The update from one Fedora version to the next by yum was never officially supported – however, given that you were brave enough it could work out. However, for the next Fedora version you shouldn’t try it because you might even make your system unbootable!
Dave Jones posted that the new kernel’s driver system for hard disks can cause serious problems if you make a normal yum update from an old kernel to a new kernel. There are actually two reasons which, combined, cause that danger: Fedora changed the way drivers are build into the kernel:
The reason for this is twofold. Firstly, we switched over to the new libata PATA drivers, so all the drivers changed names.
This normally wouldn’t be a big deal if it wasn’t for a second change. We used to build every single IDE driver into the vmlinuz, and let runtime probing do the right thing. This is somewhat wasteful, so we’ve moved to building them as modules.
So, when you fire up yum you have a problem:
Your FC6 kernel that you’re running when you do ‘yum update’ is going to be running the old IDE drivers built into the kernel. So your /etc/modprobe.conf will have no knowledge of the new libata PATA drivers. So when the %post of the kernel rpm installation calls mkinitrd, and it creates an initrd based upon your existing modprobe.conf, you’ll end up with one with no drivers for your hard disk controller.
You can work around if you know how to use mkinitrd, but the easiest way is to run the normal installation DVD and run the upgrade option. So, be careful when Fedora 7 hits the streets!
Update
The Yum Update FAQ at the fedoraporject wiki has been updated. There you find more detailed information plus information how to perform an update nevertheless. Thanks Totally Lost for the hint.
