Creating a bootable USB Stick on Mac OS X from an ISO Image

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This is actually just a copy of an article from ubuntu.com, but they tend to move things around and I like to have short search times. Apart from that, this works for FreeBSD and even for Windows (tested with Windows 7) as well. Sorry for this this blatant plagiarism, but it might be also to your advantage ;)

One more note: If you want to create a bootable USB stick to be used on a Mac/OS X, do not forget to format the stick with Disk Utility to HFS+ with a GUID partition table.

In case you want to create a bootable USB stick for OS X Mavericks / OS X Yosemite, there exists a shortcut command (note to change the target disk folder accordingly):
sudo /Applications/Install\ OS\ X\ Mavericks.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ Mavericks.app --nointeraction

To create an USB stick for general usage:

  • Download the ISO image in question
wget http://somewhere.org/input.iso
  • Convert the ISO image using hdiutil
hdiutil convert -format UDRW -o output input.iso
  • Check the device number of your USB stick, e. g. by
diskutil list
  • Unmount the key without ejecting it with
diskutil unmountDisk /dev/diskN

, where N is the device number acquired previously

  • Move the image onto the key using
sudo dd if=output.dmg of=/dev/rdiskN bs=1m

Note that using /dev/rdiskN might be faster than /dev/diskN and bs=1m is required since dd would otherwise block forever.

  • Eject the key with
diskutil eject /dev/diskN

Mind the small changes from the original ;) If you now want to start from the bootable USB key, leave it plugged in your Mac, reboot and press Alt/Option (⌥) before the Apple logo occurs.

Cheers,
iss

nesono