installing macOS Sierra on external disk

  rturner003 15:08 16 Sep 2018

I have a macbook pro with High Sierra installed. I want to install macOS Sierra on an external disk and keep getting the same problem. I downloaded a copy on line via the Apple website. This tries to install it automatically but fails because I got High Sierra installed (which is what i want). I places a copy of Install MacOS in the applications folder. I erase my external disk to the correct format and name it Sierra. I then use Terminal and the following command: sudo /Applications/Install\ macOS\ --volume /Volumes/sierra --applicationpath /Applications/Install\ macOS\ when this complete I restart my laptop selecting my external drive as the start disk. It then starts to install Sierra but it fails with a screen with a message: macOS could not be installed on you computer. Volume contains a macOS or OS X installation which may be damaged.

I have tried the whole process three times, including downing the installer app from apple, but i get the same outcome each time.

Has anybody any ideas or suggestion to overcome this

  Pine Man 10:18 18 Sep 2018

It is not High Sierra that I want on it is Sierra the forerunner


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