specified user and group must have been created statically in the user database no later than the moment the
service is started, for example using the
<citerefentry><refentrytitle>sysusers.d</refentrytitle><manvolnum>5</manvolnum></citerefentry> facility, which
- is applied at boot or package install time.</para></listitem>
+ is applied at boot or package install time.</para>
+
+ <para>If the <varname>User=</varname> setting is used the supplementary group list is initialized
+ from the specified user's default group list, as defined in the system's user and group
+ database. Additional groups may be configured through the <varname>SupplementaryGroups=</varname>
+ setting (see below).</para></listitem>
</varlistentry>
<varlistentry>