The main thing is not to panic and send the machine to boot as it may not boot up and create even bigger mess...
The solution to this is simple:
first kill of any instance of rpm and rpmq
do and rm -rf /var/lib/rpm/__db.*
and rpm --rebuilddb
You can test if it worked by doing apt-get update and if it works - it will complain about allot of installed packages having duplicates but thats not really a problem (if you crashed at the beginning).
In my case it left duplicates that are obsoleted with the new release so I had to do "apt-get -f install" to fix the immediate dependence problems before I can continue with the dist-upgrade.
some could be frightened by this message
You are about to do something potentially harmful
To continue type in the phrase 'Yes, do as I say!'
well it is the reality - it is potentially dangerous to remove them so it is wise the check if the packages that will be removed have duplicates installed already (hint - removing glibc* will trash your system if you don't have a new version installed).
If you think everything is fine, well guess again - the first thing you need to do is to install new apt with its deps, do an "apt-get update" and then "apt-get upgrade". Dist upgrade is not possible as it most likely there are broke deps and file conflicts at the system right now so most like it will fail at the the end.
In my case it was at around 800 packages so I have around 800 duplicates - ARRGH. Removing them manually is possibly the wisest thing as some packages do not contain fc6/fc7/fc8 tags so you don't have a reference point what package is newer. All so some Fedora 8 packages come without the fc8 tag, so go figure...
The dist upgrade part will be next after the system gets "fixed".
Here are few scripts that "can" help:
rpm -qa | grep fc7 > /tmp/fc7packages
rpm -qa | grep fc6 >> /tmp/fc7packages
for i in `cat /tmp/fc7packages | sort | sed -e "s/-[0-9].*//" `; do echo "$i check-------------------------------------------------------"; rpm -q $i; done > /tmp/checklist
This is not an fix for a beginner, but a guide on how I did it, so use it at your own risk!
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