How can I copy data from broken iMac

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Level 1

8 points

How can I copy data from broken iMac

I am trying to help out a friend with their Intel iMac running Monterey. It currently won't boot and hangs part way - tried Disk First Aid but looks like I need to copy data and reformat. They have no back-up (yes, I told them they needed it) so hoped I could use Target Disk with Thunderbolt cable to connect another Mac. The latest OS I have on a Macbook Air is Mojave but when I try this it says the iMac disk is incompatible. I cannot install Monterey on an external HD on the iMac - it says disk needs formatting in AFPS and the HD won't do this in Disk Utility. All I need is to be able to copy the data from the iMac and I can reformat the drive and hopefully fix it, but it seems the changes to disk formatting is making this tricky.

The Mac running Mojave isn't mine, so not keen to update this unless necessary. Any suggestions gratefully received. Thanks.

Posted on Sep 25, 2022 5:11 AM

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Answer 1

Top-ranking reply

Luis Sequeira1

Level 9

67,150 points

Sep 25, 2022 8:44 AM in response to AntF

GUID is a partition map, not a format.

I am guessing that you may just have tried to erase the volume, and not the whole drive.

1) View->Show All Devices

2) Select the whole drive

3) Click Erase.

It may look like this:

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Answer 2

Sep 25, 2022 5:28 AM in response to AntF

Target Disk Mode (TDM) is what I would try too.

From your description, it looks like you tried to boot the other mac using the iMac in TDM. That would be incorrect.

Start the problem iMac in TDM.

Start the other mac from its own system drive.

Connect the two.

The iMac drive should appear in the other mac so you can copy stuff off of it like any other drive.

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Answer 3

AntF Author

Level 1

8 points

Sep 25, 2022 5:45 AM in response to Luis Sequeira1

Hi Luis, I connected the 2 Macs with TB cable. Started the iMac putting it into Target Disk mode but the Macbook Air gets the message saying disk is not compatible, which I assume is connected to formatting. I assumed it would work as lots of info I read said this was the best way but the Mac needed to be running at least High Sierra if the broken Mac had Monterey.

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Answer 4

Sep 25, 2022 6:10 AM in response to AntF

Since the other mac is running Mojave it should work, but for some reason it is not.

Regarding installing on an external drive, you could prepare that in the MacBook Air (format as APFS and install Monterey), and then bring it to the iMac

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Answer 5

AntF Author

Level 1

8 points

Sep 25, 2022 6:11 AM in response to AntF

Just tried another option - formatting the external HD on an older Mac and then plugged it back into the iMac and currently it seems to be installing Monterey onto this. If this works I should be able to boot the iMac. Not sure why but it seems like Apple removed the option for GUID Partition formatting on the iMac, yet still requires this format for making a bootable disk.

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Answer 6

Sep 25, 2022 6:15 AM in response to AntF

Sorry but I think your Air is probably NOT running Mojave.

Please go to the Apple menu, choose About this Mac.

Tell us what it says about the version of macOS (better yet, post a screenshot but do not include the serial number- it appears at the bottom of the window and is considered private information)

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Answer 7

AntF Author

Level 1

8 points

Sep 25, 2022 6:39 AM in response to Luis Sequeira1

Its running 10.14.6 Mojave. Thinking about it I am not sure I tried to format the HD on this machine as I have been through so many configurations of testing, but on the iMac there was certainly no option to use GUID Partition when formatting the HD in Disk Utility. Only HFS (2 versions) + FAT32 and MS.

I did format it on my Mac Pro running El Capitan and will see if I can get Monterey to install and then boot.

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Answer 8

AntF Author

Level 1

8 points

Sep 25, 2022 6:47 AM in response to KiltedTim

Yes, I tried Safe Mode but it hung part way through. I also tried reinstalling Monterey but it also stalled part way through - I left it overnight but the progress bar got about halfway and stayed there. Disk First Aid reports issues and suggests back-up which is the current task and I will erase and try to reinstall the OS. iMac gets very light use and HD is 90% empty, so no issues with disk space.

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Answer 9

Barney-15E

Level 10

116,074 points

Sep 25, 2022 6:56 AM in response to AntF

AntF wrote:

Just tried another option - formatting the external HD on an older Mac and then plugged it back into the iMac and currently it seems to be installing Monterey onto this. If this works I should be able to boot the iMac. Not sure why but it seems like Apple removed the option for GUID Partition formatting on the iMac, yet still requires this format for making a bootable disk.

If you have not select "Show All Devices" from the View Popup menu, you can only select the volume, not the drive. If that drive you are using is not already GUID, you can't change it for just the Volume. You have to select the device and erase that. You would then have the option for GUID Partition Map.

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Answer 10

AntF Author

Level 1

8 points

Sep 25, 2022 7:01 AM in response to Barney-15E

Thanks - that could have been the reason GUID wasn't in the options list when I tried to reformat but on the El Capitan Mac it was available having just selected the drive - maybe they changed the way this displays. I can't check as Monterey is installing, but I will have a look when it completes.

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Answer 11

AntF Author

Level 1

8 points

Sep 26, 2022 3:06 AM in response to Luis Sequeira1

Thanks for the info. All now sorted and Mac is back up and running. Also sorting the proper back-up plan for any future issues.

I have reformatted disks before but when you don't do it often there are quite a few things that trip you up. The fact there seemed to be updated formats for drives and the fact Thunderbolt wouldn't work to transfer files didn't help.

Thanks again.

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