Accidently deleted Bootcamp from DU and now can't start Mac OS

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Level 1

4 points

Accidently deleted Bootcamp from DU and now can't start Mac OS

So I made a really dumb mistake and deleted my mac partition in DU instead of going through Bootcamp Assistant. Nothing happened at the time but upon restarting my Mac I got the infamous folder with the question mark. I did the Internet Recovery and entered OS X Utilities. It appears all my data and files are on my original partition still so I didn't lose them and after verifying it, it appears ok.

My question is, how do I get my Mac OS back from here without losing my data? Will going 'Reinstall OS X' do a fresh install and delete my data? I also don't have a backup, which is worrying.

I also do want to get my full 500gb for my Mac OS but I'll deal with this problem first.

Thanks for any help

Posted on Oct 27, 2020 3:57 AM

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Answer 1

thwaitesy Author

Level 1

4 points

Nov 2, 2020 12:56 PM in response to Loner T

Thank you.

When I ran diskutil repairDisk disk0, it says

Repairing the partition map might erase disk0s1, proceed? (y/N)

Is this ok?

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Answer 2

Loner T

Level 9

59,536 points

Nov 2, 2020 8:16 PM in response to thwaitesy

Yes.disk0s1 is the EFI partition on the internal disk. It can be rebuilt, if necessary.

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Answer 3

thwaitesy Author

Level 1

4 points

Nov 3, 2020 6:22 PM in response to Loner T

This is what I get once booting up, UNTITLED is my external drive

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Answer 4

thwaitesy Author

Level 1

4 points

Nov 4, 2020 3:07 PM in response to Loner T

Thanks, I did step 1 and then went on to step 2. Seems like it is still greyed out

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Answer 5

Loner T

Level 9

59,536 points

Nov 12, 2020 2:57 PM in response to thwaitesy

Excellent!

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Answer 6

Loner T

Level 9

59,536 points

Oct 28, 2020 5:37 AM in response to thwaitesy

Usually, I use a USB3 Flash drive/HDD. USB2 can be slow. We should try and match the macOS version on the internal disk and the external disk. The Disk Utility versions can be different for different versions macOS. It is not recommended that an older version be used to manipulate a disk with a newer version of Disk Utility.

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Answer 7

Loner T

Level 9

59,536 points

Nov 4, 2020 7:45 AM in response to thwaitesy

From a file system perspective your internal disk seems to be fine.

My recommendation is

Install GPT Fdisk, so the partitioning issues can be corrected. These are related to Recovery HD and the HFS+ Bootcamp partition.
Since you already have copied important files, re-install Sierra on the internal disk, without erasing the disk or Macintosh HD, which will preserve non-OS files.
Once macOS Sierra from the internal disk is bootable, run BC Assistant and Remove/Restore the Bootcamp partition to get the disk space back in the macOS part.

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Answer 8

Loner T

Level 9

59,536 points

Nov 4, 2020 8:22 PM in response to thwaitesy

You can use

diskutil cs revert disk1

This will remove the CoreStorage encapsulation and make the disk0s2 as Apple HFS+.

Here is usage for the command.

diskutil cs revert

Usage:  diskutil coreStorage revert

        MountPoint|DiskIdentifier|DeviceNode|lvUUID

        [-stdinpassphrase | -passphrase [passphrase] | -recoverykeychain file]

Convert a CoreStorage logical volume back to its native type.

If you are attempting to revert a disk on which conversion was started but

which could not be unmounted, you must eject the disk or reboot first.

The file system must be mounted and resizable (i.e. Journaled HFS+).

Ownership of the affected disk and a passphrase (if encrypted) is required.

Then you can check if Sierra can be installed on Macintosh HD on the internal disk.

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Answer 9

thwaitesy Author

Level 1

4 points

Nov 11, 2020 4:32 PM in response to Loner T

Did that and it worked. Everything is back to normal

Thanks so much for your help. You went above and beyond! I will now keep regular backups and won't jump into doing something like that again without looking it up.

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Answer 10

Loner T

Level 9

59,536 points

Nov 3, 2020 6:56 AM in response to thwaitesy

A bit concerned about this

Invalid Disk Label @ 404358651904: cksum mismatch

Are you able to see files on the internal disk via macOS Finder?

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Accidently deleted Bootcamp from DU and now can't start Mac OS

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