Imac stuck in OS X Base System

[Tyrrelll]

Hi guys, I’m sure this has been mentioned before but I’m really hoping someone can help.

I bought a second hand 2017 imac and as it had a load of rubbish on there from the previous owner I wanted to do a fresh install. After erasing the hard drive I am getting the following error when trying to reinstall macOS ‘the operation couldn’t be completed. Permission denied’ I believe this to be because my entire fusion drive is now ‘OS X Base System’ and I am unable to erase this again as it’s greyed out (see screenshot) I have also tried to partition this but it keeps failing. Essentially I have no ‘Macinto HD’ and I believe that is why I can’t install macOS. I’m pretty stuck, can anyone help?

 

[jerwin]

https://support.apple.com/en-us/HT201314

specifically:

Newer Mac computers and some older Mac computers automatically try to start up from macOS Recovery over the Internet when unable to start up from the built-in recovery system. When that happens, you see a spinning globe instead of an Apple logo during startup. To manually start up from macOS Recovery over the Internet, hold down Option-Command-R or Shift-Option-Command-R at startup.

If you still can't start up from macOS Recovery, and you have a Mac that is able to start up completely, you might be able to create an external Mac startup disk to start up from instead.