I than erased the USB and created a new one via the MacDaddy install disk creator. After some more Googling I tried to reset the PRAM with the command option p r keys and booting it up twice. So I selected the USB and went through the process again. After long Googling I found that unplugging and plugging the USB back in while the screen of 'select bootable' was shown, did work. I plugged in the USB to my iMac, held the option key and than the USB didn't show up. It all went well and the USB was located in the Finder as Install macOS Sierra. So I thought that maybe the installer was at fault so I created a bootable USB.įirst I created a bootable USB via my MBP 2016 using the Terminal. After a long time waiting the installer finally ended up with the error: The installation was unsuccesfull, please try again. I rebooted the iMac and went to Recovery and had selected the option to install macOS Sierra.

First of all I erased the HDD via macOS Recovery. This, of course, did not work.Īs there were only old files on the iMac, I decided to perform a clean install. It gave the error that the installation had not been successful and should be run again. Something also notable is that the iMac first failed an upgrade from El Capitan to Sierra via the Mac App Store. As I've tried a lot of things, I'll list them up first as they come with different errors.

The installation comes up with errors every time when it's almost finished. I'm trying to perform a clean install of macOS Sierra on a late 2009 iMac, but I can't get it to work.

Best cleaner for mac os sierra