I've recently added an SSD drive to my Macbook, and I'm using my HDD to store my files.
Sometimes I want to move a file from my HDD to my SSD though. Whenever I try to drag it, Finder only allows me to copy rather than move.
I've set the permission of both the sending and the receiving folders to Read and Write for my user, but that did not help. When I try to mv using the Terminal it does work without superuser powers.
Best Answer
If the source and the destination of the file is on two different volumes, OS X's default is to copy the file rather than move it. In reality, what you want to do to the file is to copy it to the new location and then delete it from the old, whereas if you move a file to the same volume it's originally on, it will just change the recorded location of the file.
You can achieve "move" (copy-and-delete) functionality in Finder by holding Command when you drag the file.