Rails/redmine installation on debian etch as a user requires a bit of googling. This is what I have done.
First, as root, install these packages:
apt-get install rubygems -t etch-backports
aptitude install libopenssl-ruby1.8 libfcgi-ruby1.8
you need the backports version of gems as the version in etch is not compatible anymore with redmine.
Then you should follow these instructions: http://www.redmine.org/wiki/redmine/HowTo_Install_Redmine_in_a_home_directory_on_Debian