specify user id when creating user in keycloak

Question

I'm investigating a migration process from a legacy system into keycloak. Based on some of the ideas here: https://github.com/Smartling/keycloak-user-migration-provider we're looking to create user accounts in keycloak at the point of login by looking up user credentials from some dedicated endpoints on our legacy system.

As part of this, I need the user ID to remain the same as it was in the legacy system.

Is it possible to create a user with a specified ID rather than relying on keycloak to auto-generate it?

Answer 1

Running into this issue when attempting to create users via the API, I looked into the code for the users service. It looks like it is currently not possible to set the user id due to how the user is created.

From the code in https://github.com/keycloak/keycloak/blob/master/services/src/main/java/org/keycloak/services/resources/admin/UsersResource.java specifically on line https://github.com/keycloak/keycloak/blob/7cfe6addf01676939206e034a87c791460031032/services/src/main/java/org/keycloak/services/resources/admin/UsersResource.java#L115 the user is first created using the username, then updated. I believe id is not an updatable field. Thus it is not currently possible.

Answer 2

Checking the api I see it is now possible to add an optional "id" field in the userRepresentation object that you pass to create a new user in keycloak.

Find more information here: https://www.keycloak.org/docs-api/5.0/rest-api/index.html#_userrepresentation