They are closer to the physical disk than the buffer cache. dev/rdisk nodes are character-special devices, but are “raw” in the BSD sense and force block-aligned I/O. Since any /dev entry can be treated as a raw disk image, it is worth noting which devices can be accessed when and how. Why? I would try to explain it, but man hdiutil already does so well: Second, the output file value: of=/dev/rdisk2. OS X’s dd command is still a bit dated and doesn’t interpret anything but bytes. You’ll notice a couple of odd things in this command.įirst, the block size value: bs=1048576. When the Ubuntu ISO finishes downloading, you are ready to copy it to the USB drive using dd: sudo dd if=~/Downloads/ubuntu-14.04.3-server-amd64.iso of=/dev/rdisk2 bs=1048576 I am not, nor is anyone else, responsible for any potential data loss. Once you figure out which device the USB drive was mapped to, unmount it ( disk2 is the device in this example, your device will probably be different): diskutil unmountDisk /dev/disk2Ĭopy the Contents of the Ubuntu ISO to the USB Driveĭisclaimer: The following steps will erase everything on your USB drive. Open Terminal and run the following command to figure out which device the USB drive was mapped to: diskutil list Next, plug your USB drive into your Mac it will automatically be mounted by OS X. Start by downloading the Ubuntu ISO you want to boot from.

You can simply download the Ubuntu ISO and use dd to copy it to a USB drive. Ubuntu has a great set of instructions on creating a bootable USB drive in Mac OS X, but they have an additional step I found not to be needed: there’s no need to convert the Ubuntu ISO to an IMG file.

Os x bootable usb