Another thing that’s been on my list to look at that I’ve finally had time to sit down this week is the new isohybrid support in syslinux. This lets you take an ISO image, post-process it and then be able to either burn the ISO to a CD or write it to a USB stick with dd. Given that we stopped making a disk image form of boot.iso a couple of releases ago to save on duplicated/wasted space, this is obviously kind of cool.

The problem was that the first time I tested it, it looked like it overwrote the checksums we use for the mediacheck functionality in anaconda. It turns out I just wasn’t thinking — we need to implant the checksum *after* we do the isohybrid modification.

So without further ado, I’ve built a test version of the Fedora 11 boot.iso that is usable in this form. Testing of it would be much appreciated!

How to test

1. Download the test image
2. Try to burn it to a CD like you normally would. Ensure that it still boots normally. You don’t have to go through the full install, just boot it. Extra points if you can test mediacheck
3. Find a USB stick that’s at least 256 megs that doesn’t have any data you care about on it. Now try to write the test image to it using dd (dd if=test-isohybrid-boot.iso of=/path/to/device bs=1M). Again, you don’t have to install, just boot into the installer. Note that we won’t automatically find the second stage and you’ll get asked where to find the installer images.
4. Let me know the results in the comments (including type of machine).

Assuming this works, I’ll get the changes in so that we do this by default with boot.iso and then probably also try to make it so that the loader can automatically find the second stage image on either the CD or the USB stick. I’ll also consider doing similar for the livecds, although there’s more value with liveusb-creator / livecd-iso-to-disk there as you also want to set up persistence in a lot of cases.