Can't erase Late 2015 iMac. Error = 654 (kextcache)…Couldn’t unmount disk. :(-69888)

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Can't erase Late 2015 iMac. Error = 654 (kextcache)…Couldn’t unmount disk. :(-69888)

I'm attempting to erase my late 2015 iMac, serial number D2***G7V, to donate to a local charity. Restarted with Command +R, then opened disk utility, and "erase". The erase fails with the above error code. There seems no option here but to destroy this otherwise iMac which is really needed for another purpose. I'm not finding anything online that suggests a work-around. Hoping the support community might be able to identify this issue and recommend a fix. Thanks! Tom

[Personal Information Edited by Moderator]

iMac Line (2012 and Later)

Posted on Apr 17, 2020 5:42 PM

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Answer 1

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den.thed

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82,270 points

Apr 17, 2020 7:04 PM in response to THG

Follow the "erase your hard drive and reinstall macOS" directions in step #6 of > What to do before you sell, give away, or trade in your Mac - Apple Support

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Answer 2

THG Author

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Apr 18, 2020 5:45 PM in response to den.thed

Unfortunately it's Step 6 where the problem starts. I hit erase as indicated in Step 6, and I get the error message "Error =654 (kextcache ...Couldn't unmount disk. :(-69888)". From there no other options to go anywhere. None of the other options on that page leads anywhere, as can't reinstall O/S, can't restore from time machine, etc. I'm hoping someone might recognize the wording of the error message! Thanks, Tom

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Answer 3

BDAqua

Level 10

245,189 points

Apr 18, 2020 6:18 PM in response to THG

Does it still boot up?

Open System Preferences>Accounts, unlock the lock, click on the little plus icon, make a new admin account, log out & into the new account.

In the same pref pane highlight your old account, click the little minus icon, then use Disk Utility to Secure Erase Free Space.

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Answer 4

THG Author

Level 1

10 points

Apr 19, 2020 3:00 PM in response to BDAqua

Your guidance is MUCH appreciated. Two key comments. In "recovery mode" I have only very limited options under the Apple menu. No system preferences. However, I did find that I was able to "restore from time machine". And while it feels a bit quirky still, I do have access now to system preferences. There is no "Accounts", but Users and Groups lists what I believe you may be referring to. There is just on person listed, my name, which is listed as "Admin". I can see where I could add additional users (accounts?) could be added by unlocking, and clicking on plus sign, and adding a new admin user. That would seem to get me to the point I believe you were referencing. If I then go to disk utility, highlight the original user, and Secure Erase Free Space, what would be the next step or steps to correctly erasing the hard drive? Would I do this from the original user account, or the newly added user account? Thanks for any further guidance you're able to provide. Tom

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Answer 5

BDAqua

Level 10

245,189 points

Apr 19, 2020 3:43 PM in response to THG

Very good so far, 1 holdup...

If I then go to disk utility, highlight the original user, and Secure Erase Free Space,

Don't go to Disk Utility to remove the user, in fact, nowI remember Disk Utility had erase Free Space removed, so were left with 2 options...

TechTool Pro that can erase A Folder a number of secure ways, which requires that user be left in place but not logged in.

Or In Sys Prefs Remove the original user then fill the drive by gopying huge nonsense files until nearly ful & deleting them then.

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Can't erase Late 2015 iMac. Error = 654 (kextcache)…Couldn’t unmount disk. :(-69888)

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