Connect two SD cards to one Arduino board and copy from one to another
You can't do it with your Arduino-Uno (and usual SD libraries).
SD cards are organized in 512 byte &quot;sectors&quot;. You need at least one sector for the file system itself and one sector for the data. If you try to have two files open simultaneously, all your 2048 bytes RAM are required for the SD buffers and you can't return from the file open() call any more.