To make a duplicate copy of a file, use the command cp. For example, to create an exact copy of the file called firstfile, you would type:
cp firstfile secondfile
This results in two files with different names, each containing the same information. The cp command works by overwriting information. If you create a different file called thirdfile and then type the following command:
cp thirdfile firstfile
you will find that the original contents of firstfile are gone, replaced by the contents of thirdfile.