities -> Terminal.
4. Type "resetpassword" (without the quotes) and hit Enter (Return).
5. A new window should appear. Go to the top of the screen and select Recovery Assistant -> Erase Mac.
6. Follow the onscreen instructions to safely erase the Mac. (This preserves the firmware and recoveryOS on Apple Silicon Macs; on Intel-based Macs, it erases everything.)

I would follow @Encryptor5000's "alternate" method so that the physical drive appears on the left pane of Disk Utility and selecting the physical drive to erase so that a new fresh partition table is created, before installing macOS again. Just make sure you have your data backed up first.