Installing Ubuntu from USB Drive

I know there is a variety of tutorials about installing Ubuntu from a USB drive. Since Ubuntu doesn't provide hybrid disc images, you need to make some extra effort not to waste a CD per release.

What you need is:

• A USB drive (larger than 610 mb) (with no files in it, even so, they will be gone at the end of the progress)
• Boot image specific to release that you are trying to install. You can download boot image for Ubuntu 12.04 Precise Pangolin (amd64): http://archive.ubuntu.com/ubuntu/dists/precise/main/installer-amd64/current/images/hd-media/boot.img.gz
  (You need to replace the parts 'precise' and 'installer-64' matching the release and architecture that you want to install.)
• The ISO file for the release you want to install.

If everything is ready, let's roll:

1. First, make sure that the USB drive isn't mounted.
2. Assuming your USB drive is /dev/sdb (DOUBLE CHECK THIS PART, OR YOU'LL RUIN ONE OF YOUR HARDDISKS!)
   
   # zcat boot.img.gz > /dev/sdb
   
   If you get 'permission denied' at this step change permission before retrying:
   
   # chmod 666 /dev/sdb
   
3. Unplug and then re-plug the USB device. It should be auto-mounted.
4. Now copy the release ISO you downloaded to auto-mounted partition.
5. Umount the partition clicking the eject button next to the partition's name in your file manager.

After following these steps, you should be able to install Ubuntu with that USB drive selecting USB drive on boot menu. I didn't have chance to test but the same method would probably work for Debian ,too, of course with related boot image and ISO.