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I just formatted my Macbook Pro. Using macOS Catalina 10.15.4

At boot, I pressed Cmd+R to enter recovery. I then used the disk utils to erase the "Machintosh HD - Data" partition.

I then went over to reinstall the OS and when prompted to choose between "Machintosh HD" and "Macintosh HD - Data", I chose "Macintosh HD". That gave me an error, saying basically that nothing could be installed to that partition. I then retried, but this time used the "Macintosh HD - Data" partition. All good, the OS installed and here I am now... just opened up Disk Utils and I see this mess:

Macintosh HD

Macintosh HD - Data

Macintosh HD - Data - Data

What on earth happend? How can I fix this mess? Screenshots of each partition are above.

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What you have done is upset the logical volume "Macintosh HD".

For security reasons macOS Catalina splits the logical boot volume, in your case "Macintosh HD" into two physical volumes, one for all the system files and another for the use data which has " - Data" put on the end of the name. You've erased half the logical volume, you should have erased either the whole disk or the whole container.

Since your drive is blank the easiest way to fix this is to erase the entire physical device.

To start click the pop up "View" in the top left corner and select "Show All Devices".

Here's what mine looks like.

Disk Utility window

You can see the disk has one APFS container with two physical volumes. The Mac shows these to you as one logical volume.

Now select the drive right at the top (in my case this is "Apple SSD SM1024L Media") and then Erase. Problem gone :)

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  • Hmm the problem is that I don't have a parent container. You can see this in the images. Is this because I need to click that "show all devices" first? My partitions were listed as independent nodes. I did look for the parent container as that's how it looks in all the online examples (as well as on the Apple support website). I only wiped the Macintosh HD - Data partition. Was I supposed to wipe the Macintosh HD partition too? – pookie May 20 '20 at 7:38
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    Update - I went to "View -> Show all devices" and I can now see the parent container and top-level node. Omg. Why is this hidden by default? When I went to format the disk while in recovery mode, the container and parent node were both hidden from view... and it would only let me erase the "Data" partition. I've since installed some programs. Can I make a backup, format and then restore? – pookie May 20 '20 at 10:51
  • @pookie You should be able to make a backup and restore but I put the emphasis on should. I wouldn't be shocked if something went wrong. – Tony Williams May 21 '20 at 22:34
  • No worries. Thanks for your help - I decided to just reformat in the end. All sorted now ;) – pookie May 22 '20 at 23:02

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