If you are having trouble to install the mysql2 gem, try the following:

# apt-get install build-essential ruby-dev libmysqlclient-dev

If you're having troubles with LOAD DATA INFILE ("Errcode 13"):

• copy the CSV file to the DB folder (/var/lib/mysql/DATABASE), and
• use the filename only, not the full path.

If you're having troubles with LOAD DATA LOCAL INFILE ("The used command is not allowed with this MySQL version"):

• temporary solution: mysql -uUSER -p --local-infile DATABASE
• permanent solution: sudo nano /etc/mysql/my.cnf and insert local-infile under [mysql]; save the file, close the editor and type sudo service mysql restart.

Note: LOAD DATA LOCAL INFILE uses IGNORE. If you want to know why some records were skipped, you must use LOAD DATA INFILE (without LOCAL). (Reference)