Redmine

I just installed redmine via apt-get on Linux Mint 14. Before I added the repository from https://launchpad.net/~ondrej/+archive/redmine. Everything works fine.

Environment:

Redmine version 2.3.1.stable
    Ruby version 1.8.7 (x86_64-linux)
    Rails version 3.2.13

Next step would be for me to install a few plugins. I followed the instructions on http://www.redmine.org/projects/redmine/wiki/Plugins.

The plugin to install http://www.redmine.org/plugins/redmine-projects-accordion

I created a directory /plugins under /usr/share/redmine (this is where also the app-folder is).
Next step to do a rake redmine:plugins:migrate RAILS_ENV=production. Now im getting a little Warning: WARNING: 'require 'rake/rdoctask'' is deprecated.
Next step is to restart apache(using passenger-mod) to restart redmine. But there is no plugin on my administration.

As Im not a ruby/rails dev I can only guess where to search. Any ideas where to look for further information etc? Would be thankful for any advice.

Thanks a lot in advance.