Just in case someone searches for this, here’s what happens on a fresh Ubuntu server when you try to deploy a project that needs imagemagick.

Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

/usr/local/bin/ruby extconf.rb

checking for Ruby version >= 1.8.5… yes

checking for gcc… yes

checking for Magick-config… no

Can’t install RMagick 2.13.1. Can’t find Magick-config in /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games

*** extconf.rb failed ***

Could not create Makefile due to some reason, probably lack of

necessary libraries and/or headers.  Check the mkmf.log file for more

details.  You may need configuration options.

Provided configuration options:

—with-opt-dir

—without-opt-dir

—with-opt-include

—without-opt-include=${opt-dir}/include

—with-opt-lib

—without-opt-lib=${opt-dir}/lib

—with-make-prog

—without-make-prog

—srcdir=.

—curdir

—ruby=/usr/local/bin/ruby

Gem files will remain installed in /home/railsuser/handygopher/shared/bundle/ruby/1.9.1/gems/rmagick-2.13.1 for inspection.

Results logged to /home/railsuser/handygopher/shared/bundle/ruby/1.9.1/gems/rmagick-2.13.1/ext/RMagick/gem_make.out

An error occured while installing rmagick (2.13.1), and Bundler cannot continue.

Make sure that `gem install rmagick -v ‘2.13.1’` succeeds before bundling.

Here’s what you need to install before trying to install the rmagick gem

sudo apt-get install libxml2-dev libxslt1-dev imagemagick libmagickwand-dev

There’s a convenient way to setup htop on OSX Lion if you’re using homebrew to manage software. 

First, make sure you’re up to date