I am afraid that we don't have any tutorial/how-to-guide in order to do so.
Redmine 1.2.2 is a extremely old stack (it was released on 2011). Most of the components included in the Stack are very old. For example, according to the changelog, that version of the Redmine Stack is using MySQL 5.1.56, Ruby 1.8.7 or Rails 2.3.11. The current version ( 3.4.2) uses MySQL 5.6.37, Ruby 2.3.5 and Rails 4.2.8.
We highly recommend to our users to upgrade their stack to the latest published constantly for two reasons:
- Fix possible Security Issues.
- Guarantee Compatibility and include new features.
Honestly, I don't think it's possible to migrate between such different versions your stack. What would I do? I'd try to migrate from version 1.2.2 to the latest 1.X version. Check it at https://bitnami.com/stack/redmine/changelog.txt. Then migrate from the latest 1.X version to the first 2.X version. Then, migrate from the first 2.x version to the latest 2.X, etc. etc.
The migration/upgrading process is documented in the link below:
Please create a backup of everything before starting any migration process in order to ensure you don't lose anything.