error about "gem install mysql -r "?

ruby 1.8.6 (2007-03-13 patchlevel 0) [i486-linux]
Rails 1.2.3

PlutoVik wrote:

ruby 1.8.6 (2007-03-13 patchlevel 0) [i486-linux]
Rails 1.2.3
debian:/home/ror# gem list -l
*** LOCAL GEMS ***
    Service layer for easy email delivery and testing.
actionpack (1.13.3)
    Web-flow and rendering framework putting the VC in MVC.
actionwebservice (1.2.3)
    Web service support for Action Pack.
activerecord (1.15.3)
    Implements the ActiveRecord pattern for ORM.
activesupport (1.4.2)
    Support and utility classes used by the Rails framework.
mysql (2.7.3)
    A win32-native build of the MySQL API module for Ruby.
rails (1.2.3)
    Web-application framework with template engine, control-flow
    and ORM.
rake (0.7.2)
    Ruby based make-like utility.
rubygems-update (0.9.2)
    RubyGems Update GEM
sources (0.0.1)
    This package provides download sources for remote gem installation

debian:/home/ror# gem install mysql -r
Select which gem to install for your platform (i486-linux)
1. mysql 2.7.3 (mswin32)
2. mysql 2.7.1 (mswin32)
3. mysql 2.7 (ruby)
4. mysql 2.6 (ruby)
5. Skip this gem
6. Cancel installation


Building native extensions. This could take a while...
ERROR: While executing gem ... (Gem::Installer::ExtensionBuildError)
    ERROR: Failed to build gem native extension.

ruby extconf.rb install mysql -r
`gem_original_require': no such file to load -- mkmf (LoadError)
        from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:
27:in `require'
        from extconf.rb:1

Gem files will remain installed in /usr/lib/ruby/gems/1.8/gems/
mysql-2.7 for inspection.
Results logged to /usr/lib/ruby/gems/1.8/gems/mysql-2.7/gem_make.out

any wrong?

sudo apt-get install ruby1.8-dev

Debian puts mkmf.rb into the ruby1.8-dev package even though it's part of the Ruby's standard library.