How to write u disk from img in mac os x

Mac OS X

Command Line Interface

• Download the desired .img file
• Open a Terminal (in /Applications/Utilities/)
• Run diskutil list to get the current list of devices 
• Insert your flash media
• Run diskutil list again and determine the device node assigned to your flash media (e.g. /dev/disk2) 
• Run diskutil unmountDisk /dev/diskN (replace N with the disk number from the last command; in the previous example, N would be 2) 
• Execute sudo dd if=/path/to/downloaded.img of=/dev/rdiskN bs=1m (replace /path/to/downloaded.img with the path where the image file is located; for example, ./ubuntu.img, /dev/rdiskN is faster than /dev/diskN). If you see the error dd: Invalid number `1m', you are using GNU dd. Use the same command but replace bs=1m with bs=1M. 
• Run diskutil eject /dev/diskN and remove your flash media when the command completes