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Old 07-23-2019, 04:02 PM   #13
odamizu
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Quote:
Originally Posted by pwalker8 View Post
It works. The trick is you need to install High Sierra on the external drive before you upgrade since you can't run the High Sierra installer from a newer version of the operating system.
Thanks! My reason for trying this would be to be able to test an OS before installing it on my primary Mac (which is currently running High Sierra).

Would this be feasible?
  • Install High Sierra on external drive
  • Boot from external drive, then upgrade to either Mojave or Catalina beta or Catalina official release when it comes out. Would Mojave/Catalina on the external drive receive updates through the App Store same as any other Mac? If not, how would I update it?
  • If the new OS works for me, erase/reformat external drive and re-install High Sierra on external drive
  • Upgrade primary Mac to Mojave/Catalina, leaving me with a bootable High Sierra drive to run software that balks on Mojave/Catalina

If it sounds like this may work, I may give it a try.

Quote:
... I actually ended up installing it on a thumb drive that I had. For some reason, the external hard drive was being a bit balky.
What kind of balkiness? I am considering an external SSD drive. Maybe the Samsung SSD T5.

Also, just to make sure I understand, if I boot from an external drive, it's like having a different and separate computer from my primary Mac? I would create new user accounts and re-install apps, just as if it were a new computer?

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