How to change Time Machine backup drive on macOS 14.6.1

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Level 1

49 points

How to change Time Machine backup drive on macOS 14.6.1

Using MacOS 14.6.1 and a new Seagate 2TB Portable drive and would like to move my backup to the new drive from an older Seagate 4TB which is no longer able to write (but it can be read and be copied from). When I go to Settings, General, Time Machine and try to add the new Drive, everything works up until I get this message "Couldn’t unmount disk". How do I unmount the drive and which drive?

The new drive is showing in Info under Sharing and Permissions that while I presumably have permission to read and write. There is a line under Sharing and Permissions that I can only read. How do I fix this?

I just checked Info on my 4 TB drive and it shows the same thing under Sharing Permissions. What is going on?

Should I upgrade my my system to 15.2?

[Re-Titled by Moderator]

iMac 24″

Posted on Jan 7, 2025 8:47 AM

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Answer 1

John Galt

Level 10

156,224 points

Jan 7, 2025 1:25 PM in response to TRWheaton

TRWheaton wrote:

Using MacOS 14.6.1 and a new Seagate 2TB Portable drive and would like to move my backup to the new drive from an older Seagate 4TB ...

This may no longer be accomplished.

The new drive is showing in Info under Sharing and Permissions that while I presumably have permission to read and write. There is a line under Sharing and Permissions that I can only read. How do I fix this?

You don't, because macOS now renders Time Machine backup drives "read only" which may no longer be changed. Presumably Apple did this because Mac users were unable to abstain from an apparently irresistible temptation to use the Finder to inspect a TM backup volume, which (depending on what they did) tended to corrupt the entire backup volume, making it useless.

You can still use that drive to restore individual items or an entire system, but if you want to keep it in service erase it. It may remain useful for a very long time (years) or it may fail again in a short time. When those failures become intolerably frequent throw it out. Hard disk drives can't be fixed.

Should I upgrade my my system to 15.2?

It won't help. Apple implemented these changes a while ago.

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Answer 2

rkaufmann87

Level 10

148,522 points

Jan 7, 2025 9:04 AM in response to TRWheaton

Google advises:

"To move your Time Machine backups to a new external hard drive (EHD), connect the new drive to your Mac, then go to System Settings > General > Time Machine, uncheck "Back Up Automatically," and select the new drive as your backup disk; you can optionally drag the existing backup folder from the old drive to the new one in Finder before selecting it in Time Machine settings. "

Of course, before executing you need to correctly format your Time Machine drive using Disk Utility. Verify the format type by checking the old External Hard Disk and then use the same format. To check the old External Hard Disk, simply select it in Finder's sidebar and type Command + I and look for the format type. It should be APFS (Case Sensitive).

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