Building native extensions.  This could take a while...
extconf.rb:1:in `require': no such file to load -- mkmf (LoadError)
        from extconf.rb:1

ERROR:  While executing gem ... (RuntimeError)
    ERROR: Failed to build gem native extension.
Gem files will remain installed in /var/lib/gems/1.8/gems/fastthread-0.6.4.1 for inspection.
  

Results logged to /var/lib/gems/1.8/gems/fastthread-0.6.4.1/ext/fastthread/gem_make.out
brahms:/home/nik#