Unmount the card before cloning by running:
(replace sdd1 to your sd card’s name).
To check the name of sd card:
sudo fdisk -l
This is the command to copy to sd card.
dd bs=4M if=2016-09-23-raspbian-jessie.img of=/dev/sdd
First we will copy the content of first image to local directory by running:
dd if=/dev/sdc of=sdimage.img bs=4M
Then copy the image to 2nd sd card.
dd if=sdimage.img of=/dev/sdc bs=4M