I turned on/off the FileVault to reset my password and I still cannot access the Macintosh HD

arcielee wrote:

I have a MacBook Pro for my job and over 80 GBs of my hard drive is tied up with Other Volumes. I saw one solution advising to mount the Macintosh HD - Data, but it prompts me for a password.

This indicates that macOS was improperly installed/re-installed at some point and there is an extra "Data" volume most likely from the previous owner which is why you don't have the proper password to unlock it.

@Encryptor5000 is correct that performing a clean install of macOS is best. If you have an Intel Mac, then I suggest erasing the whole physical drive instead of deleting volumes or Containers. If you are booting to a macOS 10.13+ installer on an Intel Mac, then you will need to click "View" within Disk Utility and select "Show All Devices" so that the physical drive appears on the left pane of Disk Utility. The internal physical drive should be the top most item which should be identified by the make & model number of the drive such as "Apple SSD .....". If you have an M1 Mac, then follow @Encryptor5000's instructions to delete the volumes instead.

FYI, it is always best to perform a clean install of an OS by first erasing the drive whenever you acquire any pre-owned computer. You never know what nasty little surprises may be lurking on the drive from the previous owner and you don't know whether the OS is in good working condition. Plus performing a clean install of the OS may reveal hidden issues that otherwise may go unnoticed so that you won't be able to return the computer for your money back.

Here is what Apple suggests a person does when selling their Mac (my modifications to the drive erase section is better than Apple's instructions if you have an Intel Mac):

What to do before you sell, give away, or trade in your Mac - Apple Support

Hi arcielee,

If you received this MacBook Pro from a previous owner, it's likely that it wasn't properly erased.

A typical macOS install utilizes two volumes: Macintosh HD (the signed system volume), and Macintosh HD - Data (the Data volume). When you're using your Mac, these two volumes appear to be merged together and act like one.

When erasing a Mac in Disk Utility, the Data volume should be outright deleted, and the system volume should be erased. I think that this did not happen; instead, the system volume got erased alone and the old Data volume was preserved by accident.

To fix this problem and delete the old Data volume (which is protected by the previous user's password), complete these steps:

1. Open Disk Utility, located in Applications -> Utilities.
2. You should see two entries for Macintosh HD - Data. Select one of them.
3. If the Delete (-) button is available, click on it. If it is greyed out, select the other Data volume, then click the (-) button.
4. Click Delete to confirm.

Changing the FileVault setting for encrypted/not-encrypted state of a drive takes under a minute.

HOWEVER, the actual conversion takes All Afternoon, and makes progress only while your Mac is awake. In addition, you can not cancel the conversion, nor can you make a new request about the encrypted/decrypted state of the Volume until the previous conversion completes.

The process requires your Mac to read in blocks of files, switch their encrypted state, then write them out again. The whole Volume must be processed. The work is done at low priority in the background, so that you can continue to do your important work while the conversion is taking place.

That is correct and good to point out. However, OP mentioned that they received the Mac for their job and it already had the extra volumes on it (considering the password was not provided, it most strongly suggests a botched erase). With FileVault (APFS encryption), there's no way to reset a password unless the volume can be unlocked, and because the old Data volume was tied to previous credentials, OP has no way to unlock it (perhaps their employer can, using the old user's password).

Deleting the old data volume will not erase the user's files stored in the current macOS install; it will delete the content from the old one. If the employer needs that previous data, then they would have to provide the previous user's password to access it. Otherwise, if the previous data is not needed, then it should be safe to delete the old data volume.

Arcielee, if you haven't deleted the old data volume yet, it might be best to double-check that the previous user's content is not needed. My mistake for not mentioning that.

Encryptor5000-

You seem to have omitted the very important warning that deleting a MacOS volume MAY ERASE all the User's files, with no hope of Recovery.

Perhaps you could clarify a little more...