compatibility. It may also pick up statically defined JSON user/group records from files in
<filename>/etc/userdb/</filename>, <filename>/run/userdb/</filename>,
<filename>/run/host/userdb/</filename> and <filename>/usr/lib/userdb/</filename> with the
- <literal>.user</literal> or <literal>.group</literal> extension.</para>
+ <literal>.user</literal> or <literal>.group</literal> extension. For more details about the extensions
+ read the <citerefentry><refentrytitle>nss-systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ manpage.</para>
<para>Most of <command>systemd-userdbd</command>'s functionality is accessible through the
<citerefentry><refentrytitle>userdbctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>