Install the package:

# apt-get install mysql2

Try to install the gem

$ gem install mysql2

If you're planning on using the mysql2 gem for your application then you'll want to install the libmysqlclient-dev package before you do that. Without it, you'll get an error when the gem tries to compile its native extensions:

Building native extensions.  This could take a while...

ERROR:  Error installing mysql2:

    ERROR: Failed to build gem native extension.

 

    /home/ryan/.rubies/ruby-2.2.0/bin/ruby extconf.rb

checking for ruby/thread.h... yes

checking for rb_thread_call_without_gvl() in ruby/thread.h... yes

checking for rb_thread_blocking_region()... yes

checking for rb_wait_for_single_fd()... yes

checking for rb_hash_dup()... yes

checking for rb_intern3()... yes

checking for mysql_query() in -lmysqlclient... no

checking for main() in -lm... yes

checking for mysql_query() in -lmysqlclient... no

checking for main() in -lz... yes

checking for mysql_query() in -lmysqlclient... no

checking for main() in -lsocket... no

checking for mysql_query() in -lmysqlclient... no

checking for main() in -lnsl... yes

checking for mysql_query() in -lmysqlclient... no

checking for main() in -lmygcc... no

checking for mysql_query() in -lmysqlclient... no

*** 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.

Install this package using:

$ sudo apt-get install libmysqlclient-dev

If you are running mysql and rake complains about not being able to find your mysql.sock file, you will need to add "socket: " to each of the database definitions