I can't run "bundle update" because of "mysql2" gem

Question

I have this in the Gemfile:

gem 'mysql2'

But when I run bundle update, I get this error message:

An error occurred while installing mysql2 (0.3.16), and Bundler cannot continue.
Make sure that `gem install mysql2 -v '0.3.16'` succeeds before bundling.

I've tried to move this into the production section, like this:

group :production do
  gem 'mysql2'
end

But after running bundle update, the result is the same. This section is processed only in the production mode, or not?

How to get rid of this error message on localhost?

EDIT: The whole error message:

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

        /Users/radek/.rvm/rubies/ruby-1.9.3-p385/bin/ruby extconf.rb
checking for ruby/thread.h... *** 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
    --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=/Users/radek/.rvm/rubies/ruby-1.9.3-p385/bin/ruby
/Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:381:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
    from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:506:in `try_cpp'
    from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:931:in `block in have_header'
    from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:790:in `block in checking_for'
    from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:284:in `block (2 levels) in postpone'
    from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:254:in `open'
    from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:284:in `block in postpone'
    from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:254:in `open'
    from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:280:in `postpone'
    from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:789:in `checking_for'
    from /Users/radek/.rvm/rubies/ruby-1.9.3-p385/lib/ruby/1.9.1/mkmf.rb:930:in `have_header'
    from extconf.rb:9:in `<main>'


Gem files will remain installed in /Users/radek/.rvm/gems/ruby-1.9.3-p385/gems/mysql2-0.3.16 for inspection.
Results logged to /Users/radek/.rvm/gems/ruby-1.9.3-p385/gems/mysql2-0.3.16/ext/mysql2/gem_make.out
An error occurred while installing mysql2 (0.3.16), and Bundler cannot continue.
Make sure that `gem install mysql2 -v '0.3.16'` succeeds before bundling.

Thank you

Answer 1

On Ubuntu, run

sudo apt-get install libmysqlclient-dev

Or, if you use MariaDB, run

sudo apt-get install libmariadbclient-dev