download iso file from cents.org
convert iso to img
$hdiutil convert -format UDRW -o target.img CentOS-7.0-1406-x86_64-Everything.iso
umount usb
sudo diskutil unmount /dev/diskX
make usb using dd
time sudo dd if=target.img.dmg of=/dev/disk1 bs=1m
The time command is to display the amount of time the dd command used.
