If you just installed Redmine and you get this error the first time you attempt to serve a web page:
Table 'redmine_development.settings' doesn't exist: SHOW FIELDS FROM `settings`
You forgot the essential but simple step of bootstrapping the database. Run:
rake db:migrate RAILS_ENV="production" rake redmine:load_default_data RAILS_ENV="production"
And maybe restart your server? That should fix it.