我是Rails的新手。我关注Rails网上的教程。安装sqlite3后，我尝试启动服务器，但不能。终端向我展示此代码
invitado@Home:~/blog$ bin/rails server
=> Booting Puma
=> Rails 5.2.2 application starting in development
=> Run `rails server -h` for more startup options
/usr/lib/ruby/vendor_ruby/rack/mime.rb:54: warning: already initialized constant Rack::Mime::MIME_TYPES
/var/lib/gems/2.3.0/gems/rack-2.0.6/lib/rack/mime.rb:49: warning: previous definition of MIME_TYPES was here
/usr/lib/ruby/vendor_ruby/rack/file.rb:15: warning: already initialized constant Rack::File::ALLOWED_VERBS
/var/lib/gems/2.3.0/gems/rack-2.0.6/lib/rack/file.rb:17: warning: previous definition of ALLOWED_VERBS was here
/usr/lib/ruby/vendor_ruby/rack/file.rb:16: warning: already initialized constant Rack::File::ALLOW_HEADER
/var/lib/gems/2.3.0/gems/rack-2.0.6/lib/rack/file.rb:18: warning: previous definition of ALLOW_HEADER was here
/usr/lib/ruby/vendor_ruby/rack/response.rb:23: warning: already initialized constant Rack::Response::CHUNKED
/var/lib/gems/2.3.0/gems/rack-2.0.6/lib/rack/response.rb:26: warning: previous definition of CHUNKED was here
Exiting
/var/lib/gems/2.3.0/gems/bootsnap-1.4.1/lib/bootsnap/load_path_cache/core_ext/active_support.rb:76:in `block in load_missing_constant': uninitialized constant Rack::Session::Abstract::Persisted (NameError)
from /var/lib/gems/2.3.0/gems/bootsnap-1.4.1/lib/bootsnap/load_path_cache/core_ext/active_support.rb:8:in without_bootsnap_cache
等等。如果有人能帮助我，我很感激。谢谢！
一个更好的选择是安装RVM或RBENV，以处理应用程序的Ruby/Gems版本。只需按照此链接http://railsapps.github.io/installrubyonrails-ubuntu.html我认为这会帮助您。：）