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Error: -69877: Couldn't open device

I had a external USB HD NSFT formatted. I used DiskUtil for erase and get a OSX disk in HFS+ but after i try to do it, I could not mount the disk and I could not format again.

I try with the terminal > diskutil list and I get:

/dev/disk3 (external, physical):

#: TYPE NAME SIZE IDENTIFIER

0: FDisk_partition_scheme *500.1 GB disk3

1: Apple_HFS 500.1 GB disk3s1

after I tried:

iMac :~ col$ diskutil eraseDisk JHFS+ UntitledUFS disk3

Started erase on disk3

Unmounting disk

Error: -69877: Couldn't open device

also

iMac:~ col$ diskutil eraseDisk JHFS+ UntitledUFS /dev/disk3

Started erase on disk3

Unmounting disk

Error: -69877: Couldn't open device

I can't erase or format my disk.

Any idea?

Posted on Nov 29, 2019 8:27 AM

Best reply

MichelleT18

Community Specialist

Posted on Dec 2, 2019 5:32 PM

Hello francos,

Welcome to Apple Support Communities. It sounds like you're seeing an error message when attempting to mount your external drive. I'd be happy to provide information that may help.

First, start up in safe mode to see if the issue persists in safe mode: Use safe mode to isolate issues with your Mac.

Next, test the issue in another user account: How to test an issue in another user account on your Mac.

Another step to try is to turn off FileVault temporarily: Use FileVault to encrypt the startup disk on your Mac.

Take care.

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Error: -69877: Couldn't open device

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