Struggling to Install external SSD and can’t get recovery or drive boot selection to load

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Level 1

8 points

Struggling to Install external SSD and can’t get recovery or drive boot selection to load

Trying to install and boot from a external SSD as my main drive is a bit flakey and slow. I cannot install on the external drive Catalina.

Tried creating a bootable utility disk https://support.apple.com/en-gb/HT201372 (couldn’t trigger the option key on restart)
Tried entering recovery mode using cmd r, pauses like about to go there but then loads incurrent OS on internal drive
Tried triggering a new install to another external drive, when reboots just reloads the login, even if try the above
Tried using startup disk and click to load a different drive but doesn’t, just loads current OS

Observations

Thought it was my Bluetooth keyboard not allowing me in to a recovery state but same happens with wired one. Thought it might be wrong disk format but using MACOS extended format/also tried APFS When booting Apple logo loads and then see loading bar, this seems longer than on my MacBook but think this is difference between SSD and standard disk

Tried Apple support and not helped to date. Completely stumped

iMac Line (2012 and Later)

Posted on Dec 23, 2020 2:18 PM

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Answer 1

Top-ranking reply

HWTech

Level 9

68,708 points

Dec 24, 2020 6:13 PM in response to Hornbyrob

Sometimes when rebooting after the first install phase the system will boot to the default built-in drive. You may be able to go to Startup Disk System Preferences and select the external drive so the installation completes the second phase. You can also Option Boot and select the orange icon for the external drive which should complete the installation.

If you have trouble Option Booting, then make sure you are timing the key press properly. For older Macs with a startup chime you want to wait until you hear the startup chime before holding down the Option key. For newer Macs without a startup chime you need to hold down the Option key within a second or two at most after pressing the power button. If you hold down the Option key too soon the system may do nothing until you release the key and if you do it too late....well the key won't be recognized. It can be a bit tricky getting used to the quick boot speed of the newer Macs to time this correctly. Same thing holds for Recovery Mode.

If you still have problems Option Booting, then perform a PRAM Reset (hold the PRAM reset for at least three chimes or a full minute so it activates several times - although 2018+ models will only allow one reset). You can also use the Terminal app to clear the NVRAM by using this command:

sudo  nvram  -c

You will be prompted for your admin password. Type it and press the "Return" key to submit it. You won't actually see anything on the screen when typing your password.

Definitely use a wired keyboard since a Bluetooth keyboard may not go ready soon enough to register a boot option key press.

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Answer 2

Hornbyrob Author

Level 1

8 points

Dec 28, 2020 11:35 AM in response to Hornbyrob

One thing I might not have mentioned, I did have a external drive which booted successfully until the install of this latest OS patch. I’d wiped the drive as a last resort thinking I could recovery through recovery mode..

Not necessarily the answer as in part it was due to installing the latest Mac OS as described by William and his post in this thread.

Disconnected hard drives, this allowed me to get in to recovery mode.

Was still struggling to get a install to happen on my external drive.

Partitioned internal hard drive.

On the newly partitioned drive started a install to external drive (after connecting one) worked fine. Can now install and boot.

Really not wanting to reinstall that patch until get some confirmation it will not do the same.

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Answer 3

Barney-15E

Level 10

122,144 points

Dec 23, 2020 7:39 PM in response to Hornbyrob

Does your Mac boot? You should be able to install on the external by running the installer while booted to your flakey internal drive.

Not sure if that was one of the things you tried, but it also sounds like it won't boot at all from an external?

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Answer 4

Dec 24, 2020 6:44 AM in response to Hornbyrob

Similar problems have been reported here in the forum You might try some of the things suggested in this thread:

https://discussions.apple.com/thread/252177156

I had a problem similar to yours, and was able to startup in Catalina from my external SSD by disconnecting all USB devices, except my external SSD (moved it to the first USB port) and resetting NVRAM (several times).

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Answer 5

Hornbyrob Author

Level 1

8 points

Dec 23, 2020 11:50 PM in response to Barney-15E

Mac does boot, when I try to install it to another drive the process starts but on reboot just loads current drive. As you say I can’t trigger it to boot externally.

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