source: vendor/current/docs-xml/smbdotconf/winbind/idmapconfig.xml

<samba:parameter name="idmap config DOMAIN : OPTION"
                 context="G"
                 type="string"
                 xmlns:samba="http://www.samba.org/samba/DTD/samba-doc">
<description>

        <para>
        ID mapping in Samba is the mapping between Windows SIDs and Unix user
        and group IDs. This is performed by Winbindd with a configurable plugin
        interface. Samba's ID mapping is configured by options starting with the
        <smbconfoption name="idmap config"/> prefix.
        An idmap option consists of the <smbconfoption name="idmap config"/>
        prefix, followed by a domain name or the asterisk character (*),
        a colon, and the name of an idmap setting for the chosen domain.
        </para>

        <para>
        The idmap configuration is hence divided into groups, one group
        for each domain to be configured, and one group with the
        asterisk instead of a proper domain name, which specifies the
        default configuration that is used to catch all domains that do
        not have an explicit idmap configuration of their own.
        </para>

        <para>
        There are three general options available:
        </para>

        <variablelist>
                <varlistentry>
                <term>backend = backend_name</term>
                <listitem><para>
                This specifies the name of the idmap plugin to use as the
                SID/uid/gid backend for this domain. The standard backends are
                tdb
                (<citerefentry><refentrytitle>idmap_tdb</refentrytitle> <manvolnum>8</manvolnum> </citerefentry>),
                tdb2
                (<citerefentry><refentrytitle>idmap_tdb2</refentrytitle> <manvolnum>8</manvolnum></citerefentry>),
                ldap
                (<citerefentry><refentrytitle>idmap_ldap</refentrytitle> <manvolnum>8</manvolnum></citerefentry>),
                rid
                (<citerefentry><refentrytitle>idmap_rid</refentrytitle> <manvolnum>8</manvolnum></citerefentry>),
                hash
                (<citerefentry><refentrytitle>idmap_hash</refentrytitle> <manvolnum>8</manvolnum></citerefentry>),
                autorid
                (<citerefentry><refentrytitle>idmap_autorid</refentrytitle> <manvolnum>8</manvolnum></citerefentry>),
                ad
                (<citerefentry><refentrytitle>idmap_ad</refentrytitle> <manvolnum>8</manvolnum></citerefentry>)
                and nss
                (<citerefentry><refentrytitle>idmap_nss</refentrytitle> <manvolnum>8</manvolnum></citerefentry>).
                The corresponding manual pages contain the details, but
                here is a summary.
                </para>
                <para>
                The first three of these create mappings of their own using
                internal unixid counters and store the mappings in a database.
                These are suitable for use in the default idmap configuration.
                The rid and hash backends use a pure algorithmic calculation
                to determine the unixid for a SID. The autorid module is a
                mixture of the tdb and rid backend. It creates ranges for
                each domain encountered and then uses the rid algorithm for each
                of these automatically configured domains individually.
                The ad backend uses unix ids stored in Active Directory via
                the standard schema extensions. The nss backend reverses
                the standard winbindd setup and gets the unix ids via names
                from nsswitch which can be useful in an ldap setup.
                </para></listitem>
                </varlistentry>

                <varlistentry>
                <term>range = low - high</term>
                <listitem><para>
                Defines the available matching uid and gid range for which the
                backend is authoritative. For allocating backends, this also
                defines the start and the end of the range for allocating
                new unique IDs.
                </para>
                <para>
                winbind uses this parameter to find the backend that is
                authoritative for a unix ID to SID mapping, so it must be set
                for each individually configured domain and for the default
                configuration. The configured ranges must be mutually disjoint.
                </para></listitem>
                </varlistentry>

                <varlistentry>
                <term>read only = yes|no</term>
                <listitem><para>
                This option can be used to turn the writing backends
                tdb, tdb2, and ldap into read only mode. This can be useful
                e.g. in cases where a pre-filled database exists that should
                not be extended automatically.
                </para></listitem>
                </varlistentry>
        </variablelist>

        <para>
        The following example illustrates how to configure the <citerefentry>
        <refentrytitle>idmap_ad</refentrytitle> <manvolnum>8</manvolnum>
        </citerefentry> backend for the CORP domain and the
        <citerefentry><refentrytitle>idmap_tdb</refentrytitle>
        <manvolnum>8</manvolnum></citerefentry> backend for all other
        domains. This configuration assumes that the admin of CORP assigns
        unix ids below 1000000 via the SFU extensions, and winbind is supposed
        to use the next million entries for its own mappings from trusted
        domains and for local groups for example.
        </para>

        <programlisting>
        idmap config * : backend = tdb
        idmap config * : range = 1000000-1999999

        idmap config CORP : backend  = ad
        idmap config CORP : range = 1000-999999
        </programlisting>
        
</description>
</samba:parameter>