<refsect1>
<title>Options</title>
- <para>The following options are available in the <literal>[Resolve]</literal> section:</para>
+ <para>The following options are available in the [Resolve] section:</para>
<variablelist class='network-directives'>
<varlistentry>
<term><varname>Domains=</varname></term>
- <listitem><para>A space-separated list of domains. These domains are used as search suffixes when resolving
- single-label hostnames (domain names which contain no dot), in order to qualify them into fully-qualified
- domain names (FQDNs). Search domains are strictly processed in the order they are specified, until the name
- with the suffix appended is found. For compatibility reasons, if this setting is not specified, the search
- domains listed in <filename>/etc/resolv.conf</filename> are used instead, if that file exists and any domains
- are configured in it. This setting defaults to the empty list.</para>
-
- <para>Specified domain names may optionally be prefixed with <literal>~</literal>. In this case they do not
- define a search path, but preferably direct DNS queries for the indicated domains to the DNS servers configured
- with the system <varname>DNS=</varname> setting (see above), in case additional, suitable per-link DNS servers
- are known. If no per-link DNS servers are known using the <literal>~</literal> syntax has no effect. Use the
- construct <literal>~.</literal> (which is composed of <literal>~</literal> to indicate a routing domain and
- <literal>.</literal> to indicate the DNS root domain that is the implied suffix of all DNS domains) to use the
- system DNS server defined with <varname>DNS=</varname> preferably for all domains.</para></listitem>
+ <listitem><para>A space-separated list of domains optionally prefixed with <literal>~</literal>,
+ used for two distinct purposes described below. Defaults to the empty list.</para>
+
+ <para>Any domains <emphasis>not</emphasis> prefixed with <literal>~</literal> are used as search
+ suffixes when resolving single-label hostnames (domain names which contain no dot), in order to
+ qualify them into fully-qualified domain names (FQDNs). These "search domains" are strictly processed
+ in the order they are specified in, until the name with the suffix appended is found. For
+ compatibility reasons, if this setting is not specified, the search domains listed in
+ <filename>/etc/resolv.conf</filename> with the <varname>search</varname> keyword are used instead, if
+ that file exists and any domains are configured in it.</para>
+
+ <para>The domains prefixed with <literal>~</literal> are called "routing domains". All domains listed
+ here (both search domains and routing domains after removing the <literal>~</literal> prefix) define
+ a search path that preferably directs DNS queries to this interface. This search path has an effect
+ only when suitable per-link DNS servers are known. Such servers may be defined through the
+ <varname>DNS=</varname> setting (see above) and dynamically at run time, for example from DHCP
+ leases. If no per-link DNS servers are known, routing domains have no effect.</para>
+
+ <para>Use the construct <literal>~.</literal> (which is composed from <literal>~</literal> to
+ indicate a routing domain and <literal>.</literal> to indicate the DNS root domain that is the
+ implied suffix of all DNS domains) to use the DNS servers defined for this link preferably for all
+ domains.</para></listitem>
</varlistentry>
<varlistentry>
<varlistentry>
<term><varname>ReadEtcHosts=</varname></term>
- <listitem><para>Takes a boolean argument. If <literal>yes</literal> (the default), the DNS stub resolver will read
- <filename>/etc/hosts</filename>, and try to resolve hosts or address by using the entries in the file before
- sending query to DNS servers.</para></listitem>
+ <listitem><para>Takes a boolean argument. If <literal>yes</literal> (the default),
+ <command>systemd-resolved</command> will read <filename>/etc/hosts</filename>, and try to resolve
+ hosts or address by using the entries in the file before sending query to DNS servers.
+ </para></listitem>
</varlistentry>
+ <varlistentry>
+ <term><varname>ResolveUnicastSingleLabel=</varname></term>
+ <listitem><para>Takes a boolean argument. When false (the default),
+ <command>systemd-resolved</command> will not resolve A and AAAA queries for single-label names over
+ classic DNS. Note that such names may still be resolved if search domains are specified (see
+ <varname>Domains=</varname> above), or using other mechanisms, in particular via LLMNR or from
+ <filename>/etc/hosts</filename>. When true, queries for single-label names will be forwarded to
+ global DNS servers even if no search domains are defined.
+ </para>
+
+ <para>This option is provided for compatibility with configurations where <emphasis>public DNS
+ servers are not used</emphasis>. Forwarding single-label names to servers not under your control is
+ not standard-conformant, see <ulink
+ url="https://www.iab.org/documents/correspondence-reports-documents/2013-2/iab-statement-dotless-domains-considered-harmful/">IAB
+ Statement</ulink>, and may create a privacy and security risk.</para></listitem>
+ </varlistentry>
</variablelist>
</refsect1>
projects / thirdparty / systemd.git / blobdiff