After upgrading via fedup to fc18, I noted with surprise that the NIC was renamed from eth0 to p17xx. Since I had se the system biosnames to return ethN on all single NIC desktops, I expected that to be carried forward in an upgrade. As you would expect all the inst scripts failed and the system never came up.
In case it's useful to someone else who is unhappy with upgrades breaking things they need not, here's my fix: # because every upgrade of Fedora changes the name of the damn default NIC, # get it from the system rather than using what you want. NIC=$(ip route | awk '/default/{print $5}')
And to get the IP on the NIC (I run DHCP to set the IP, reverse DNS to get the "real" machine name. # save the IP eth0IP=$(ifconfig ${NIC} | awk '/^ *inet /{print $2}' | sed 's/.*://')
Note that the IP determination works for old versions of ifconfig which return a different information format.
Hope this helps someone.