Cloning an IMG
Identify the volume to clone to.
This is what
diskutil list returns with no external volumes. Yours could be different but is probably similar. Don't use these or you could accidentally do some damage.
After inserting a micro SD card.
/dev/disk2 as the volume to image.
Unmount the volume
diskutil unmount /dev/disk2 # or diskutier unmountDisk /dev/disk2
Brief Info on dd Command
The dd utility copies the standard input to the standard output. Input data is read and written in 512-byte blocks. If input reads are short, input from multiple reads are aggregated to form the output block. When finished, dd displays the number of complete and partial input and output blocks and truncated input records to the standard error output.
if=/PATH/FROM : Input File or the file you want to copy to.
of=/PATH/TO : Output File or where to image the file to.
bs=1M : Block Size This all kind of depends on what the volume is and how fast read and write can happen. Usually this is safe. It's just saying write 1 MB at a time pause for data write then do another MB.
Begin the clone using
sudo dd of=~/Downloads/2015-05-05-raspbian-wheezy.img if=/dev/disk2 bs=1m
Another example when I made an image of CentOS 7 to a SSD.
diskutil list diskutil unmount /dev/disk3 cd ~/Downloads sudo dd if=CentOS-7-x86_64-Everything-1503-01.iso of=/dev/disk3 bs=1m