Ruby on RailsでMySQLを使用する際に必要な作業手順

$ mysql -u root -p

mysql> CREATE USER 'railsuser'@'localhost' IDENTIFIED BY 'mypassword';

mysql> GRANT ALL PRIVILEGES ON *.* TO 'railsuser'@'localhost';

mysql> ERROR 1396 (HY000): Operation CREATE USER failed for 'railsuser'@'localhost'

mysql> SELECT USER FROM mysql.user; # ユーザ確認
mysql> DROP USER 'railsuser'@'localhost'; # ユーザrailsuserを削除

 # MySQL.  Versions 4.1 and 5.0 are recommended.
#
# Install the MYSQL driver
#   gem install mysql2
#
# Ensure the MySQL gem is defined in your Gemfile
#   gem 'mysql2'
#
# And be sure to use new-style password hashing:
#   https://dev.mysql.com/doc/refman/5.0/en/old-client.html
development:
  adapter: mysql2
  encoding: utf8
  database: Rails_development
  pool: 5
  username: railsuser
  password: mypassword
  socket: /var/run/mysqld/mysqld.sock

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
  adapter: mysql2
  encoding: utf8
  database: Rails_test
  pool: 5
  username: railsuser
  password: mypassword
  socket: /var/run/mysqld/mysqld.sock

production:
  adapter: mysql2
  encoding: utf8
  database: Rails_production
  pool: 5
  username: railsuser
  password: mypassword
  socket: /var/run/mysqld/mysqld.sock

$ bundle exec rake db:create #データベース作成

$ bundle exec rake db:create RAILS_ENV=production

$ bundle exec rake db:migrate # マイグレーション実行

$ bundle exec rake db:migrate RAILS_ENV=production

Mysql2::Error: Access denied for user 'railsuser'@'localhost' to database 'Rails_production': CREATE DATABASE

mysql> show grants for 'railsuser'@'localhost';
+-----------------------------------------------------------------------------------------------------------------+
| Grants for railsuser@localhost                                                                                            |
+-----------------------------------------------------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'railsuser'@'localhost' IDENTIFIED BY PASSWORD '***' |
+-----------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

Couldn’t create database for {“reconnect”=>false, “encoding”=>”utf8″, “username”=>***, “adapter”=>”mysql”, “database”=>”MyApp_production”, “host”=>”localhost”, “pool”=>5, “password”=>***, “socket”=>”/opt/local/var/run/mysql5/mysqld.sock”}, charset: utf8, collation: utf8_general_ci (if you set the charset manually, make sure you have a matching collation)

$ bundle exec rake db:create
  rake aborted!
  LoadError: cannot load such file -- readline
  /var/www/railsapp/config/application.rb:8:in `'
  /var/www/railsapp/Rakefile:4:in `require'
  /var/www/railsapp/Rakefile:4:in `'
  (See full trace by running task with --trace)

 gem 'rb-readline'

 $ gem install rb-readline

 gem 'mysql2'

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

/home/user/.rbenv/versions/2.0.0-p247/bin/ruby extconf.rb
checking for rb_thread_blocking_region()... yes
checking for rb_wait_for_single_fd()... 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.

Provided configuration options:
    --with-opt-dir

-- 途中省略 --

Gem files will remain installed in /home/user/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/mysql2-0.3.11 for inspection.
Results logged to /home/user/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/mysql2-0.3.11/ext/mysql2/gem_make.out

An error occurred while installing mysql2 (0.3.11), and Bundler cannot continue.
Make sure that `gem install mysql2 -v '0.3.11'` succeeds before bundling.

$ sudo apt-get install libmysqld-dev

Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 libmysqlclient-dev : Depends: libmysqlclient18 (= 5.6.20-1ubuntu14.04)
E: Unable to correct problems, you have held broken packages.

$ sudo dpkg --remove --force-depends libmysqlclient18
$ sudo apt-get install libmysqlclient18
$ sudo apt-get install libmysqlclient-dev