Ruby on Rails/Built-In Rails Tools/Convenient Rake tasks
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You can find out what tasks are currently available to Rake with the rake -T command. The tasks below are common and used on regular basis.
Database Tasks 
- rake db:migrate [VERSION=x]: Execute the migrations to the specified version. If the version is omitted then it will migrate to the highest version possible.
- rake db:sessions:clear: Clear all of the sessions in the database.
Test Tasks 
- rake test:units: Execute unit tests
Cache Tasks 
- rake tmp:cache:clear: Clear out the page/fragment cache.