尝试安装gitlab
输入后：
sudo -u git -H bundle exec rake gitlab:setup RAILS_ENV=production
我收到了这个错误：
RAILS_ENV=production
rake aborted!
Please install the mysql2 adapter: `gem install activerecord-mysql2-adapter` (myis not part of the bundle. Add it to Gemfile.)
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/connection_adapters/mysql2_adapter.rb:3:in `<top (required)>'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/backports-3.3.2/lib/backports/tools.rb:328:in `require'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/backports-3.3.2/lib/backports/tools.rb:328:in `require_with_backports'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:251:in `block in require'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:236:in `load_dependency'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:251:in `require'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/connection_specification.rb:50:in `resolve_hash_connection'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/connection_specification.rb:41:in `resolve_string_connection'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/connection_specification.rb:25:in `spec'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/connection_specification.rb:130:in `establish_connection'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/railtie.rb:82:in `block (2 levels) in <class:Railtie>'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activesupport-3.2.13/lib/active_support/lazy_load_hooks.rb:36:in `instance_eval'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activesupport-3.2.13/lib/active_support/lazy_load_hooks.rb:36:in `execute_hook'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activesupport-3.2.13/lib/active_support/lazy_load_hooks.rb:26:in `block in on_load'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activesupport-3.2.13/lib/active_support/lazy_load_hooks.rb:25:in `each'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activesupport-3.2.13/lib/active_support/lazy_load_hooks.rb:25:in `on_load'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activerecord-3.2.13/lib/active_record/railtie.rb:74:in `block in <class:Railtie>'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/railties-3.2.13/lib/rails/initializable.rb:30:in `instance_exec'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/railties-3.2.13/lib/rails/initializable.rb:30:in `run'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/railties-3.2.13/lib/rails/initializable.rb:55:in `block in run_initializers'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/railties-3.2.13/lib/rails/initializable.rb:54:in `each'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/railties-3.2.13/lib/rails/initializable.rb:54:in `run_initializers'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/railties-3.2.13/lib/rails/application.rb:136:in `initialize!'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/railties-3.2.13/lib/rails/railtie/configurable.rb:30:in `method_missing'
/home/git/gitlab/config/environment.rb:5:in `<top (required)>'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/backports-3.3.2/lib/backports/tools.rb:328:in `require'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/backports-3.3.2/lib/backports/tools.rb:328:in `require_with_backports'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:251:in `block in require'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:236:in `load_dependency'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:251:in `require'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/railties-3.2.13/lib/rails/application.rb:103:in `require_environment!'
/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/railties-3.2.13/lib/rails/application.rb:297:in `block (2 levels) in initialize_tasks'
Tasks: TOP => gitlab:env:info => environment
(See full trace by running task with --trace)
内部gem列表：
activerecord-mysql2-adapter (0.0.3)
bigdecimal (1.2.0)
bundler (1.12.5)
charlock_holmes (0.6.9.4)
io-console (0.4.2)
json (1.7.7)
minitest (4.3.2)
modernizr-rails (2.6.2)
mysql2 (0.4.4)
psych (2.0.0)
rake (11.2.2, 0.9.6)
rdoc (4.0.0)
test-unit (2.0.0.0)
我尝试在config/database.yml中将适配器更改为MySQL2。