From Fedora Project Wiki

On occasion, you may be asked to use an updates disk image. We use these images to test out fixes and as a way to distribute fixes without having to make entirely new sets of installation media. Basically, the updates.img is a file with an ext3 filesystem on it that you can use. Just about anything can be distributed via an updates.img - new Python files, updates libraries that the installer requires, and so forth. Anything in the updates.img overrides what comes on your installation media.

How you use an update disk depends on how you're installing. For all installation methods, you can use a floppy disk. In this case, you need to write the updates.img out to a floppy. Under Linux, you can write the floppy outline so:

dd if=updates.img of=/dev/fd0

On Windows, you'll need to use the rawrite utility. Then once you have the floppy made, you need to put it into the drive and enter the following at the boot prompt:

linux updates

You can also store the updates.img on a remote FTP or HTTP site and provide anaconda with the location. This works for all installation methods and is often the easiest way to do it. If you knew the updates.img was stored at http://someserver/dir/updates.img, you would enter the following at the boot prompt:

linux updates=http://someserver/dir/updates.img

The AnacondaOptions page more thoroughly explains all the possible values for the updates parameter.

If you are installing from an NFS, HTTP, or FTP server that you run, you can simply place the updates.img file into the /Fedora/base directory. The file will automatically be detected by the installer. If you do not run the server you're installing from, you will have to use the floppy method described above.

If you are installing from a CD or DVD, obviously you cannot easily add files to /Fedora/base. If you are determined to do this though, you can copy the contents of the first disc to a directory, add your updates.img into /Fedora/base, remake the CD or DVD image, and burn it to new media. The big problem here is that it's not nearly as flexible as the other methods. If you need to test out another change, you'll have to go through this procedure all over again.

If you are installing from CD images stored on a drive (whether that's a local drive or on a server somewhere), you can use the floppy or remote URL method or explode the first CD image, copy the updates.img into /Fedora/base, and remake the CD image. This is easier than the physical CD/DVD method because you don't have to copy the contents of the media over and then later burn new ones, but it's still not very flexible.

We may sometimes provide updates images shortly after a release. These usually contain fixes for a variety of bugs that are found just after release and are commonly reported. In this case, we will link to the updates image and this document in the bug reports for bugs that are fixed.