Fedora 12 has been out of the oven since about Nov 17 so it's high time I upgrade before it spoils.  As with the previous release, I look forward to any new features in KDE 4.3.  (As you recall from the previous upgrades, KDE was introduced rewritten almost entirely in Qt4).  Also noteworthy to mention is the issues in ATI graphics that popped up after upgrading.  Hopefully the community has had time to catch up as at the time support for my old Radeon 9600 was dropped and after some searches at the time not even ATI was maintaining support for Linux drivers for the family of chipsets of the cards.  Unfortunately, there was even some division around how cards like Radeon are supported from Linus himself.  (As far as I'm concerned David can do what he wants  just like Linus did  ).
See the previous upgrade from Fedora 10 and Fedora 11 on some of the more recent issues then so you can decide further if using the default supplied Radeon drivers is enough or if you prefer to stay with the current version or wait for F13.  Fedora 12 has some kernel improvements in versions 2.6.30+ that I would like to take advantage off as well since upgrading to F11, fglrx no longer supported my card and I couldn't scrape enough time to tinker around with the Xorg default graphics and their 3D support (And so my Tux Racer didn't work.  🙁 much to the disappointment of my kids. )  'ATI R600/R700 3D and KMS support and other graphic improvements' have been added to this version to, hopefully, resolve some of my woes:

QUICK STEPS

1. nice -n 19 yum update (If you get No Packages marked for Update you are good.)
2. cd /some/dir
3. mkdir ./F11toF12
4. cd ./F11toF12
5. Ensure you have debuglevel=10 and errorlevel=10 enabled in /etc/yum.conf in case we need more debugging information.
6. nice -n 19 yum -y upgrade (should be the same as step 1 above)
7. nice -n 19 yum clean all
8. nice -n 19 yum clean all (Just to make sure everything looks clean)
9.  wget http://download.fedora.redhat.com/pub/fedora/linux/releases/12/Fedora/i386/os/Packages/fedora-release-12-1.noarch.rpm
10. wget http://download.fedora.redhat.com/pub/fedora/linux/releases/12/Fedora/i386/os/Packages/fedora-release-notes-12.0.0-4.fc12.noarch.rpm 
11. rpm -Uvh fedora-release*.rpm
12. cat /etc/fedora-release  (Make sure ‘Fedora release 12 (Constantine)‘ appears )
13. nice -n 19 yum -y upgrade 2>&1|tee -a ./F11-to-F12-upgrade.Dec.31.2009.10.00.AM.txt
14. Refer below for any issues and repeat from step 12) as necessary.

 

RUNNING INTO PROBLEMS

The problems are generally similar throughout the upgrades.  Most issues can be resolved by removing the conflicting package as I did in this case, once I decided that I can reinstall the package after the upgrade anyway:

# cat /etc/*fedora-release*
Fedora release 11 (Leonidas)
# rpm -Uvh fedora-release*.rpm
warning: fedora-release-12-1.noarch.rpm: Header V3 RSA/SHA256 signature: NOKEY, key ID 57bbccba
error: Failed dependencies:
        indexhtml is needed by (installed) lynx-2.8.6-20.fc11.i586
You have new mail in /var/spool/mail/root
# rpm -e lynx-2.8.6-20.fc11.i586
# rpm -Uvh fedora-release*.rpm
warning: fedora-release-12-1.noarch.rpm: Header V3 RSA/SHA256 signature: NOKEY, key ID 57bbccba
Preparing…                ########################################### [100%]
   1:fedora-release         ########################################### [ 50%]
   2:fedora-release-notes   ########################################### [100%]
# cat /etc/fedora-release
Fedora release 12 (Constantine)
#

As in previous upgrades, some RPM packages don't make the cut or have not yet been redied for the latest release.  So a short list of package errors ensued after trying to upgrade through step 13:

Error: Missing Dependency: lohit-fonts-bengali is needed by package fonts-bengali-2.1.5-3.fc8.noarch (installed)
Error: Missing Dependency: libkrb4.so.2 is needed by package krbafs-utils-1.2.2-10.1.i386 (installed)
Error: Missing Dependency: libkrb4.so.2(krb4_2_MIT) is needed by package krbafs-1.2.2-10.1.i386 (installed)
Error: Missing Dependency: lohit-fonts-hindi is needed by package fonts-hindi-2.1.5-3.fc8.noarch (installed)
Error: Missing Dependency: libdes425.so.3(des425_3_MIT) is needed by package krbafs-utils-1.2.2-10.1.i386 (installed)
Error: Missing Dependency: libkrb4.so.2 is needed by package krbafs-1.2.2-10.1.i386 (installed)
Error: Missing Dependency: lohit-fonts-gujarati is needed by package fonts-gujarati-2.1.5-3.fc8.noarch (installed)
Error: Missing Dependency: lohit-fonts-punjabi is needed by package fonts-punjabi-2.1.5-3.fc8.noarch (installed)
Error: Missing Dependency: libcrypto.so.8 is needed by package VirtualBox-OSE-3.0.10-1.fc11.i586 (installed)
Error: Missing Dependency: libkrb4.so.2(krb4_2_MIT) is needed by package krbafs-utils-1.2.2-10.1.i386 (installed)
Error: Missing Dependency: libssl.so.8 is needed by package gpac-libs-0.4.5-7.fc11.i586 (installed)
Error: Missing Dependency: libdes425.so.3 is needed by package krbafs-utils-1.2.2-10.1.i386 (installed)
Error: Missing Dependency: libcrypto.so.8 is needed by package gpac-libs-0.4.5-7.fc11.i586 (installed)
Error: Missing Dependency: lohit-fonts-tamil is needed by package fonts-tamil-2.1.5-3.fc8.noarch (installed)
 

For this one I simply went over the packages on the right side and removed them.  (Again, if a package is really needed, you would need to judge whether removal is appropriate for you.)  I used rpm -e <PACKAGE NAME> to remove the package.  Rerunning the upgrade produced this:

 Error: Missing Dependency: lohit-fonts-punjabi is needed by package fonts-punjabi-2.1.5-3.fc8.noarch (installed)

Removing the installed package, allowed me to upgrade to pass that point and continue further.  Following the above, the upgrade completed flawlessly (minus some custom RPM's I had installed earlier) .  Best of all, my graphics were again restored though tweaking them, I'll leave for another topic. 

Cheers!
TK