到达本指南的第4步，即创建新的rails应用程序：
http://installfest.railsbridge.org/installfest/create_a_rails_app
收到以下输出，以及我的rails应用程序未创建：
create
/home/salpal/.rvm/rubies/ruby-2.2.4/lib/ruby/2.2.0/fileutils.rb:252:in `mkdir': Permission denied @ dir_s_mkdir - /home/salpal/railsbridge/test_app (Errno::EACCES)
from /home/salpal/.rvm/rubies/ruby-2.2.4/lib/ruby/2.2.0/fileutils.rb:252:in `fu_mkdir'
from /home/salpal/.rvm/rubies/ruby-2.2.4/lib/ruby/2.2.0/fileutils.rb:226:in `block (2 levels) in mkdir_p'
from /home/salpal/.rvm/rubies/ruby-2.2.4/lib/ruby/2.2.0/fileutils.rb:224:in `reverse_each'
from /home/salpal/.rvm/rubies/ruby-2.2.4/lib/ruby/2.2.0/fileutils.rb:224:in `block in mkdir_p'
from /home/salpal/.rvm/rubies/ruby-2.2.4/lib/ruby/2.2.0/fileutils.rb:210:in `each'
from /home/salpal/.rvm/rubies/ruby-2.2.4/lib/ruby/2.2.0/fileutils.rb:210:in `mkdir_p'
from /home/salpal/.rvm/gems/ruby-2.2.4/gems/thor-0.19.1/lib/thor/actions/empty_directory.rb:50:in `block in invoke!'
from /home/salpal/.rvm/gems/ruby-2.2.4/gems/thor-0.19.1/lib/thor/actions/empty_directory.rb:116:in `call'
from /home/salpal/.rvm/gems/ruby-2.2.4/gems/thor-0.19.1/lib/thor/actions/empty_directory.rb:116:in `invoke_with_conflict_check'
from /home/salpal/.rvm/gems/ruby-2.2.4/gems/thor-0.19.1/lib/thor/actions/empty_directory.rb:49:in `invoke!'
from /home/salpal/.rvm/gems/ruby-2.2.4/gems/thor-0.19.1/lib/thor/actions.rb:94:in `action'
from /home/salpal/.rvm/gems/ruby-2.2.4/gems/thor-0.19.1/lib/thor/actions/empty_directory.rb:14:in `empty_directory'
from /home/salpal/.rvm/gems/ruby-2.2.4/gems/railties-4.2.5/lib/rails/generators/app_base.rb:138:in `create_root'
from (eval):1:in `create_root'
from /home/salpal/.rvm/gems/ruby-2.2.4/gems/thor-0.19.1/lib/thor/command.rb:27:in `run'
from /home/salpal/.rvm/gems/ruby-2.2.4/gems/thor-0.19.1/lib/thor/invocation.rb:126:in `invoke_command'
from /home/salpal/.rvm/gems/ruby-2.2.4/gems/thor-0.19.1/lib/thor/invocation.rb:133:in `block in invoke_all'
from /home/salpal/.rvm/gems/ruby-2.2.4/gems/thor-0.19.1/lib/thor/invocation.rb:133:in `each'
from /home/salpal/.rvm/gems/ruby-2.2.4/gems/thor-0.19.1/lib/thor/invocation.rb:133:in `map'
from /home/salpal/.rvm/gems/ruby-2.2.4/gems/thor-0.19.1/lib/thor/invocation.rb:133:in `invoke_all'
from /home/salpal/.rvm/gems/ruby-2.2.4/gems/thor-0.19.1/lib/thor/group.rb:232:in `dispatch'
from /home/salpal/.rvm/gems/ruby-2.2.4/gems/thor-0.19.1/lib/thor/base.rb:440:in `start'
from /home/salpal/.rvm/gems/ruby-2.2.4/gems/railties-4.2.5/lib/rails/commands/application.rb:17:in `<top (required)>'
from /home/salpal/.rvm/rubies/ruby-2.2.4/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
from /home/salpal/.rvm/rubies/ruby-2.2.4/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
from /home/salpal/.rvm/gems/ruby-2.2.4/gems/railties-4.2.5/lib/rails/cli.rb:14:in `<top (required)>'
from /home/salpal/.rvm/rubies/ruby-2.2.4/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
from /home/salpal/.rvm/rubies/ruby-2.2.4/lib/ruby/site_ruby/2.2.0/rubygems/core_ext/kernel_require.rb:54:in `require'
from /home/salpal/.rvm/gems/ruby-2.2.4/gems/railties-4.2.5/bin/rails:9:in `<top (required)>'
from /home/salpal/.rvm/gems/ruby-2.2.4/bin/rails:23:in `load'
from /home/salpal/.rvm/gems/ruby-2.2.4/bin/rails:23:in `<main>'
from /home/salpal/.rvm/gems/ruby-2.2.4/bin/ruby_executable_hooks:15:in `eval'
from /home/salpal/.rvm/gems/ruby-2.2.4/bin/ruby_executable_hooks:15:in `<main>'
有谁知道这个的原因？任何帮助将不胜感激！