Fedora does it; OpenSUSE does it and now Ubuntu will also be distributed as a hybrid ISO. Many RPM distributions have been releasing their ISOs in the hybrid format for quite sometime now. Colin Watson of Canonical has announced yesterday that all the amd64 and i386 ISO for Ubuntu 11.10 Oneiric Ocelotwill be distributed in the hybrid format starting today.
What is a hybrid image?
Ubuntu users must be aware that whenever a new version of Ubuntu is released, it is made available as an ISO file. That file can be burned to a CD directly and the CD can be used to boot into an Ubuntu live environment and to install Ubuntu to the hard disk if the user desires. However if users wanted to install using a USB flash drive, they had to rely on a special application the Start-up Disk Creator.
With a hybrid image, users do not need the Start-up Disk Creator. If they want to boot using a USB flash drive, they can simply copy the contents of the image file into the USB drive. Of course, hybrid image can still be burned directly to a CD.
Why was Ubuntu so late in adopting hybrid image?
As mentioned above, many other Linux distributions have been releasing hybrid ISOs for quite a while now. Ubuntu could not switch over to the hybrid images because, like Debian, Ubuntu was using jigdo downloads. Switching to a hybrid image will break jigdo.
Debian switched over from jigdo to xorisso in January because xorisso works with hybrid images. And now Ubuntu too has decided to switch over to xorisso and distribute hybrid images after all Ubuntu is a Debian derivative.
What does this mean for users?
For those who uses the image files by burning it to a CD, this means absolutely nothing for them. Everything will work as it has always worked.
For those who prefers USB flash drives to CDs, this means that the Ubuntu Start-up Creator is no longer needed. All that is needed to make a bootable USB drive is the dd command. Here is the syntax for the command:
dd if=<image_name> of=/dev/sdX
<image_name> is the name of the hybrid image you have downloaded and sdX is your USB drive.
Right now I do not think that there is no GUI application to do this. But before the release of Ubuntu 11.10, I expect to see one.