Create Ubuntu Bootable USB Drive

Download the desired version of Ubuntu

Ubuntu.com

Convert the .iso file format into an .img file

hdiutil convert -format UDRW -o ~/Path-to-IMG-file ~/Path-to-ISO-file

When the image file is complete it will actually end up as a .dmg file.

Get the device number and unmount the USB drive

diskutil list

Usually the last disk connected will show up last in the list, ie /dev/disk3 or /dev/disk3

Then unmount the USB disk with the following command where N indicates the number found with the previous command.

diskutil unmountDisk /dev/diskN

When the disk unmounts a confirmation message will appear.

Unmount of all volumes on disk12 was successful

Create a bootable USB drive from the Ubuntu image

To create the disk, issue the following command. Note when writing to the disk path we will prepend the disk name with an r to indicate raw transfer.

sudo dd if=/Path-to-IMG-DMG-file of=/dev/rdiskN bs=1m status=progress

When the USB disk creation is complete your operating system may prompt you that a new disk was inserted. Do not Initialize, Ignore or Eject it just yet. Return to the terminal and eject the USB drive by running the command:

diskutil eject /dev/diskN