How to un-encrypt my Time Machine back up disk

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How to un-encrypt my Time Machine back up disk

I have an external USB hard drive that I back up to using Time Machine. I've been using the disk for years. I've just noticed in the Time Machine preferences that it says the disk is 'encrypted'. I presume this means that I must have set up a password for the disk so that if someone plugs the disk into a different computer they can not access my files without the password?

Trouble is I can't remember what the password is.

How do I un-encrypt my disk / TM backups?

Do I have to use Disk Utilities to wipe the disk clean and then resume TM? That could take hours...

MacBook Pro 15″, macOS 11.2

Posted on Jun 7, 2021 2:11 AM

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Answer 1

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PRP_53

Level 10

90,997 points

Jun 7, 2021 6:13 AM in response to Sparky Marky

As stated - without the password there is nothing that can be done. To reclaim the space and repurpose the Entire Drive requires a Re-Format as suggested. If you what to leave the space Occupied - leave it alone and create a new APFS Volume on the drive for a New TM Backup.

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Answer 2

PRP_53

Level 10

90,997 points

Jun 7, 2021 4:48 AM in response to Sparky Marky

Will concede to more Learned Contributor on this one - but think without the password to decrypt the drive - the only option is to Wipe the Entire Drive in Disk Utilities. When Wiping the Drive in DU >> View >> View ALL devices and choose the Upper Most name of the Drive to wipe and then choose Erase and format to desired format ( APFS for repurposed TM Backup or HFS Journaled for general usage ) both with the GUID Partition Map.

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Answer 3

Sparky Marky Author

Level 1

47 points

Jun 7, 2021 5:48 AM in response to woodmeister50

FWIW, if there was a way around using a password to decrypt

a disk, it would make encrypting it pretty useless.

Your only option, reformat the drive and start TM all over.

I get that, but on my Mac I have never been asked for the password, so I was hoping for a way to un-encrypt the disk without having to reform it and start again... like make future TM backups un-encrypted and leave older backups encrypted?

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Answer 4

Jun 7, 2021 4:54 AM in response to Sparky Marky

FWIW, if there was a way around using a password to decrypt

a disk, it would make encrypting it pretty useless.

Your only option, reformat the drive and start TM all over.

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Answer 5

PRP_53

Level 10

90,997 points

Jun 8, 2021 4:17 AM in response to Sparky Marky

Welcome and Thank you too !

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How to un-encrypt my Time Machine back up disk

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