How can I make an external drive behave as an internal drive? My question is pretty much summed up by the title, I have an external drive which I'd like to have recognized as an internal drive. How can I do that? Thanks for looking at my question. By the way I am running 10.11.3 on mbp
I just found this answer, sorry I tried looking first but couldn't find it....

You should be able to do this with dd by setting Removable to False.

Unmount your disk, then run…

dd if=/dev/zero of=/dev/disk2 bs=1 count=1

Don't forget to replace disk2 with the actual disk identifier. 

This command will erase the contents of the disk. Untested, be careful, usual 'not responsible if stuff goes wrong' applies :)