You have chosen to install a webui that run on top of a linux OS with no graphical user interface. As the WebUI do not handle anything OS related, you need to learn Linux (more specifically Debian, since Turnkey is a streamlined debian) to be able to maintain your MineOS installation. This is not only reccomended, but an requirement. http://www.aboutdebian.com/
Your error is due to what rights your user has on your system :https://www.digitalocean.com/community/tutorials/an-introduction-to-linux-permissions.
can I just get a fix for this if possible?
Nope. Since this is not a system error. It is the OS that handles users and rights.