我想学习Ruby on Rails，并已经建立了一个测试环境。
我使用 "rails new Lab" 创建了一个新的Rails应用程序。
然后我在使用 "rake db::create" 命令创建数据库时遇到了问题：
henke@ubuntu:~/Rails Projects/Lab$ rake db::create --trace
(in /home/henke/Rails Projects/Lab)
rake aborted!
Don't know how to build task 'db::create'
/home/henke/.rvm/gems/ruby-1.9.2-p180/gems/rake-0.8.7/lib/rake.rb:1728:in `[]'
/home/henke/.rvm/gems/ruby-1.9.2-p180/gems/rake-0.8.7/lib/rake.rb:2050:in `invoke_task'
/home/henke/.rvm/gems/ruby-1.9.2-p180/gems/rake-0.8.7/lib/rake.rb:2029:in `block (2 levels) in top_level'
/home/henke/.rvm/gems/ruby-1.9.2-p180/gems/rake-0.8.7/lib/rake.rb:2029:in `each'
/home/henke/.rvm/gems/ruby-1.9.2-p180/gems/rake-0.8.7/lib/rake.rb:2029:in `block in top_level'
/home/henke/.rvm/gems/ruby-1.9.2-p180/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/home/henke/.rvm/gems/ruby-1.9.2-p180/gems/rake-0.8.7/lib/rake.rb:2023:in `top_level'
/home/henke/.rvm/gems/ruby-1.9.2-p180/gems/rake-0.8.7/lib/rake.rb:2001:in `block in run'
/home/henke/.rvm/gems/ruby-1.9.2-p180/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/home/henke/.rvm/gems/ruby-1.9.2-p180/gems/rake-0.8.7/lib/rake.rb:1998:in `run'
/home/henke/.rvm/gems/ruby-1.9.2-p180/gems/rake-0.8.7/bin/rake:31:in `<top (required)>'
/home/henke/.rvm/gems/ruby-1.9.2-p180/bin/rake:19:in `load'
/home/henke/.rvm/gems/ruby-1.9.2-p180/bin/rake:19:in `<main>'
我曾经尝试使用 "rake db::migrate"，但是出现了相同的错误。当我查看 "rake -T" 时，"db::create" 和 "db::migrate" 都在列表中。
我的环境:
- Ubuntu 10.10 - Ruby 1.9.2 (在我的主目录中使用 RVM) - Rails 3.0.5 - sqlite3-1.3.3
有什么想法吗？ 如果需要更多信息，请告诉我！