failed to remove local database when purging the package

First, purging the package fails because of the deamon thread he cannot kill.
After killing it manullay (sudo /etc/init.d/couchdb stop), he still doesn't remove everything from the computer since I still see my old database after reinstalling it.

To solve that, I had to go to the IRC channel (thanks to rnewson), he told me I had to kill remaining processes that lock the files.

I tried four commands: (I don't know which one worked)
killalll beam.smp
pkill beam.smp
killall beam
pkill beam

Then remove manually databases
sudo rm -R /var/lib/couchdb

Hope that helps.