Last updated 2 years ago by Tobias McNultydjango
The Django documentation recommends always starting your project with a custom user model (even if it's identical to Django's to begin with), to make it easier to customize later if you need to. But what are you supposed to do if you didn't see this when starting a project, or if you inherited a project without a custom user model and you need to add one?
At Caktus, when Django first added support for a custom user model, we were still using South for migrations. Hard to believe! Nearly six years ago, I wrote a post about migrating to a custom user model that is, of course, largely obsolete now that Django has built-in support for database migrations. As such, I thought it would be helpful to put together a new post for anyone who needs to add a custom user model to their existing project on Django 2.0+.
As of the time of this post, ticket #25313 is open in the Django ticket tracker for adding further documentation about this issue. This ticket includes some high-level steps to follow when moving to a custom user model, and I recommend familiarizing yourself with this first. As noted in the documentation under Changing to a custom user model mid-project, "Changing AUTHUSERMODEL after you’ve created database tables is significantly more difficult since it affects foreign keys and many-to-many relationships, for example."
The instructions I put together below vary somewhat from the high-level instructions in ticket #25313, I think (hope) in positive and less destructive ways. That said, there's a reason this ticket has been open for more than four years — it’s hard. So, as mentioned in the ticket:
Proceed with caution, and make sure you have a database backup (and a working process for restoring it) before changing your production database.