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systemd/man/resolved.conf.xml

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man: drop mode line in file headers This is already included in .dir-locals, so we don't need it in the files themselves.
2018-07-03 05:15:39 +08:00
<?xml version='1.0'?>
man: use same header for all files The "include" files had type "book" for some raeason. I don't think this is meaningful. Let's just use the same everywhere. $ perl -i -0pe 's^..DOCTYPE (book|refentry) PUBLIC "-//OASIS//DTD DocBook XML V4.[25]//EN"\s+"http^<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"\n "http^gms' man/*.xml
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
man: use same version in public and system ident.
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
man: correctly document default for DNSSEC= and DNSoverTLS= https://bugzilla.redhat.com/show_bug.cgi?id=1926323
2021-12-19 00:03:43 +08:00
<!ENTITY % entities SYSTEM "custom-entities.ent" >
%entities;
]>
license: LGPL-2.1+ -> LGPL-2.1-or-later
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
resolved: add daemon to manage resolv.conf Also remove the equivalent functionality from networkd.
2014-05-19 04:10:48 +08:00
build-sys: s/ENABLE_RESOLVED/ENABLE_RESOLVE/ The configuration option was called -Dresolve, but the internal define was …RESOLVED. This options governs more than just resolved itself, so let's settle on the version without "d".
2017-10-03 19:12:29 +08:00
<refentry id="resolved.conf" conditional='ENABLE_RESOLVE'
Reindent man pages to 2ch
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xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>resolved.conf</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>resolved.conf</refentrytitle>
<manvolnum>5</manvolnum>
</refmeta>
<refnamediv>
<refname>resolved.conf</refname>
<refname>resolved.conf.d</refname>
<refpurpose>Network Name Resolution configuration files</refpurpose>
</refnamediv>
<refsynopsisdiv>
man: use <simplelist> for file lists in synopsis With <para><filename>…</filename></para>, we get a separate "paragraph" for each line, i.e. entries separated by empty lines. This uses up a lot of space and was only done because docbook makes it hard to insert a newline. In some other places, <literallayout> was used, but then we cannot indent the source text (because the whitespace would end up in the final page). We can get the desired result with <simplelist>. With <simplelist> the items are indented in roff output, but not in html output. In some places this looks better then no indentation, and in others it would probably be better to have no indent. But this is a minor issue and we cannot control that. (I didn't convert all spots. There's a bunch of other man pages which have two lines, e.g. an executable and service file, and it doesn't matter there so much.)
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<para><simplelist>
<member><filename>/etc/systemd/resolved.conf</filename></member>
man: document all the new paths
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<member><filename>/run/systemd/resolved.conf</filename></member>
man: document /usr/local/lib in search paths
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<member><filename>/usr/local/lib/systemd/resolved.conf</filename></member>
man: document all the new paths
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<member><filename>/usr/lib/systemd/resolved.conf</filename></member>
man: use <simplelist> for file lists in synopsis With <para><filename>…</filename></para>, we get a separate "paragraph" for each line, i.e. entries separated by empty lines. This uses up a lot of space and was only done because docbook makes it hard to insert a newline. In some other places, <literallayout> was used, but then we cannot indent the source text (because the whitespace would end up in the final page). We can get the desired result with <simplelist>. With <simplelist> the items are indented in roff output, but not in html output. In some places this looks better then no indentation, and in others it would probably be better to have no indent. But this is a minor issue and we cannot control that. (I didn't convert all spots. There's a bunch of other man pages which have two lines, e.g. an executable and service file, and it doesn't matter there so much.)
2023-12-14 19:52:03 +08:00
<member><filename>/etc/systemd/resolved.conf.d/*.conf</filename></member>
<member><filename>/run/systemd/resolved.conf.d/*.conf</filename></member>
man: document /usr/local/lib in search paths
2024-06-05 23:08:57 +08:00
<member><filename>/usr/local/lib/systemd/resolved.conf.d/*.conf</filename></member>
man: use <simplelist> for file lists in synopsis With <para><filename>…</filename></para>, we get a separate "paragraph" for each line, i.e. entries separated by empty lines. This uses up a lot of space and was only done because docbook makes it hard to insert a newline. In some other places, <literallayout> was used, but then we cannot indent the source text (because the whitespace would end up in the final page). We can get the desired result with <simplelist>. With <simplelist> the items are indented in roff output, but not in html output. In some places this looks better then no indentation, and in others it would probably be better to have no indent. But this is a minor issue and we cannot control that. (I didn't convert all spots. There's a bunch of other man pages which have two lines, e.g. an executable and service file, and it doesn't matter there so much.)
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<member><filename>/usr/lib/systemd/resolved.conf.d/*.conf</filename></member>
</simplelist></para>
Reindent man pages to 2ch
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</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>These configuration files control local DNS and LLMNR
doc: correct orthography, word forms and missing/extraneous words
2014-08-03 13:11:37 +08:00
name resolution.</para>
Reindent man pages to 2ch
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</refsect1>
Do not advertise .d snippets over main config file For daemons which have a main configuration file, there's little reason for the administrator to use configuration snippets. They are useful for packagers which need to override settings, but we shouldn't advertise that as the main way of configuring those services. https://bugs.freedesktop.org/show_bug.cgi?id=89397
2015-03-04 08:10:21 +08:00
<xi:include href="standard-conf.xml" xpointer="main-conf" />
Reindent man pages to 2ch
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<refsect1>
<title>Options</title>
tree-wide: drop quotes from around [section] For users, the square brackets already serve as markup and clearly delineate the section name from surrounding text. Putting additional markup around that only adds clutter. Also, we were very inconsistent in using the quotes. Let's just drop them altogether.
2020-07-06 17:00:06 +08:00
<para>The following options are available in the [Resolve] section:</para>
man: actually say which section resolv.conf's setting should be placed in
2016-01-29 21:46:06 +08:00
Reindent man pages to 2ch
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<variablelist class='network-directives'>
<varlistentry>
<term><varname>DNS=</varname></term>
man: update explanation about the format to specify DNS servers
2020-07-19 12:57:51 +08:00
<listitem><para>A space-separated list of IPv4 and IPv6 addresses to use as system DNS servers. Each address can
optionally take a port number separated with <literal>:</literal>, a network interface name or index separated with
<literal>%</literal>, and a Server Name Indication (SNI) separated with <literal>#</literal>. When IPv6 address is
specified with a port number, then the address must be in the square brackets. That is, the acceptable full formats
are <literal>111.222.333.444:9953%ifname#example.com</literal> for IPv4 and
<literal>[1111:2222::3333]:9953%ifname#example.com</literal> for IPv6. DNS requests are sent to one of the listed
DNS servers in parallel to suitable per-link DNS servers acquired from
resolved: allow configuration of routing domains in Domains=
2016-01-26 06:40:02 +08:00
<citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> or
set at runtime by external applications. For compatibility reasons, if this setting is not specified, the DNS
servers listed in <filename>/etc/resolv.conf</filename> are used instead, if that file exists and any servers
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
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are configured in it. This setting defaults to the empty list.</para>
<xi:include href="version-info.xml" xpointer="v213"/></listitem>
Reindent man pages to 2ch
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</varlistentry>
<varlistentry>
<term><varname>FallbackDNS=</varname></term>
man: update explanation about the format to specify DNS servers
2020-07-19 12:57:51 +08:00
<listitem><para>A space-separated list of IPv4 and IPv6 addresses to use as the fallback DNS servers. Please see
man: fix typo in resolved.conf
2020-09-06 01:57:00 +08:00
<varname>DNS=</varname> for acceptable format of addresses. Any per-link DNS servers obtained from
Reindent man pages to 2ch
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<citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
resolved: allow configuration of routing domains in Domains=
2016-01-26 06:40:02 +08:00
take precedence over this setting, as do any servers set via <varname>DNS=</varname> above or
<filename>/etc/resolv.conf</filename>. This setting is hence only used if no other DNS server information is
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
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known. If this option is not given, a compiled-in list of DNS servers is used instead.</para>
<xi:include href="version-info.xml" xpointer="v216"/></listitem>
Reindent man pages to 2ch
2015-02-04 10:14:13 +08:00
</varlistentry>
resolved: add a generic DnsSearchDomain concept With this change, we add a new object to resolved, "DnsSearchDomain=" which wraps a search domain. This is then used to introduce a global search domain list, in addition to the existing per-link search domain list which is reword to make use of this new object too. This is preparation for implement proper unicast DNS search domain support.
2015-11-25 04:12:51 +08:00
<varlistentry>
<term><varname>Domains=</varname></term>
man: explain route-only domains a bit more The details discussion of how search and route-only domains work is in systemd-resolved.service(8). But users are more likely to look at resolved.conf(5), because that's where Domains= is described. So let's add a reference to the other man page there, and also strengthen the text a bit. In particular, in systemd-resolved.service(8) we say "route-only", which makes the distinction with search domains clearer. Let's use the same in the other man page too. This is based on feedback from Lukáš Nykrýn that the man page is not clear enough.
2023-03-07 20:48:09 +08:00
<listitem><para>A space-separated list of domains, optionally prefixed with <literal>~</literal>,
man: rework description of Domains= We said that ~domains "do not define a search path", which is mighty confusing, because this is exactly what they do. So let's try to make this a bit easier for the reader: start by saying that there are two things going on here, and describe each one from user's POV.
2020-06-03 00:21:04 +08:00
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>
man: explain route-only domains a bit more The details discussion of how search and route-only domains work is in systemd-resolved.service(8). But users are more likely to look at resolved.conf(5), because that's where Domains= is described. So let's add a reference to the other man page there, and also strengthen the text a bit. In particular, in systemd-resolved.service(8) we say "route-only", which makes the distinction with search domains clearer. Let's use the same in the other man page too. This is based on feedback from Lukáš Nykrýn that the man page is not clear enough.
2023-03-07 20:48:09 +08:00
<para>The domains prefixed with <literal>~</literal> are called "route-only domains". All domains
listed here (<emphasis>both search domains and route-only domains</emphasis> 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, route-only domains have no
effect.</para>
man: rework description of Domains= We said that ~domains "do not define a search path", which is mighty confusing, because this is exactly what they do. So let's try to make this a bit easier for the reader: start by saying that there are two things going on here, and describe each one from user's POV.
2020-06-03 00:21:04 +08:00
<para>Use the construct <literal>~.</literal> (which is composed from <literal>~</literal> to
man: explain route-only domains a bit more The details discussion of how search and route-only domains work is in systemd-resolved.service(8). But users are more likely to look at resolved.conf(5), because that's where Domains= is described. So let's add a reference to the other man page there, and also strengthen the text a bit. In particular, in systemd-resolved.service(8) we say "route-only", which makes the distinction with search domains clearer. Let's use the same in the other man page too. This is based on feedback from Lukáš Nykrýn that the man page is not clear enough.
2023-03-07 20:48:09 +08:00
indicate a route-only domain and <literal>.</literal> to indicate the DNS root domain that is the
man: rework description of Domains= We said that ~domains "do not define a search path", which is mighty confusing, because this is exactly what they do. So let's try to make this a bit easier for the reader: start by saying that there are two things going on here, and describe each one from user's POV.
2020-06-03 00:21:04 +08:00
implied suffix of all DNS domains) to use the DNS servers defined for this link preferably for all
man: explain route-only domains a bit more The details discussion of how search and route-only domains work is in systemd-resolved.service(8). But users are more likely to look at resolved.conf(5), because that's where Domains= is described. So let's add a reference to the other man page there, and also strengthen the text a bit. In particular, in systemd-resolved.service(8) we say "route-only", which makes the distinction with search domains clearer. Let's use the same in the other man page too. This is based on feedback from Lukáš Nykrýn that the man page is not clear enough.
2023-03-07 20:48:09 +08:00
domains.</para>
<para>See "Protocols and Routing" in
<citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for details of how search and route-only domains are used.</para>
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
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man: document that Domains=local bind the domain to unicast DNS, not mDNS Fixes: #28983
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<para>Note that configuring the MulticastDNS domain <literal>local</literal> as search or routing
domain has the effect of routing lookups for this domain to classic unicast DNS. This may be used to
provide compatibility with legacy installations that use this domain in a unicast DNS context,
against the IANA assignment of this domain to pure MulticastDNS purposes. Search and routing domains
are a unicast DNS concept, they <emphasis>cannot</emphasis> be used to resolve single-label lookups
via MulticastDNS.</para>
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
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<xi:include href="version-info.xml" xpointer="v229"/>
man: explain route-only domains a bit more The details discussion of how search and route-only domains work is in systemd-resolved.service(8). But users are more likely to look at resolved.conf(5), because that's where Domains= is described. So let's add a reference to the other man page there, and also strengthen the text a bit. In particular, in systemd-resolved.service(8) we say "route-only", which makes the distinction with search domains clearer. Let's use the same in the other man page too. This is based on feedback from Lukáš Nykrýn that the man page is not clear enough.
2023-03-07 20:48:09 +08:00
</listitem>
resolved: add a generic DnsSearchDomain concept With this change, we add a new object to resolved, "DnsSearchDomain=" which wraps a search domain. This is then used to introduce a global search domain list, in addition to the existing per-link search domain list which is reword to make use of this new object too. This is preparation for implement proper unicast DNS search domain support.
2015-11-25 04:12:51 +08:00
</varlistentry>
Reindent man pages to 2ch
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<varlistentry>
<term><varname>LLMNR=</varname></term>
<listitem><para>Takes a boolean argument or
<literal>resolve</literal>. Controls Link-Local Multicast Name
Resolution support (<ulink
man: fix RFC ref in resolved.conf man page (#9976) This is a simple one-character fix to reference the correct RFC for LLMNR, which is RFC 4795, not RFC 4794.
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url="https://tools.ietf.org/html/rfc4795">RFC 4795</ulink>) on
doc: correct punctuation and improve typography in documentation
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the local host. If true, enables full LLMNR responder and
doc: correct orthography, word forms and missing/extraneous words
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resolver support. If false, disables both. If set to
<literal>resolve</literal>, only resolution support is enabled,
Reindent man pages to 2ch
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but responding is disabled. Note that
<citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
resolved: allow configuration of routing domains in Domains=
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also maintains per-link LLMNR settings. LLMNR will be
enabled on a link only if the per-link and the
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
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global setting is on.</para>
<xi:include href="version-info.xml" xpointer="v216"/></listitem>
Reindent man pages to 2ch
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</varlistentry>
resolved: add global config option to control mDNS stack
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<varlistentry>
<term><varname>MulticastDNS=</varname></term>
<listitem><para>Takes a boolean argument or
<literal>resolve</literal>. Controls Multicast DNS support (<ulink
url="https://tools.ietf.org/html/rfc6762">RFC 6762</ulink>) on
the local host. If true, enables full Multicast DNS responder and
resolver support. If false, disables both. If set to
<literal>resolve</literal>, only resolution support is enabled,
but responding is disabled. Note that
<citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
also maintains per-link Multicast DNS settings. Multicast DNS will be
enabled on a link only if the per-link and the
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
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global setting is on.</para>
<xi:include href="version-info.xml" xpointer="v234"/></listitem>
resolved: add global config option to control mDNS stack
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</varlistentry>
man: add basic documentation for resolved.conf's DNSSEC= switch
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<varlistentry>
<term><varname>DNSSEC=</varname></term>
man: clarify DNSSEC= again https://github.com/systemd/systemd/pull/28407#issuecomment-1640900239
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<listitem><para>Takes a boolean argument or <literal>allow-downgrade</literal>.</para>
<para>If set to true, all DNS lookups are DNSSEC-validated locally (excluding LLMNR and Multicast
DNS). If the response to a lookup request is detected to be invalid a lookup failure is returned to
applications. Note that this mode requires a DNS server that supports DNSSEC. If the DNS server does
not properly support DNSSEC all validations will fail.</para>
<para>If set to <literal>allow-downgrade</literal>, DNSSEC validation is attempted, but if the server
does not support DNSSEC properly, DNSSEC mode is automatically disabled. Note that this mode makes
DNSSEC validation vulnerable to "downgrade" attacks, where an attacker might be able to trigger a
downgrade to non-DNSSEC mode by synthesizing a DNS response that suggests DNSSEC was not
supported.</para>
man/resolve: update DNSSEC description This behavior was changed. Fixes: 9c47b334445a ("resolved: enable DNS proxy mode if client wants DNSSEC")
2024-03-07 09:08:00 +08:00
<para>If set to false, DNS lookups are not DNSSEC validated.</para>
man: clarify DNSSEC= again https://github.com/systemd/systemd/pull/28407#issuecomment-1640900239
2023-07-19 20:16:15 +08:00
<para>Note that DNSSEC validation requires retrieval of additional DNS data, and thus results in a
small DNS lookup time penalty.</para>
man: add basic documentation for resolved.conf's DNSSEC= switch
2016-01-05 07:31:32 +08:00
<para>DNSSEC requires knowledge of "trust anchors" to prove
data integrity. The trust anchor for the Internet root domain
man: add documentation for dnssec-trust-anchors.d(5)
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is built into the resolver, additional trust anchors may be
defined with
<citerefentry><refentrytitle>dnssec-trust-anchors.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
man: reword sentence
2016-01-29 07:24:27 +08:00
Trust anchors may change at regular intervals, and old trust
man: add documentation for dnssec-trust-anchors.d(5)
2016-01-05 21:20:27 +08:00
anchors may be revoked. In such a case DNSSEC validation is
not possible until new trust anchors are configured locally or
the resolver software package is updated with the new root
trust anchor. In effect, when the built-in trust anchor is
revoked and <varname>DNSSEC=</varname> is true, all further
lookups will fail, as it cannot be proved anymore whether
lookups are correctly signed, or validly unsigned. If
man: add basic documentation for resolved.conf's DNSSEC= switch
2016-01-05 07:31:32 +08:00
<varname>DNSSEC=</varname> is set to
resolved: rename "downgrade-ok" mode to "allow-downgrade" After discussing this with Tom, we figured out "allow-downgrade" sounds nicer.
2016-01-06 00:44:16 +08:00
<literal>allow-downgrade</literal> the resolver will
man: fix a few typos
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automatically turn off DNSSEC validation in such a case.</para>
man: add basic documentation for resolved.conf's DNSSEC= switch
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<para>Client programs looking up DNS data will be informed
whether lookups could be verified using DNSSEC, or whether the
returned data could not be verified (either because the data
was found unsigned in the DNS, or the DNS server did not
support DNSSEC or no appropriate trust anchors were known). In
the latter case it is assumed that client programs employ a
secondary scheme to validate the returned DNS data, should
this be required.</para>
<para>It is recommended to set <varname>DNSSEC=</varname> to
man: fix a few typos
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true on systems where it is known that the DNS server supports
man: add basic documentation for resolved.conf's DNSSEC= switch
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DNSSEC correctly, and where software or trust anchor updates
happen regularly. On other systems it is recommended to set
<varname>DNSSEC=</varname> to
resolved: rename "downgrade-ok" mode to "allow-downgrade" After discussing this with Tom, we figured out "allow-downgrade" sounds nicer.
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<literal>allow-downgrade</literal>.</para>
resolved,networkd: add a per-interface DNSSEC setting This adds a DNSSEC= setting to .network files, and makes resolved honour them.
2016-01-06 02:57:33 +08:00
<para>In addition to this global DNSSEC setting
<citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
resolved: allow configuration of routing domains in Domains=
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also maintains per-link DNSSEC settings. For system DNS
resolved,networkd: add a per-interface DNSSEC setting This adds a DNSSEC= setting to .network files, and makes resolved honour them.
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servers (see above), only the global DNSSEC setting is in
resolved: allow configuration of routing domains in Domains=
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effect. For per-link DNS servers the per-link
resolved,networkd: add a per-interface DNSSEC setting This adds a DNSSEC= setting to .network files, and makes resolved honour them.
2016-01-06 02:57:33 +08:00
setting is in effect, unless it is unset in which case the
global setting is used instead.</para>
resolved: try to detect fritz.box-style private DNS zones, and downgrade to non-DNSSEC mode for them This adds logic to detect cases like the Fritz!Box routers which serve a private DNS domain "fritz.box" under the TLD "box" that does not exist in the root servers. If this is detected DNSSEC validation is turned off for this private domain, thus improving compatibility with such private DNS zones. This should be fairly secure as we first rely on the proof that .box does not exist before this logic is applied. Nevertheless the logic is only enabled for DNSSEC=allow-downgrade mode. This logic does not work for routers that set up a full DNS zone directly under a non-existing TLD, as in that case we cannot prove that the domain is truly non-existing according to the root servers.
2016-01-06 05:13:56 +08:00
<para>Site-private DNS zones generally conflict with DNSSEC
operation, unless a negative (if the private zone is not
signed) or positive (if the private zone is signed) trust
anchor is configured for them. If
<literal>allow-downgrade</literal> mode is selected, it is
attempted to detect site-private DNS zones using top-level
domains (TLDs) that are not known by the DNS root server. This
logic does not work in all private zone setups.</para>
man: correctly document default for DNSSEC= and DNSoverTLS= https://bugzilla.redhat.com/show_bug.cgi?id=1926323
2021-12-19 00:03:43 +08:00
<para>Defaults to <literal>&DEFAULT_DNSSEC_MODE;</literal>.</para>
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
2023-08-23 00:52:36 +08:00
<xi:include href="version-info.xml" xpointer="v229"/>
man: add basic documentation for resolved.conf's DNSSEC= switch
2016-01-05 07:31:32 +08:00
</listitem>
</varlistentry>
man: document DNS-over-TLS options
2018-06-12 03:33:57 +08:00
<varlistentry>
resolve: rename PrivateDNS to DNSOverTLS PrivateDNS is not considered a good name for this option, so rename it to DNSOverTLS
2018-06-14 02:26:24 +08:00
<term><varname>DNSOverTLS=</varname></term>
man: document DNS-over-TLS options
2018-06-12 03:33:57 +08:00
<listitem>
systemd-resolved: use hostname for certificate validation in DoT Widely accepted certificates for IP addresses are expensive and only affordable for larger organizations. Therefore if the user provides the hostname in the DNS= option, we should use it instead of the IP address.
2020-03-04 07:31:25 +08:00
<para>Takes a boolean argument or <literal>opportunistic</literal>. If
true all connections to the server will be encrypted. Note that this
mode requires a DNS server that supports DNS-over-TLS and has a valid
certificate. If the hostname was specified in <varname>DNS=</varname>
man: remove unintentionally repetitive words
2021-11-11 17:01:19 +08:00
by using the format <literal>address#server_name</literal> it
systemd-resolved: use hostname for certificate validation in DoT Widely accepted certificates for IP addresses are expensive and only affordable for larger organizations. Therefore if the user provides the hostname in the DNS= option, we should use it instead of the IP address.
2020-03-04 07:31:25 +08:00
is used to validate its certificate and also to enable Server Name
Indication (SNI) when opening a TLS connection. Otherwise
the certificate is checked against the server's IP.
If the DNS server does not support DNS-over-TLS all DNS requests will fail.</para>
<para>When set to <literal>opportunistic</literal>
man: document DNS-over-TLS options
2018-06-12 03:33:57 +08:00
DNS request are attempted to send encrypted with DNS-over-TLS.
If the DNS server does not support TLS, DNS-over-TLS is disabled.
Note that this mode makes DNS-over-TLS vulnerable to "downgrade"
attacks, where an attacker might be able to trigger a downgrade
to non-encrypted mode by synthesizing a response that suggests
DNS-over-TLS was not supported. If set to false, DNS lookups
are send over UDP.</para>
<para>Note that DNS-over-TLS requires additional data to be
send for setting up an encrypted connection, and thus results
in a small DNS look-up time penalty.</para>
Be more specific in resolved.conf man page with regard to DNSOverTLS DNSOverTLS in strict mode (value yes) does check the server, as it is said in the first few lines of the option documentation. The check is not performed in "opportunistic" mode, however, as that is allowed by RFC 7858, section "4.1. Opportunistic Privacy Profile". > With such a discovered DNS server, the client might or might not validate the > resolver. These choices maximize availability and performance, but they leave > the client vulnerable to on-path attacks that remove privacy.
2019-11-14 00:37:15 +08:00
<para>Note that in <literal>opportunistic</literal> mode the
resolver is not capable of authenticating the server, so it is
vulnerable to "man-in-the-middle" attacks.</para>
man: document DNS-over-TLS options
2018-06-12 03:33:57 +08:00
man: suffix settings name with = and enclose in <varname>
2020-11-18 20:47:43 +08:00
<para>In addition to this global <varname>DNSOverTLS=</varname> setting
man: document DNS-over-TLS options
2018-06-12 03:33:57 +08:00
<citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
man: suffix settings name with = and enclose in <varname>
2020-11-18 20:47:43 +08:00
also maintains per-link <varname>DNSOverTLS=</varname> settings. For system DNS servers (see above), only the global
<varname>DNSOverTLS=</varname> setting is in effect. For per-link DNS servers the per-link setting is in effect, unless
it is unset in which case the global setting is used instead.</para>
man: document DNS-over-TLS options
2018-06-12 03:33:57 +08:00
man: correctly document default for DNSSEC= and DNSoverTLS= https://bugzilla.redhat.com/show_bug.cgi?id=1926323
2021-12-19 00:03:43 +08:00
<para>Defaults to <literal>&DEFAULT_DNS_OVER_TLS_MODE;</literal>.</para>
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
2023-08-23 00:52:36 +08:00
<xi:include href="version-info.xml" xpointer="v239"/>
man: document DNS-over-TLS options
2018-06-12 03:33:57 +08:00
</listitem>
</varlistentry>
resolved: add option to disable caching (#3592) In some cases, caching DNS results locally is not desirable, a it makes DNS cache poisoning attacks a tad easier and also allows users on the system to determine whether or not a particular domain got visited by another user. Thus provide a new "Cache" resolved.conf option to disable it.
2016-06-24 13:54:28 +08:00
<varlistentry>
<term><varname>Cache=</varname></term>
man: fix formatting in resolved.conf(5)
2020-04-16 01:52:47 +08:00
<listitem><para>Takes a boolean or <literal>no-negative</literal> as argument. If
<literal>yes</literal> (the default), resolving a domain name which already got queried earlier will
return the previous result as long as it is still valid, and thus does not result in a new network
request. Be aware that turning off caching comes at a performance penalty, which is particularly high
when DNSSEC is used. If <literal>no-negative</literal>, only positive answers are cached.</para>
man: rework resolved.conf's Cache= documentation Let's not mention the supposed security benefit of turning off caching. It is really questionnable, and I#d rather not create the impression that we actually believed turning off caching would be a good idea. Instead, mention that Cache=no is implicit if a DNS server on the local host is used.
2016-07-23 02:17:23 +08:00
resolved: allow cache responses from local DNS servers
2020-11-24 21:44:07 +08:00
<para>Note that caching is turned off by default for host-local DNS servers.
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
2023-08-23 00:52:36 +08:00
See <varname>CacheFromLocalhost=</varname> for details.</para>
<xi:include href="version-info.xml" xpointer="v231"/></listitem>
resolved: allow cache responses from local DNS servers
2020-11-24 21:44:07 +08:00
</varlistentry>
<varlistentry>
<term><varname>CacheFromLocalhost=</varname></term>
<listitem><para>Takes a boolean as argument. If <literal>no</literal> (the default), and response cames from
host-local IP address (such as 127.0.0.1 or ::1), the result wouldn't be cached in order to avoid
potential duplicate local caching.</para>
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
2023-08-23 00:52:36 +08:00
<xi:include href="version-info.xml" xpointer="v248"/>
resolved: allow cache responses from local DNS servers
2020-11-24 21:44:07 +08:00
</listitem>
resolved: add option to disable caching (#3592) In some cases, caching DNS results locally is not desirable, a it makes DNS cache poisoning attacks a tad easier and also allows users on the system to determine whether or not a particular domain got visited by another user. Thus provide a new "Cache" resolved.conf option to disable it.
2016-06-24 13:54:28 +08:00
</varlistentry>
resolved: add an option to control the DNS stub listener
2016-09-01 06:34:29 +08:00
<varlistentry>
<term><varname>DNSStubListener=</varname></term>
resolved: add "proxy-only" stub on 127.0.0.54 This beefs up the DNS stub logic to listen on two IP addresses: 127.0.0.53 (as before) + 127.0.0.54 (new). When the latter is contact our stub will operate in "bypass" mode only, i.e we'll try to pass DNS requests as unmodified upstream as we can (and not do mDNS/LLMNR and such, also no DNSSEC validation – but we'll still do DNS-over-TLS wrapping). This is supposed to be useful for container environments or tethering: this stub could be exposed (via NAT redirect) to clients of this system and we'll try to stay out of the way with doing too much DNS magic ourselves, but still expose whatever the current DNS server is from upstream under a stable address/port. How to use this: # iptables -t nat -I PREROUTING -p udp -i <interface> --dport 53 -j DNAT --to 127.0.0.54:53 # echo 1 > /proc/sys/net/ipv4/conf/<interface>/route_localnet
2021-11-22 19:20:05 +08:00
<listitem><para>Takes a boolean argument or one of <literal>udp</literal> and
<literal>tcp</literal>. If <literal>udp</literal>, a DNS stub resolver will listen for UDP requests
on addresses 127.0.0.53 and 127.0.0.54, port 53. If <literal>tcp</literal>, the stub will listen for
TCP requests on the same addresses and port. If <literal>yes</literal> (the default), the stub listens
for both UDP and TCP requests. If <literal>no</literal>, the stub listener is disabled.</para>
<xi:include href="systemd-resolved.service.xml" xpointer="proxy-stub" />
resolved: add an option to control the DNS stub listener
2016-09-01 06:34:29 +08:00
<para>Note that the DNS stub listener is turned off implicitly when its listening address and port are already
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
2023-08-23 00:52:36 +08:00
in use.</para>
<xi:include href="version-info.xml" xpointer="v232"/></listitem>
resolved: add an option to control the DNS stub listener
2016-09-01 06:34:29 +08:00
</varlistentry>
resolve: allow configurable bind address
2020-08-29 15:12:10 +08:00
<varlistentry>
<term><varname>DNSStubListenerExtra=</varname></term>
man: update DNSStubListenerExtra=
2020-09-04 11:58:32 +08:00
<listitem><para>Takes an IPv4 or IPv6 address to listen on. The address may be optionally
prefixed with a protocol name (<literal>udp</literal> or <literal>tcp</literal>) separated with
<literal>:</literal>. If the protocol is not specified, the service will listen on both UDP and
TCP. It may be also optionally suffixed by a numeric port number with separator
<literal>:</literal>. When an IPv6 address is specified with a port number, then the address
must be in the square brackets. If the port is not specified, then the service uses port 53.
Note that this is independent of the primary DNS stub configured with
<varname>DNSStubListener=</varname>, and only configures <emphasis>additional</emphasis>
sockets to listen on. This option can be specified multiple times. If an empty string is
assigned, then the all previous assignments are cleared. Defaults to unset.</para>
<para>Examples:
<programlisting>DNSStubListenerExtra=192.168.10.10
DNSStubListenerExtra=2001:db8:0:f102::10
DNSStubListenerExtra=192.168.10.11:9953
DNSStubListenerExtra=[2001:db8:0:f102::11]:9953
DNSStubListenerExtra=tcp:192.168.10.12
DNSStubListenerExtra=udp:2001:db8:0:f102::12
DNSStubListenerExtra=tcp:192.168.10.13:9953
DNSStubListenerExtra=udp:[2001:db8:0:f102::13]:9953</programlisting>
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
2023-08-23 00:52:36 +08:00
</para>
<xi:include href="version-info.xml" xpointer="v247"/></listitem>
resolve: allow configurable bind address
2020-08-29 15:12:10 +08:00
</varlistentry>
resolve: add option to toggle reading /etc/hosts Workaround for #9718.
2018-07-28 20:46:00 +08:00
<varlistentry>
<term><varname>ReadEtcHosts=</varname></term>
man: document the new option Also correct "stub resolver" → "systemd-resolved" in one other option.
2020-06-03 23:01:34 +08:00
<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.
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
2023-08-23 00:52:36 +08:00
</para>
<xi:include href="version-info.xml" xpointer="v240"/></listitem>
resolve: add option to toggle reading /etc/hosts Workaround for #9718.
2018-07-28 20:46:00 +08:00
</varlistentry>
man: document the new option Also correct "stub resolver" → "systemd-resolved" in one other option.
2020-06-03 23:01:34 +08:00
<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
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
2023-08-23 00:52:36 +08:00
Statement</ulink>, and may create a privacy and security risk.</para>
<xi:include href="version-info.xml" xpointer="v246"/></listitem>
man: document the new option Also correct "stub resolver" → "systemd-resolved" in one other option.
2020-06-03 23:01:34 +08:00
</varlistentry>
resolved: added serve stale feature implementation of RFC 8767 serve stale feature to keep the DNS resource records beyond TTL to return them as stale records in case of upstream server is not reachable or returns negative response. SD_RESOLVED_NO_STALE flag has been added to disable serving stale records via dbus. added serve stale test cases to TEST-75-RESOLVED Fixes: #21815
2023-06-08 21:12:11 +08:00
<varlistentry>
<term>StaleRetentionSec=<replaceable>SECONDS</replaceable></term>
man: more hyperlinks and other fixes Closes https://github.com/systemd/systemd/issues/29814.
2023-11-06 21:59:00 +08:00
<listitem><para>Takes a duration value, which determines the length of time DNS resource records can
be retained in the cache beyond their Time To Live (TTL). This allows these records to be returned as
stale records. By default, this value is set to zero, meaning that DNS resource records are not
stored in the cache after their TTL expires.</para>
<para>This is useful when a DNS server failure occurs or becomes unreachable. In such cases,
<citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry>
continues to use the stale records to answer DNS queries, particularly when no valid response can be
obtained from the upstream DNS servers. However, this doesn't apply to NXDOMAIN responses, as those
are still perfectly valid responses. This feature enhances resilience against DNS infrastructure
failures and outages.</para>
<para><command>systemd-resolved</command> always attempts to reach the upstream DNS servers first,
before providing the client application with any stale data. If this feature is enabled, cache will
not be flushed when changing servers.</para>
man: add version info This tries to add information about when each option was added. It goes back to version 183. The version info is included from a separate file to allow generating it, which would allow more control on the formatting of the final output.
2023-08-23 00:52:36 +08:00
<xi:include href="version-info.xml" xpointer="v254"/>
resolved: added serve stale feature implementation of RFC 8767 serve stale feature to keep the DNS resource records beyond TTL to return them as stale records in case of upstream server is not reachable or returns negative response. SD_RESOLVED_NO_STALE flag has been added to disable serving stale records via dbus. added serve stale test cases to TEST-75-RESOLVED Fixes: #21815
2023-06-08 21:12:11 +08:00
</listitem>
</varlistentry>
Reindent man pages to 2ch
2015-02-04 10:14:13 +08:00
</variablelist>
</refsect1>
<refsect1>
<title>See Also</title>
man: use <simplelist> for 'See also' sections This is just a slight markup improvement; there should be no difference in rendering.
2023-12-23 02:09:32 +08:00
<para><simplelist type="inline">
<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>dnssec-trust-anchors.d</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
<member><citerefentry project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
</simplelist></para>
Reindent man pages to 2ch
2015-02-04 10:14:13 +08:00
</refsect1>
resolved: add daemon to manage resolv.conf Also remove the equivalent functionality from networkd.
2014-05-19 04:10:48 +08:00
</refentry>
Reference in New Issue Copy Permalink