I used the following commands to create a bootable Ubuntu thumbdrive using OS X.
First, I ran the following command to find my thumbdrive after connecting it to my computer.
In this case, my thumbdrive was
Next, I converted the Ubuntu disk image from
hdiutil convert -format UDRW -o ~/Downloads/ubuntu-12.04.3-desktop-amd64.img ~/Downloads/ubuntu-12.04.3-desktop-amd64.iso
I unmounted the thumbdrive
diskutil unmountDisk /dev/disk1
and then wrote the image to the thumbdrive
sudo dd if=~/Downloads/ubuntu-12.04.3-desktop-amd64.img of=/dev/rdisk1 bs=1m
After it was finished writing, I ejected the thumbdrive
diskutil eject /dev/disk1
After this, I was able to plug the drive into a laptop and boot into Ubuntu with no issues.