How to install High Sierra on external SSD

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Level 1

24 points

How to install High Sierra on external SSD

I have a new, empty external SSD which is connected to my iMac (late 2011) via Thunderbolt.

I want to use the SSD as a startup disk. To do that, I need to install High Sierra on the SSD.

The only advice I have found on the web is on how to first format the SSD (to apfs) and then clone my internal hard drive to the SSD. This will not work since the SSD is 256 GB and the internal drive is 1TB.

I have no install DVD or any such thing; I need to either download High Sierra from AppStore to the SSD or somehow copy it from my internal hard drive. What will work here?

iMac (27-inch Mid 2011), macOS High Sierra (10.13.2)

Posted on Jan 11, 2018 9:31 AM

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Answer 1

keg55

Level 6

11,755 points

Jan 11, 2018 9:39 AM in response to Eldberg

Download the High Sierra full installer from the App Store to your iMac.

Then install HS to your SSD. IF you want to use the APFS file system then you will instead need to format your SSD APFS before installing HS. To do this you must use High Sierra's Disk Utility. So, if you have HS installed on your iMac you can do it from there before launching the HS installer. Or you will have to make a USB thumb drive installer of HS and boot from it, then format the SSD as APFS from Disk Utility and install HS.

If the SSD were your internal drive then the APFS file system would be automatic. But, you have an external enclosure with your SSD so HS sees this as an HDD and won't auto convert to APFS. This is why you have to manually format it.

After your install of HS, you can use Setup migration to migrate your user accounts, data, apps and settings over to the SSD.

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Answer 2

keg55

Level 6

11,755 points

Jan 11, 2018 9:55 AM in response to Eldberg

Just APFS.

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Answer 3

Eldberg Author

Level 1

24 points

Jan 11, 2018 9:54 AM in response to keg55

Thanks keg55.

I do have HS on the machine and the Disk Utility can format in APFS. But there are several alternatives, I don't know which one to choose. APFS or APFS Shift Sensitive?

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