diff options
| -rw-r--r-- | man/systemd-resolved.service.xml | 62 |
1 files changed, 60 insertions, 2 deletions
diff --git a/man/systemd-resolved.service.xml b/man/systemd-resolved.service.xml index 32512fd627..8f3494e36b 100644 --- a/man/systemd-resolved.service.xml +++ b/man/systemd-resolved.service.xml @@ -183,7 +183,9 @@ domain configured, in which case the query is sent to all of them in parallel).</para> <para>In case of single-label names, when search domains are defined, the same logic applies, except - that the name is first suffixed by each of the search domains in turn.</para></listitem> + that the name is first suffixed by each of the search domains in turn. Note that this search logic + doesn't apply to any names with at least one dot. Also see the discussion about compatiblity with + the traditional glibc resolver below.</para></listitem> <listitem><para>If a query does not match any configured routing domain (either per-link or global), it is sent to all DNS servers that are configured on links with the <varname>DefaultRoute=</varname> @@ -217,6 +219,63 @@ </refsect1> <refsect1> + <title>Compatibility with the traditional glibc stub resolver</title> + + <para>This section provides a short summary of differences in the stub resolver implemented by + <citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry> together + with <command>systemd-resolved</command> and the tranditional stub resolver implemented in + <citerefentry><refentrytitle>nss-dns</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para> + + <itemizedlist> + <listitem><para>Some names are always resolved internally (see Synthetic Records above). Traditionally + they would be resolved by <filename>nss-files</filename>, and only if provided in + <filename>/etc/hosts</filename>.</para></listitem> + + <listitem><para>Single-label names are not resolved for A and AAAA records using unicast DNS (unless + overriden with <varname>ResolveUnicastSingleLabel=</varname>, see + <citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>). + This is similar to the <option>no-tld-query</option> option being set in + <citerefentry><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>. + </para></listitem> + + <listitem><para>Search domains are not used for <emphasis>suffixing</emphasis> of multi-label names. + (Search domains are nevertheless used for lookup <emphasis>routing</emphasis>, for names that were + originally specified as single-label or multi-label.) Any name with at least one dot is always + interpreted as a FQDN. <filename>nss-dns</filename> would resolve names both as relative (using search + domains) and absolute FQDN names. Some names would be resolved as relative first, and after that query + has failed, as absolute, while other names would be resolved in opposite order. The + <varname>ndots</varname> option in <filename>/etc/resolv.conf</filename> was used to control how many + dots the name needs to have to be resolved as relative first. This stub resolver does not implement + this at all: multi-label names are only resolved as FQDNs. (There are currently more than 1500 + top-level domain names defined, and new ones are added regularly, often using "attractive" names that + are also likely to be used locally. Not looking up multi-label names in this fashion avoids fragility + in both directions: a valid global name could be obscured by a local name, and resolution of a relative + local name could suddenly break when a new top-level domain is created, or when a new subdomain of a + top-level domain in registered. Resolving any given name as either relative or absolute avoids this + ambiguity.)</para></listitem> + + <listitem><para>This resolver has a notion of the special <literal>.local</literal> domain used for + MulticastDNS, and will not route queries with that suffix to unicast DNS servers unless explicitly + configured, see above. Also, reverse lookups for link-local addresses are not sent to unicast DNS + servers.</para></listitem> + + <listitem><para>This resolver reads and caches <filename>/etc/hosts</filename> internally. (In other + words, <filename>nss-resolve</filename> replaces <filename>nss-files</filename> in addition to + <filename>nss-dns</filename>). Entries in <filename>/etc/hosts</filename> have highest priority.</para> + </listitem> + + <listitem><para>This resolver also implements LLMNR and MulticastDNS in addition to the classic unicast + DNS protocol, and will resolve single-label names using LLMNR (when enabled) and names ending in + <literal>.local</literal> using MulticastDNS (when enabled).</para></listitem> + + <listitem><para>Environment variables <varname>$LOCALDOMAIN</varname> and + <varname>$RES_OPTIONS</varname> described in + <citerefentry><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry> are not + supported currently.</para></listitem> + </itemizedlist> + </refsect1> + + <refsect1> <title><filename>/etc/resolv.conf</filename></title> <para>Four modes of handling <filename>/etc/resolv.conf</filename> (see @@ -302,7 +361,6 @@ synchronous way.</para></listitem> </varlistentry> </variablelist> - </refsect1> <refsect1> |