How do I delete a file even root user can't delete?
I downloaded the Mac OS Catalina installer to my Mac mini running Big Sur. After copying it to an external disk, I deleted the file. When I empty the trash, Finder says that the file is in use. I have restarted the system, even logged in as root, but I can't delete the file.
When logged in as root, I can't even change permission on the InstallESD.dmg-file.
I have also tried the rm -R-command in terminal. Operation is not permitted is the response.
Any suggestions on how I can get rid of this file?
Mac mini 2018 or later