Unmounted the internal drive HDD before running the installer. Uninstalled the installer and downloaded fresh.
Unable to unmount volume for repair”įirst time upgrading with the external SSD so I assume this is user error but not sure how to go about fixing this issue. “MacOS could not be installed on your computer. Had no issues installing Sierra but now when I try to install High Sierra it gives the following error: I have a 21.5 iMac late 2013 that boots from an external SSD.
