rake在迁移数据库时中止

Question

在Arch机器上运行rake db:migrate时，会打印一个巨大的堆栈跟踪，然后耙取被中止。似乎并不存在真正的问题。关于双重定义的常量，所有行涉及警告。

[gilnaa@gilad-pc Hephaestus]$ rake db:migrate --trace | grep "error" 
Unsupported rails environment for compass 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/version.rb:2: warning: already initialized constant Rake::VERSION 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/version.rb:2: warning: previous definition of VERSION was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/version.rb:5: warning: already initialized constant Rake::Version::MAJOR 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/version.rb:5: warning: previous definition of MAJOR was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/version.rb:5: warning: already initialized constant Rake::Version::MINOR 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/version.rb:5: warning: previous definition of MINOR was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/version.rb:5: warning: already initialized constant Rake::Version::BUILD 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/version.rb:5: warning: previous definition of BUILD was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/version.rb:5: warning: already initialized constant Rake::Version::OTHER 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/version.rb:5: warning: previous definition of OTHER was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/version.rb:7: warning: already initialized constant Rake::Version::NUMBERS 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/version.rb:7: warning: previous definition of NUMBERS was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake.rb:27: warning: already initialized constant RAKEVERSION 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake.rb:27: warning: previous definition of RAKEVERSION was here 
WARNING: Possible conflict with Rake extension: String#ext already exists 
WARNING: Possible conflict with Rake extension: String#pathmap already exists 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/early_time.rb:17: warning: already initialized constant Rake::EARLY 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/early_time.rb:17: warning: previous definition of EARLY was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/alt_system.rb:32: warning: already initialized constant Rake::AltSystem::WINDOWS 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/alt_system.rb:32: warning: previous definition of WINDOWS was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/linked_list.rb:100: warning: already initialized constant Rake::LinkedList::EMPTY 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/linked_list.rb:100: warning: previous definition of EMPTY was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/scope.rb:40: warning: already initialized constant Rake::Scope::EMPTY 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/scope.rb:40: warning: previous definition of EMPTY was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/file_utils.rb:9: warning: already initialized constant FileUtils::RUBY 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/file_utils.rb:9: warning: previous definition of RUBY was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/file_utils.rb:88: warning: already initialized constant FileUtils::LN_SUPPORTED 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/file_utils.rb:88: warning: previous definition of LN_SUPPORTED was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/file_utils_ext.rb:16: warning: already initialized constant Rake::FileUtilsExt::DEFAULT 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/file_utils_ext.rb:16: warning: previous definition of DEFAULT was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/file_list.rb:44: warning: already initialized constant Rake::FileList::ARRAY_METHODS 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/file_list.rb:44: warning: previous definition of ARRAY_METHODS was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/file_list.rb:48: warning: already initialized constant Rake::FileList::MUST_DEFINE 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/file_list.rb:48: warning: previous definition of MUST_DEFINE was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/file_list.rb:52: warning: already initialized constant Rake::FileList::MUST_NOT_DEFINE 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/file_list.rb:52: warning: previous definition of MUST_NOT_DEFINE was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/file_list.rb:56: warning: already initialized constant Rake::FileList::SPECIAL_RETURN 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/file_list.rb:56: warning: previous definition of SPECIAL_RETURN was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/file_list.rb:62: warning: already initialized constant Rake::FileList::DELEGATING_METHODS 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/file_list.rb:62: warning: previous definition of DELEGATING_METHODS was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/file_list.rb:370: warning: already initialized constant Rake::FileList::DEFAULT_IGNORE_PATTERNS 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/file_list.rb:370: warning: previous definition of DEFAULT_IGNORE_PATTERNS was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/file_list.rb:376: warning: already initialized constant Rake::FileList::DEFAULT_IGNORE_PROCS 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/file_list.rb:376: warning: previous definition of DEFAULT_IGNORE_PROCS was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/promise.rb:11: warning: already initialized constant Rake::Promise::NOT_SET 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/promise.rb:11: warning: previous definition of NOT_SET was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/application.rb:13: warning: already initialized constant Rake::CommandLineOptionError 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/application.rb:13: warning: previous definition of CommandLineOptionError was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/application.rb:38: warning: already initialized constant Rake::Application::DEFAULT_RAKEFILES 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/application.rb:38: warning: previous definition of DEFAULT_RAKEFILES was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/application.rb:725: warning: already initialized constant Rake::Application::FIXNUM_MAX 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/application.rb:725: warning: previous definition of FIXNUM_MAX was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/task_arguments.rb:88: warning: already initialized constant Rake::EMPTY_TASK_ARGS 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/task_arguments.rb:88: warning: previous definition of EMPTY_TASK_ARGS was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/invocation_chain.rb:55: warning: already initialized constant Rake::InvocationChain::EMPTY 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/invocation_chain.rb:55: warning: previous definition of EMPTY was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/backtrace.rb:3: warning: already initialized constant Rake::Backtrace::SYS_KEYS 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/backtrace.rb:3: warning: previous definition of SYS_KEYS was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/backtrace.rb:4: warning: already initialized constant Rake::Backtrace::SYS_PATHS 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/backtrace.rb:4: warning: previous definition of SYS_PATHS was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/backtrace.rb:7: warning: already initialized constant Rake::Backtrace::SUPPRESSED_PATHS 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/backtrace.rb:7: warning: previous definition of SUPPRESSED_PATHS was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/backtrace.rb:11: warning: already initialized constant Rake::Backtrace::SUPPRESSED_PATHS_RE 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/backtrace.rb:11: warning: previous definition of SUPPRESSED_PATHS_RE was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/backtrace.rb:12: warning: already initialized constant Rake::Backtrace::SUPPRESS_PATTERN 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/backtrace.rb:12: warning: previous definition of SUPPRESS_PATTERN was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake.rb:72: warning: already initialized constant FileList 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake.rb:72: warning: previous definition of FileList was here 
/usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake.rb:73: warning: already initialized constant RakeFileUtils 
/home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake.rb:73: warning: previous definition of RakeFileUtils was here 
rake aborted! 
stack level too deep 
/usr/lib/ruby/gems/2.0.0/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:217 

Rails的版本是4.0.0 我怎样才能解决这个问题？

Answer 1

万一你没有达到它，这可能help.-

http://samuelanthony12.wordpress.com/2013/08/04/unsupported-rails-environment-for-compass-compass-rails/

Answer 2

通过拆卸和重新耙解决的问题。

Answer 3

其实，让我们来好好看看前两个警告信息（以便阅读线）： /usr/lib/ruby/gems/2.0.0/gems/rake-10.1.0/lib/rake/version.rb:2: warning: already initialized constant Rake::VERSION /home/gilnaa/.gem/ruby/2.0.0/gems/rake-10.1.0/lib/rake/version.rb:2: warning: previous definition of VERSION was here

正如你所看到的，耙被安装在两个/usr/lib/ruby/gems和/home/gilnaa/.gem/ruby/2.0.0/gems。其中之一显然太多了。正如你发现的，删除任何一个都会解决这个问题。您也可以尝试设置明确的GEM_PATH来选择适当的宝石集。

但是，最好的解决方案是使用bundler，并使用bundle exec rake db:migrate启动耙子。 Bundler竭尽全力使您的应用程序尽可能独立于其环境。