File MD5

Module helps to uniquely identify the files using their MD5 hashes.

All that this module does - extends the file_managed table with md5 column and, on file saving, set a value for it.

MD5 validation

Module provides an implementation of hook_file_validate() to validate file duplicates. This validation could be disabled here: admin/config/media/file-system.

Example implementation

• Create a form with submit callback.
• Save MD5 hash instead of file ID.
• Export configuration via Features.
• Add files to version control system.
• Reinstall the site and add files into database.

All these steps implemented in a test module: File MD5 (Test).

Note: likely, this module will not be understandable for newbies. Use it if you'd really know what to do.