You can control the location where are user are created by default
through UserManager config which is by default optional
<SecurityManager class="org.apache.jackrabbit.core.DefaultSecurityManager">
<!--
optional user manager configuration
-->
<UserManager
class="org.apache.jackrabbit.core.security.user.UserPerWorkspaceUserManager">
<param name="usersPath" value="/home/users"/>
<param name="groupsPath" value="/home/groups"/>
<param name="defaultDepth" value="1"/>
<param name="autoExpandTree" value="true"/>
<AuthorizableAction
class="org.apache.jackrabbit.core.security.user.action.AccessControlAction">
<param name="groupPrivilegeNames" value="jcr:read"/>
<param name="userPrivilegeNames" value="jcr:all"/>
</AuthorizableAction>
</UserManager>
<!--
optional workspace access manager configuration
-->
</SecurityManager>
Chetan Mehrotra