Status of this Process: not working, prepared USB Flash Drive (with the .dmg file processed by hdutil and transferred to USB) is not recognized by the Mac upon startup, even after pressing the option/alt key and going into the startup menu

Running Ubuntu Using USB Flash Drive

Ubuntu 12.04 LTS 32 bit

Convert the .iso file to .dmg using the convert option of hdiutil

In Terminal, type (OS X tends to put the .dmg ending on the output file automatically):

sudo hdiutil convert -format UDRW -o ~/path/to/target ~/path/to/ubuntu.iso

General example:

YOURNAME-MacBook-Pro:~ USERNAME$ sudo hdiutil convert -format UDRW -o ~/IMAGENAME ~/UBUNTUVERSIONNAME.iso

Specific example:

Graham-Robertsons-MacBook-Pro:~ graham$ sudo hdiutil convert -format UDRW -o ~/graham.dmg ~/ubuntu-10.04.2-desktop-i386.iso

Put your USB Flash Drive into the USB port of your Mac (usually at the sides of the mac)(flip the USB flash drive if not fitting)

List the disks connected to your devices. Determine the device node assigned to your flash media (e.g. /dev/disk2)

diskutil list

Unmount your USB flash drive disk by inputting this code:

diskutil unmountDisk /dev/diskN

(replace N with the disk number from the last command; in the previous example, N would be 2)

Specific example:

sudo dd if=/Users/graham/graham.dmg of=/dev/disk2 bs=1m

This step requires patience, as it takes a long time. Wait for Terminal to respond.

Type:

diskutil eject /dev/diskN

Replace "N" with your disk number.

Remove USB Flash Drive

Hold alt/option key while rebooting.