Fedora 14 

“Fedora 14 (Laughlin)” is already running in my laptop. I have upgraded from v12 to v14.
The only issue was with the /boot disk space. In versions 13 and 14 the recomended /boot size is 500 Mb and in previous versions were 200 MB. If you want to upgrade your system and have the same problem within the /boot partition, follow the instructions:

  1. Create a file that takes up enough space that there is insufficient remaining disk space for preupgrade to download kernel and initrd.img. That means we need to fill up /boot. Here’s how to do that as root:

# dd if=/dev/zero of=/boot/preupgrade_filler bs=1M count=170

  1. Install the newest available version of image:Package-x-generic-16.pngpreupgrade.
  2. Run preupgrade from a command prompt or the Run Application dialog. Provide the requested password for root authorization.
  3. On the Choose desired release screen, enable unstable test releases.
  4. Choose Rawhide from the list of available upgrade targets, then click Apply.
  5. While downloading, preupgrade should warn that it failed to download installer data. Click quit for that.
  6. Next, change the amount of available disk space on the /boot partition by reducing the size of the /boot/preupgrade_filler file to 100MB. This should leave sufficient room for preupgrade to download the kernel and initrd.img but not enough room to download install.img. Once again, use the dd command:

# dd if=/dev/zero of=/boot/preupgrade_filler bs=1M count=100

  1. Re-run preupgrade. When prompted, click Yes to resume your upgrade.
  2. While downloading, preupgrade should warn that there wasn’t enough space to download install.img but it can be downloaded after reboot if you have a wired network connection. Click continue for that.
  3. When preupgrade is done don’t reboot immediately. Instead, remove the /boot/preupgrade_filler file and make sure your computer is connected to the network via an ethernet cable.

# rm /boot/preupgrade_filler

  1. Click reboot.

Laptop: DELL XPS M1330
Intel(R) Core(TM)2 Duo CPU T7300 @ 2.00 Ghz
2GB shared3 Dual Channel 667MHz DDR2 SDRAM
160GB configured with 7200 RPM SATA hard drive
128MB NVIDIA® GeForce® 8400M GS

Source: http://fedoraproject.org