Confluence 6 uses its own user management

In some specific cases, you may wish to disable Confluence's built-in user management or use an external user directory for user management entirely. For example Jira software or Jira Service Desk. You can disable Confluence's internal user management in Confluence's External User Management . You need to have system user administrative privileges to do this.

You might disable Confluence's internal user management:

• When using Crowd's directory permissions to manage your users, Confluence cannot update the Crowd directory (you will get a system error message when Confluence tries to write data to Crowd). Please see the Connecting to Crowd or Jira for User Management page for more information.
• If you are using the Jira application to manage users, then the admin center for all users is in the Jira application. Please see the Connecting to Crowd or Jira for User Management page for more information.

To disable users and user management in Confluence:

1.  >  General Configuration >  Security Configuration .
2. Click Edit .
3. Select the External user management selection dialog and click Save to make your configuration effective.

Note: If you have External :

• You will not be able to add users and user groups in Confluence.
• You will not be able to edit user information (full username and email address) in Confluence's internal directory in Confluence.
• You will not be able to allow users to automatically register with your site.
• Forgot Password connections will not appear in the Confluence login page.
• Users cannot reset their passwords in Confluence themselves.

https://www.cwiki.us/display/CONFLUENCEWIKI/Disabling+the+Built-In+User+Management