I need to create a bootable USB drive for my partners iMac which is almost ten years older than my current iMac which is running Catalina. I need to create the boot drive to install High Sierra and I can only do this from my machine which is running Catalina.
Is this possible?
iMac 27", macOS 10.15
If you are unable to get and create a bootable High Sierra drive using the Apple Support Article, then you can use DiskMaker X to create one for you. see > https://diskmakerx.com/download/
Note, that there are different DiskMaker X versions depending of which macOS version you want.
Yes, you can do this from your Catalina machine.
Follow this link to find the installer application that you're looking for, High Sierra, I think you mentioned. (?)
How to upgrade to macOS High Sierra
Then follow the instruction linked by @dialabrain in their post above.
edit- actually, the download link is also included in @dialabrain's posted link.
Unfortunately I believe you have missed the most important aspect of making this bootable USB.
My machine is running Catalina and is completely up to date.
I need to make a bootable USB for an older machine—High Sierra.
What you have suggested overlooks this primary detail and will not resolve my issue as it does not seem to be possible to download the actual installer files for any of the OSX systems such as 10.13 High Sierra.
All of the files I have seen available from Apple are the update files which will not work in my situation.
ANOTHERMATTRYAN wrote:
Unfortunately I believe you have missed the most important aspect of making this bootable USB.
My machine is running Catalina and is completely up to date.
I don't believe so.
making a bootable usb drive for an earlier mac osx than is installed on my machine
