<p>I am trying to install newgem on my linux box (sudo gem install newgem) and i am getting the following error:</p>

<pre><code>Building native extensions.  This could take a while...
ERROR:  Error installing newgem:
ERROR: Failed to build gem native extension.

/usr/bin/ruby1.8 extconf.rb install newgem
extconf.rb:1:in `require': no such file to load -- mkmf (LoadError)
from extconf.rb:1


Gem files will remain installed in /usr/lib/ruby/gems/1.8/gems/RedCloth-4.0.4 for inspection.
Results logged to /usr/lib/ruby/gems/1.8/gems/RedCloth-4.0.4/ext/redcloth_scan/gem_make.out
</code></pre>

<p>What could the problem be?</p>

```
mkmf
```
is a Ruby module which generates Makefiles.  It is supposed to be part of the standard Ruby install, but Debian (and derivatives) split it out into the
```
ruby1.8-dev
```
package.
If you can't find
```
mkmf.rb
```
in any of the directories outputted by
```
ruby -e'print $:.join("\n")'
```
, then you should figure out what you need to install.