R – schema.rb not updating after transfer to a new machine

"rake db:migrate" will try and run all the outstanding migrations for your project. If you just want to dump the schema do a "rake db:schema:dump".
But I think you have a problem where it says that the table already exists. One of your migrations is failing because the table it is trying to add already exists in your db. Did you create one by hand? Did you down a migration, but not have a down written for it? You will need to fix this before you can write future migrations. If it is just a mistake, and the table is there and correct and you want to ignore this. My recommendation is to hack around it by commenting out the create table in the failing migration. Then run "rake db:migrate". Then but the create table back. This will update your schema version.
Make sure you write proper downs on all migrations.

When you use rails migrations, a table called schema_migrations is automatically created, which keeps track of what migrations have been applied, by storing the version number of each migration (this is the number that prefaces the migration name in the file name, ie db/migrate/_20090617111204__migration.rb). When you run rake db:migrate to migrate up, only migrations which have not been run previously (ie. their version is not contained in the table) will be run (for this reason, changing a migration that's already been executed will have no effect when running db:migrate). When migrating down, all versions found in schema_migrations that are greater than the version you are rolling back to will be undone.