Problem with Rake

I'm trying to install Redmine on a shared hosting. Here are some versions of software installed on it:

ruby 1.8.7 (2011-02-18 patchlevel 334) [x86_64-linux]

Rails 2.3.12

MySQL 5.0.91

Redmine - from current trunk (v1.2.1, I guess)

I'm using this guide for installation: http://www.redmine.org/projects/redmine/wiki/RedmineInstall. All the steps before this I completed successfully. Installation fails while running "rake generate_session_store". What can be wrong? Here is the most part of the errors I get after running this command:

NOTE: Gem::SourceIndex#add_spec is deprecated, use
Specification.add_spec. It will be removed on or afte开发者_运维百科r 2011-11-01.
Gem::SourceIndex#add_spec called from
/usr/lib/ruby/site_ruby/1.8/rubygems/source_index.rb:127. 
... repeated a lot of times

From the page you mention:

Ruby 1.9 is not supported yet. You have to use Ruby 1.8.x as stated above. RubyGems 1.3.7 or higher is required with following limitations : Rails 2.3.5 will fail with RubyGems 1.5.0 or later, stick to previous versions of RubyGems ! Rails 2.3.11 will fail with RubyGems 1.7.0 or later, stick to previous versions of RubyGems ! Rake 0.8.7 is required (rake 0.9.x is not supported by Rails yet)

You should downgrade your rubygems installation.

Next question: How do you downgrade rubygems?

Update

I answer here to your last comment. If you can't install any software as root, but you have a normal user account on your machine (I assume so since you can run commands), you can solve your issue by installing RVM. With that you can have a local ruby environment installed in your home directory and you can control all these aspects: gem version, ruby version, installed gems and so on. Once installed to downgrade rubygems itself refer to my previous link.

If you do not have an user account, well you can't solve this issue...