What do I need to do to DataMapper to have a persistent sqlite database?

Try putting the full path in there (note there are 3 forward slashes):

DataMapper.setup(:default, "sqlite:///path/to/my/database/my.db")

Then you should see my.db under /path/to/my/database/

ruby sqlite orm sinatra datamapper

DataMapper.setup(:default, "sqlite3://#{Dir.pwd}/my.db")# your schemaDataMapper.finalizeDataMapper.auto_upgrade!

Also see docs.

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