Installing OS High Sierra on an external hard drive

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Level 1

8 points

Installing OS High Sierra on an external hard drive

I've been trying to install High Sierra on an external hard drive and I can't seem to get a proper install. I downloaded the OS X Installer for High Sierra (the full 5 GB version), and I used Disk Utility to erase the external hard drive selecting the Mac OS Journaled and GUID Partition Map options for the drive. I named the hard drive and then executed the Installer. I selected the hard drive, a SP Armor A30, as the destination disk for the install, entered my administrator password and clicked install. After a few minutes a message comes up saying I need to restart my desktop iMac (fall, 2014 model running OS Yosemite 10.10.5). The message also says the install process will continue upon restart and may take a while. After a restart process lasting about 3-4 minutes, I get a log in screen for my desktop, just like normal. There is no option for using High Sierra as a startup disk under System Preferences indicating Sierra is not available as an OS. On the Armor A30 drive itself, there is a folder 'macOS Install Data' that contains a number of .dmg files as well as several other files ending in 'chunklist.' It does not appear the a functioning High Sierra operating system was created during the install process. I have no idea why.

Can anyone offer some ideas for what is happening and how to achieve a successful install? I need the new OS to use a home medical device that will only work with OS X 10.12 or higher.

Thanks for your suggestions.

Posted on Aug 24, 2019 11:13 AM

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Answer 1

fuzzymo

Level 4

2,030 points

Aug 24, 2019 1:03 PM in response to MojaveBlues

Restart your iMac and hold down the Option key until icons of your startup disks show up side by side in the middle of the screen. See if your High Sierra volume is there. If it is select it and restart.

How to select a different startup disk - Apple Support

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Answer 2

MojaveBlues Author

Level 1

8 points

Aug 24, 2019 1:10 PM in response to fuzzymo

Yeah, I did this, and the High Sierra OS does not show up as an available start up OS after the installation process. This tells me that it must not have installed properly. Wish I understood why. There was never a message at any time that there was a problem with the installation process. I've repeated the process about 10 times now, always with the same result. I also downloaded the app Install Disk Creator and still had the same end result when I used it. I have a Genius Bar about an hours drive away, but I'm hoping I can figure this out on my own.

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Answer 3

MojaveBlues Author

Level 1

8 points

Aug 25, 2019 4:16 PM in response to fuzzymo

Well, APFS doesn't look like an option. The SP Armor destination disk is not an SSD drive or a flash drive. When I go to erase the external hard drive in Disk Utility, APFS is not shown as an option, probably because my current OS is not High Sierra, and the external hard drive itself is not the correct type for APFS. Thanks for the suggestion, however.

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