Catalina wont boot from external SSD

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Catalina wont boot from external SSD

My late 2012 iMac is now running from an external Samsung SSD. It runs fine, but I wanted a more robust drive so I got a OWC SSD 1TB drive and a Mercury Elite Pro Mini enclosure. I have the OWC connected with USB 3. I have downloaded a fresh copy of Catalina from the App store onto the drive, but when it comes to rebooting (picture of keyboard and mouse on screen) it looks like it goes to an old installer or something, because it just hangs and doesn't move. The original HD on the Mac is just used for Time Machine backups now. Could it still have an old installer confusing things?

It worked fine with my Samsung, but not with my OWC, which is, btw, erased and formatted as APFS, same as the Samsung.

What would make this work? Cloaning? Bootable drive?

Thanks in advance.

iMac 21.5", macOS 10.15

Posted on Feb 19, 2020 5:46 PM

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Answer 1

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leroydouglas

Community+ 2024

Level 10

188,682 points

Feb 20, 2020 7:46 AM in response to socal59

socal59 wrote:

My late 2012 iMac is now running from an external Samsung SSD. It runs fine, but I wanted a more robust drive so I got a OWC SSD 1TB drive and a Mercury Elite Pro Mini enclosure.

I have the OWC connected with USB 3. I have downloaded a fresh copy of Catalina from the App store onto the drive, but when it comes to rebooting (picture of keyboard and mouse on screen) it looks like it goes to an old installer or something, because it just hangs and doesn't move. The original HD on the Mac is just used for Time Machine backups now. Could it still have an old installer confusing things?

It worked fine with my Samsung, but not with my OWC, which is, btw, erased and formatted as APFS, same as the Samsung.

What would make this work? Cloaning? Bootable drive?

Thanks in advance.

You can clone from one external USB drive to another external USB drive (Daisy chaining.)

No need for a fresh install, if you are currently not having issues.

Make a bootable clone of your main macOS drive that you are booted to (ie up and running)

to your new OWC SSD 1TB drive—and pickup right where you left off.

Use Carbon Copy Cloner—there is a trial version

ref: Boot clone https://discussions.apple.com/docs/DOC-10081

If you want a bootable USBinstaller of macOS Catalina, this can be done on a flash drive larger than 12GB

How to create a bootable installer for macOS - Apple Support

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Answer 2

socal59 Author

Level 1

20 points

Feb 20, 2020 4:24 PM in response to leroydouglas

leroydouglas wrote:

You can clone from one external USB drive to another external USB drive (Daisy chaining.)

No need for a fresh install, if you are currently not having issues.

Make a bootable clone of your main macOS drive that you are booted to (ie up and running)

to your new OWC SSD 1TB drive—and pickup right where you left off.

Use Carbon Copy Cloner—there is a trial version

ref: Boot clone https://discussions.apple.com/docs/DOC-10081

If you want a bootable USBinstaller of macOS Catalina, this can be done on a flash drive larger than 12GB

How to create a bootable installer for macOS - Apple Support

@leroydouglas, I tried the free trial of Carbon Copy Cloner. I rebooted with the copy and it went back to the mouse/keyboard page. I did a hard reset and chose the OWC drive and it took a little bit of time, but finally booted. It seems to be working.

Something in Catalina that makes booting up on an external SSD hit a wall and you have to reboot.

Anything you need to do to a carbon copy drive, like reinstall OS or anything to make sure all is Apple perfect?

Thanks for the tip. Fingers crossed it works for a while.

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Answer 3

poikkeus1

Level 4

2,467 points

Feb 19, 2020 6:24 PM in response to socal59

Contact OWC with your questions. Their customer support team should be able to provide you with the specific answers you're looking for.

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Catalina wont boot from external SSD

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