How to place a bootable ISO on a USB drive

This is an interesting question. I can see it being very useful to have a single USB "master" LiveCD, instead of having so many different DVDs and pen-drives scattered around.

There seem to be a number of different approaches to this, all of them doable:

• Mk-boot-usb: a Script to Create Multiple-Bootable USB Sticks
• Boot Multiple Distro from USB / Flash drive / Pendrive
• Booting multiple LiveCD's from a single USB stick

Directly from the How to install Ubuntu on MacBook using USB Stick page (my formatting):

1. Download the desired file
2. Open the Terminal (in /Applications/Utilities/ or query Terminal in Spotlight)
3. Convert the .iso file to .img using the convert option of hdiutil (e.g., hdiutil convert -format UDRW -o ~/path/to/target.img ~/path/to/ubuntu.iso)
4. Note: OS X tends to put the .dmg ending on the output file automatically. Remove the .dmg extension as necessary, mv ~/path/to/target.img{.dmg,}
5. Run diskutil list to get the current list of devices
6. Insert your flash media
7. Run diskutil list again and determine the device node assigned to your flash media (e.g. /dev/disk2)
8. Run diskutil unmountDisk /dev/diskN (replace N with the disk number from the last command; in the previous example, N would be 2)
9. Execute sudo dd if=/path/to/downloaded.img of=/dev/rdiskN bs=1m (replace /path/to/downloaded.img with the path where the image file is located; for example, ./ubuntu.img or ./ubuntu.dmg).
10. Using /dev/rdisk instead of /dev/disk may be faster.
    • If you see the error dd: Invalid number '1m', you are using GNU dd. Use the same command but replace bs=1m with bs=1M.
    • If you see the error dd: /dev/diskN: Resource busy, make sure the disk is not in use. Start Disk Utility.app and unmount (don't eject) the drive.
11. Run diskutil eject /dev/diskN and remove your flash media when the command completes
12. Restart your Mac and hold down Alt while the Mac is restarting to choose the USB stick

Note: On newer Macs you might have to install an EFI boot manager to boot from USB.

See also: Download Ubuntu Desktop.