You can install gem ruby-debug, but the rails server cannot find it

Question

I found a rather interesting problem when installing ruby ​​stones

bluehat@Matapan:~/code/Amacron$ rails server --debugger
=> Booting WEBrick
=> Rails 3.0.3 application starting in development on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
You need to install ruby-debug to run the server in debugging mode. With gems, use 'gem install ruby-debug'
Exiting
bluehat@Matapan:~/code/Amacron$ sudo gem install ruby-debug
Successfully installed ruby-debug-0.10.4
1 gem installed
Installing ri documentation for ruby-debug-0.10.4...
Installing RDoc documentation for ruby-debug-0.10.4...
bluehat@Matapan:~/code/Amacron$ rails server --debugger
=> Booting WEBrick
=> Rails 3.0.3 application starting in development on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
You need to install ruby-debug to run the server in debugging mode. With gems, use 'gem install ruby-debug'
Exiting
bluehat@Matapan:~/code/Amacron$ sudo gem update ruby-debug
Updating installed gems
Nothing to update
bluehat@Matapan:~/code/Amacron$ gem --version
1.3.7
bluehat@Matapan:~/code/Amacron$ rails --version
Rails 3.0.3

System is Modern Ubuntu 11.04

Answer 1

Have you put this stone in your gemfile app?

Answer 2

I solved this problem by installing the irb package. The error message was near ruby-debug, but as soon as I installed debian packaged for irb, everything was fine.

Answer 3

. , Gemfile "gem" ruby-debug ". , .

Answer 4

. script/server sudo, , , , .