sparpart Author

Level 1

9 points

Verify or Erase of external disk fails

I cant't verify, mount or erase an external disk:

diskutil verifyDisk /dev/disk2

Started partition map verification on disk2

Checking prerequisites

Problems were found with the partition map which might prevent booting

Error: -69808: Some information was unavailable during an internal lookup

diskutil unmountDisk force /dev/disk2

Forced unmount of disk2 failed: at least one volume could not be unmounted

diskutil eraseDisk APFS 1TB GPT /dev/disk2

Started erase on disk2

Unmounting disk

Error: -69877: Couldn't open device

I turned off Spotlight:

sudo mdutil -i off /dev/disk2

Spotlight server is disabled

Diskutil list output:

/dev/disk2 (external, physical):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *1.0 TB disk2

1: EFI EFI 209.7 MB disk2s1

2: Apple_APFS Container disk3 1000.0 GB disk2s2

/dev/disk3 (synthesized):

#: TYPE NAME SIZE IDENTIFIER

0: APFS Container Scheme - +1000.0 GB disk3

Physical Store disk2s2

1: APFS Volume Preboot 33.5 MB disk3s2

2: APFS Volume Recovery 526.8 MB disk3s3

3: APFS Volume VM 1.1 GB disk3s4

4: APFS Volume Macintosh HD 2 - Daten 425.5 GB disk3s

5: APFS Volume Macintosh HD 2 11.5 GB disk3s6

I lost in all possible ways of reformating, repartitioning, etc.

Could someone give me a hint how to continue?

I'm not a newbie, but also no hardware genius ... :-(

MacBook Pro 13″

Posted on Mar 5, 2023 3:15 AM

Top-ranking reply

ryane77

Community Specialist

Posted on Mar 7, 2023 8:29 AM

Hey sparpart,

We’d be happy to help out. Looks like you're having an issue working with an external hard drive, correct?

Did you do this process through macOS Recovery, or from the desktop? If you tried it from the desktop, you might instead want to boot into macOS Recovery to try it there: Intro to macOS Recovery - Apple Support

The exact steps to reach macOS Recovery will depend on the processor you use:

"Depending on the type of Mac you have, refer to one of the following to learn how to start up your computer in macOS Recovery and use its apps and utilities:

Once you reach macOS Recovery, test Disk Utility and let us know how it goes.

Take care!

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6 replies

Top-ranking reply

ryane77

Community Specialist

Mar 7, 2023 8:29 AM in response to sparpart

Hey sparpart,

We’d be happy to help out. Looks like you're having an issue working with an external hard drive, correct?

The exact steps to reach macOS Recovery will depend on the processor you use:

"Depending on the type of Mac you have, refer to one of the following to learn how to start up your computer in macOS Recovery and use its apps and utilities:

Once you reach macOS Recovery, test Disk Utility and let us know how it goes.

Take care!

Mar 9, 2023 8:51 PM in response to sparpart

It can be very difficult sometimes with macOS to determine what process is still accessing a volume. I have used the following two command line utilities "fs_usage" and "lsof". I don't recall the specific options I used with either command.

Or perhaps the drive has a hardware issue of some sort.

You can try erasing the drive using Windows or Linux, then connecting it back to the Mac in order to use Disk Utility to erase it again. macOS and Disk Utility sometimes just get stuck if something unexpected is encountered.

sparpart Author

Level 1

9 points

Mar 6, 2023 9:41 PM in response to sparpart

For some reason the drive cannot be unmounted or erased.

From my limited understanding this can either be due to some open files or processes blocking the umount or a defect partition table (GPT).

Maybe someone can help me figuring out the reason?

sparpart Author

Level 1

9 points

Mar 8, 2023 12:29 AM in response to ryane77

Hello ryanne77,

Since I have an Intel-based Mac I have worked carefully through the corresponding Apple manual.

I booted into local + Network Recovery Mode (the one for Catalina) + external boot from a another Harddrive.

I also removed the internal Harddrive from my MBP 2012 and attached it with a docking station via usb.

From there I tried all proposed ways of erasing the disk and installing a new OS.

I disabled SIP.

Tried to Verify, Unmount or erase the HD with the disk utility.

Ran diskutil from the terminal and repeated erase, verification an portioning from there.

No success.

I pasted the command lines output already above.

Regards, Stefan

sparpart Author

Level 1

9 points

Mar 8, 2023 3:40 AM in response to sparpart

Hello Ryanne77,

following is part of the output from a Linux Test App; there's more data if you need:

=== START OF INFORMATION SECTION ===

Model Family: Samsung based SSDs

Device Model: Samsung SSD 850 EVO 1TB

Serial Number: S2RFNXAH121261H

LU WWN Device Id: 5 002538 d40a1047e

Firmware Version: EMT02B6Q

User Capacity: 1,000,204,886,016 bytes [1.00 TB]

Sector Size: 512 bytes logical/physical

Rotation Rate: Solid State Device

Form Factor: 2.5 inches

TRIM Command: Available

Device is: In smartctl database [for details use: -P show]

ATA Version is: ACS-2, ATA8-ACS T13/1699-D revision 4c

SATA Version is: SATA 3.1, 6.0 Gb/s (current: 3.0 Gb/s)

Local Time is: Wed Mar 8 11:17:33 2023 CET

SMART support is: Available - device has SMART capability.

SMART support is: Enabled

AAM feature is: Unavailable

APM feature is: Unavailable

Rd look-ahead is: Enabled

Write cache is: Enabled

DSN feature is: Unavailable

ATA Security is: Disabled, NOT FROZEN [SEC1]

=== START OF READ SMART DATA SECTION ===

SMART overall-health self-assessment test result: PASSED

sparpart Author

Level 1

9 points

Apr 4, 2023 3:27 AM in response to HWTech

Thanks for the help!

I tried to rescue the ssd using linux tools, but so far in vain. This is probably something for experts, which I‘m obviously not :-(

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Verify or Erase of external disk fails