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Multiple Macintosh HD after reinstall

Two years after having bought my MacBook Air I decided it was time for a fresh reinstall. So I took the usual steps: Command-R and erasing of the Macintosh HD, and then reinstall of Big Sur.


Everything seems to be working fine now, but I noticed in Disk Utility that the HD looks somewhat odd. There's the first Macintosh HD which has this weird "com.apple.os.update etc." subsection to it. And then there are two other Macintosh HDs labeled Data.


Anyone has any idea of the what the heck has happened?


Posted on Jul 11, 2021 8:39 AM

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Question marked as Top-ranking reply

Posted on Jul 11, 2021 11:39 AM

Re do the erase and reinstall but erase your disk properly.

Boot to your Recovery HD or bootable USB whichever method you use for reinstalling.


Open Disk Utility, click on View in the menubar and select Show All Devices.

Highlight the Disk (Apple SSD or similar) not any of the indented Volumes.

Click Erase.

Give the Disk a name.

Format: APFS.

Scheme: GUID Partition Map.

Click Erase.

When Done quit Disk Utility.

Reinstall the OS.

3 replies
Question marked as Top-ranking reply

Jul 11, 2021 11:39 AM in response to Rubin_22

Re do the erase and reinstall but erase your disk properly.

Boot to your Recovery HD or bootable USB whichever method you use for reinstalling.


Open Disk Utility, click on View in the menubar and select Show All Devices.

Highlight the Disk (Apple SSD or similar) not any of the indented Volumes.

Click Erase.

Give the Disk a name.

Format: APFS.

Scheme: GUID Partition Map.

Click Erase.

When Done quit Disk Utility.

Reinstall the OS.

Jul 11, 2021 8:58 AM in response to Rubin_22

I believe what happened is when you decided to erase and reinstall Big Sur you ONLY selected the Macintosh HD and erased it - leaving the Data volume. Then when you reinstalled macOS it created a 2nd Data volume. You can get rid of the 2nd Data volume via Disk Utility but you need to be careful and select the correct one. You will need to look into each volume to see which one has your data.


Always erase the VOLUME GROUP when you want to erase your Macintosh HD. This will erase both Macintosh HD and Macintosh HD - Data volumes. In Disk Utility you should see a button to Erase Volume Group when in Recovery Mode.

Multiple Macintosh HD after reinstall

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