On Fri, Jul 05, 2013 at 02:07:28PM +0800, Qi.Chen@windriver.com wrote:
> From: Chen Qi <Qi.Chen@windriver.com>
> 
> We may want to add a user or group which does not logically belong to
> any specific package. For example, we may want to add a user with the
> name 'tester' to our image. Besides, we may want to delete or modify
> user/group in our image.
> 
> This patch adds a variable, USER_GROUP_SETTINGS, which is dedicated
> to these tasks. The configuration format is detailed in the local.conf.
> sample.extended file.
> 
> This patch also adds a function, set_user_group, which happens at
> the end of the ROOTFS_POSTPROCESS_COMMAND. It handles the settings
> in the USER_GROUP_SETTINGS variable.

Why not use extra package just with user?

See "[PATCH v3 0/5] Allow xuser to shutdown (cover letter only)"