As a general rule, we strive to keep backwards compatibility between minor versions (e.g. 6.x to 6.y) so you can upgrade without any configuration file changes, but there are breaking changes between major versions (e.g. 5.x to 6.y). Migrating directly between non consecutive major versions (e.g. 1.x to 6.x) is not recommended.
You are looking at documentation for an older release. Not what you want? See the current release documentation.