2 <!DOCTYPE refentry PUBLIC
"-//OASIS//DTD DocBook XML V4.2//EN"
3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
6 This file is part of systemd.
8 Copyright 2016 Lennart Poettering
10 systemd is free software; you can redistribute it and/or modify it
11 under the terms of the GNU Lesser General Public License as published by
12 the Free Software Foundation; either version 2.1 of the License, or
13 (at your option) any later version.
15 systemd is distributed in the hope that it will be useful, but
16 WITHOUT ANY WARRANTY; without even the implied warranty of
17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18 Lesser General Public License for more details.
20 You should have received a copy of the GNU Lesser General Public License
21 along with systemd; If not, see <http://www.gnu.org/licenses/>.
24 <refentry id=
"systemd-resolve" conditional='ENABLE_RESOLVE'
25 xmlns:
xi=
"http://www.w3.org/2001/XInclude">
28 <title>systemd-resolve
</title>
29 <productname>systemd
</productname>
33 <contrib>Developer
</contrib>
34 <firstname>Lennart
</firstname>
35 <surname>Poettering
</surname>
36 <email>lennart@poettering.net
</email>
42 <refentrytitle>systemd-resolve
</refentrytitle>
43 <manvolnum>1</manvolnum>
47 <refname>systemd-resolve
</refname>
48 <refpurpose>Resolve domain names, IPV4 and IPv6 addresses, DNS resource records, and services
</refpurpose>
53 <command>systemd-resolve
</command>
54 <arg choice=
"opt" rep=
"repeat">OPTIONS
</arg>
55 <arg choice=
"plain" rep=
"repeat"><replaceable>HOSTNAME
</replaceable></arg>
59 <command>systemd-resolve
</command>
60 <arg choice=
"opt" rep=
"repeat">OPTIONS
</arg>
61 <arg choice=
"plain" rep=
"repeat"><replaceable>ADDRESS
</replaceable></arg>
65 <command>systemd-resolve
</command>
66 <arg choice=
"opt" rep=
"repeat">OPTIONS
</arg>
67 <command> --type=
<replaceable>TYPE
</replaceable></command>
68 <arg choice=
"plain" rep=
"repeat"><replaceable>DOMAIN
</replaceable></arg>
72 <command>systemd-resolve
</command>
73 <arg choice=
"opt" rep=
"repeat">OPTIONS
</arg>
74 <command> --service
</command>
75 <arg choice=
"plain"><arg choice=
"opt"><arg choice=
"opt"><replaceable>NAME
</replaceable></arg>
76 <replaceable>TYPE
</replaceable></arg> <replaceable>DOMAIN
</replaceable></arg>
80 <command>systemd-resolve
</command>
81 <arg choice=
"opt" rep=
"repeat">OPTIONS
</arg>
82 <command> --openpgp
</command>
83 <arg choice=
"plain"><replaceable>USER@DOMAIN
</replaceable></arg>
87 <command>systemd-resolve
</command>
88 <arg choice=
"opt" rep=
"repeat">OPTIONS
</arg>
89 <command> --tlsa
</command>
90 <arg choice=
"plain"><replaceable>DOMAIN
<optional>:PORT
</optional></replaceable></arg>
94 <command>systemd-resolve
</command>
95 <arg choice=
"opt" rep=
"repeat">OPTIONS
</arg>
96 <command> --statistics
</command>
100 <command>systemd-resolve
</command>
101 <arg choice=
"opt" rep=
"repeat">OPTIONS
</arg>
102 <command> --reset-statistics
</command>
108 <title>Description
</title>
110 <para><command>systemd-resolve
</command> may be used to resolve domain names, IPv4 and IPv6 addresses, DNS resource
111 records and services with the
112 <citerefentry><refentrytitle>systemd-resolved.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry>
113 resolver service. By default, the specified list of parameters will be resolved as hostnames, retrieving their IPv4
114 and IPv6 addresses. If the parameters specified are formatted as IPv4 or IPv6 operation the reverse operation is
115 done, and a hostname is retrieved for the specified addresses.
</para>
117 <para>The program's output contains information about the protocol used for the look-up and on which network
118 interface the data was discovered. It also contains information on whether the information could be
119 authenticated. All data for which local DNSSEC validation succeeds is considered authenticated. Moreover all data
120 originating from local, trusted sources is also reported authenticated, including resolution of the local host
121 name, the
<literal>localhost
</literal> host name or all data from
<filename>/etc/hosts
</filename>.
</para>
123 <para>The
<option>--type=
</option> switch may be used to specify a DNS resource record type (A, AAAA, SOA, MX, …) in
124 order to request a specific DNS resource record, instead of the address or reverse address lookups.
125 The special value
<literal>help
</literal> may be used to list known values.
</para>
127 <para>The
<option>--service
</option> switch may be used to resolve
<ulink
128 url=
"https://tools.ietf.org/html/rfc2782">SRV
</ulink> and
<ulink
129 url=
"https://tools.ietf.org/html/rfc6763">DNS-SD
</ulink> services (see below). In this mode, between one and three
130 arguments are required. If three parameters are passed the first is assumed to be the DNS-SD service name, the
131 second the SRV service type, and the third the domain to search in. In this case a full DNS-SD style SRV and TXT
132 lookup is executed. If only two parameters are specified, the first is assumed to be the SRV service type, and the
133 second the domain to look in. In this case no TXT RR is requested. Finally, if only one parameter is specified, it
134 is assumed to be a domain name, that is already prefixed with an SRV type, and an SRV lookup is done (no
137 <para>The
<option>--openpgp
</option> switch may be used to query PGP keys stored as
138 <ulink url=
"https://tools.ietf.org/html/rfc7929">OPENPGPKEY
</ulink> resource records.
139 When this option is specified one or more e-mail address must be specified.
</para>
141 <para>The
<option>--tlsa
</option> switch maybe be used to query TLS public
143 <ulink url=
"https://tools.ietf.org/html/rfc6698">TLSA
</ulink> resource records.
144 When this option is specified one or more domain names must be specified.
</para>
146 <para>The
<option>--statistics
</option> switch may be used to show resolver statistics, including information about
147 the number of successful and failed DNSSEC validations.
</para>
149 <para>The
<option>--reset-statistics
</option> may be used to reset various statistics counters maintained the
150 resolver, including those shown in the
<option>--statistics
</option> output. This operation requires root
155 <title>Options
</title>
158 <term><option>-
4</option></term>
159 <term><option>-
6</option></term>
161 <listitem><para>By default, when resolving a hostname, both IPv4 and IPv6
162 addresses are acquired. By specifying
<option>-
4</option> only IPv4 addresses are requested, by specifying
163 <option>-
6</option> only IPv6 addresses are requested.
</para>
168 <term><option>-i
</option> <replaceable>INTERFACE
</replaceable></term>
169 <term><option>--interface=
</option><replaceable>INTERFACE
</replaceable></term>
171 <listitem><para>Specifies the network interface to execute the query on. This may either be specified as numeric
172 interface index or as network interface string (e.g.
<literal>en0
</literal>). Note that this option has no
173 effect if system-wide DNS configuration (as configured in
<filename>/etc/resolv.conf
</filename> or
174 <filename>/etc/systemd/resolve.conf
</filename>) in place of per-link configuration is used.
</para></listitem>
178 <term><option>-p
</option> <replaceable>PROTOCOL
</replaceable></term>
179 <term><option>--protocol=
</option><replaceable>PROTOCOL
</replaceable></term>
181 <listitem><para>Specifies the network protocol for the query. May be one of
<literal>dns
</literal>
182 (i.e. classic unicast DNS),
<literal>llmnr
</literal> (
<ulink
183 url=
"https://tools.ietf.org/html/rfc4795">Link-Local Multicast Name Resolution
</ulink>),
184 <literal>llmnr-ipv4
</literal>,
<literal>llmnr-ipv6
</literal> (LLMNR via the indicated underlying IP
185 protocols),
<literal>mdns
</literal> (
<ulink url=
"https://www.ietf.org/rfc/rfc6762.txt">Multicast DNS
</ulink>),
186 <literal>mdns-ipv4
</literal>,
<literal>mdns-ipv6
</literal> (MDNS via the indicated underlying IP protocols).
187 By default the lookup is done via all protocols suitable for the lookup. If used, limits the set of
188 protocols that may be used. Use this option multiple times to enable resolving via multiple protocols at the
189 same time. The setting
<literal>llmnr
</literal> is identical to specifying this switch once with
190 <literal>llmnr-ipv4
</literal> and once via
<literal>llmnr-ipv6
</literal>. Note that this option does not force
191 the service to resolve the operation with the specified protocol, as that might require a suitable network
192 interface and configuration.
193 The special value
<literal>help
</literal> may be used to list known values.
198 <term><option>-t
</option> <replaceable>TYPE
</replaceable></term>
199 <term><option>--type=
</option><replaceable>TYPE
</replaceable></term>
200 <term><option>-c
</option> <replaceable>CLASS
</replaceable></term>
201 <term><option>--class=
</option><replaceable>CLASS
</replaceable></term>
203 <listitem><para>Specifies the DNS resource record type (e.g. A, AAAA, MX, …) and class (e.g. IN, ANY, …) to
204 look up. If these options are used a DNS resource record set matching the specified class and type is
205 requested. The class defaults to IN if only a type is specified.
206 The special value
<literal>help
</literal> may be used to list known values.
211 <term><option>--service
</option></term>
213 <listitem><para>Enables service resolution. This enables DNS-SD and simple SRV service resolution, depending
214 on the specified list of parameters (see above).
</para></listitem>
218 <term><option>--service-address=
</option><replaceable>BOOL
</replaceable></term>
220 <listitem><para>Takes a boolean parameter. If true (the default), when doing a service lookup with
221 <option>--service
</option> the hostnames contained in the SRV resource records are resolved as well.
</para></listitem>
225 <term><option>--service-txt=
</option><replaceable>BOOL
</replaceable></term>
227 <listitem><para>Takes a boolean parameter. If true (the default), when doing a DNS-SD service lookup with
228 <option>--service
</option> the TXT service metadata record is resolved as well.
</para></listitem>
232 <term><option>--openpgp
</option></term>
234 <listitem><para>Enables OPENPGPKEY resource record resolution (see above). Specified e-mail
235 addresses are converted to the corresponding DNS domain name, and any OPENPGPKEY keys are
236 printed.
</para></listitem>
240 <term><option>--tlsa
</option></term>
242 <listitem><para>Enables TLSA resource record resolution (see above).
243 A query will be performed for each of the specified names prefixed with
245 (
<literal>_
<replaceable>port
</replaceable>._
<replaceable>family
</replaceable>.
<replaceable>domain
</replaceable></literal>).
246 The port number may be specified after a colon
247 (
<literal>:
</literal>), otherwise
<constant>443</constant> will be used
248 by default. The family may be specified as an argument after
249 <option>--tlsa
</option>, otherwise
<constant>tcp
</constant> will be
250 used.
</para></listitem>
254 <term><option>--cname=
</option><replaceable>BOOL
</replaceable></term>
256 <listitem><para>Takes a boolean parameter. If true (the default), DNS CNAME or DNAME redirections are
257 followed. Otherwise, if a CNAME or DNAME record is encountered while resolving, an error is
258 returned.
</para></listitem>
262 <term><option>--search=
</option><replaceable>BOOL
</replaceable></term>
264 <listitem><para>Takes a boolean parameter. If true (the default), any specified single-label hostnames will be
265 searched in the domains configured in the search domain list, if it is non-empty. Otherwise, the search domain
266 logic is disabled.
</para></listitem>
270 <term><option>--raw
</option><optional>=payload|packet
</optional></term>
272 <listitem><para>Dump the answer as binary data. If there is no argument or if the argument is
273 <literal>payload
</literal>, the payload of the packet is exported. If the argument is
274 <literal>packet
</literal>, the whole packet is dumped in wire format, prefixed by
275 length specified as a little-endian
64-bit number. This format allows multiple packets
276 to be dumped and unambiguously parsed.
</para></listitem>
280 <term><option>--legend=
</option><replaceable>BOOL
</replaceable></term>
282 <listitem><para>Takes a boolean parameter. If true (the default), column headers and meta information about the
283 query response are shown. Otherwise, this output is suppressed.
</para></listitem>
287 <term><option>--statistics
</option></term>
289 <listitem><para>If specified general resolver statistics are shown, including information whether DNSSEC is
290 enabled and available, as well as resolution and validation statistics.
</para></listitem>
294 <term><option>--reset-statistics
</option></term>
296 <listitem><para>Resets the statistics counters shown in
<option>--statistics
</option> to zero.
</para></listitem>
300 <term><option>--flush-caches
</option></term>
302 <listitem><para>Flushes all DNS resource record caches the service maintains locally. This is mostly equivalent
303 to sending the
<constant>SIGUSR2
</constant> to the
<command>systemd-resolved
</command>
304 service.
</para></listitem>
308 <term><option>--reset-server-features
</option></term>
310 <listitem><para>Flushes all feature level information the resolver learnt about specific servers, and ensures
311 that the server feature probing logic is started from the beginning with the next look-up request. This is
312 mostly equivalent to sending the
<constant>SIGRTMIN+
1</constant> to the
<command>systemd-resolved
</command>
313 service.
</para></listitem>
317 <term><option>--status
</option></term>
319 <listitem><para>Shows the global and per-link DNS settings in currently in effect.
</para></listitem>
322 <xi:include href=
"standard-options.xml" xpointer=
"help" />
323 <xi:include href=
"standard-options.xml" xpointer=
"version" />
324 <xi:include href=
"standard-options.xml" xpointer=
"no-pager" />
329 <title>Examples
</title>
332 <title>Retrieve the addresses of the
<literal>www
.0pointer.net
</literal> domain
</title>
334 <programlisting>$ systemd-resolve www
.0pointer.net
335 www
.0pointer.net:
2a01:
238:
43ed:c300:
10c3:bcf3:
3266:da74
338 -- Information acquired via protocol DNS in
611.6ms.
339 -- Data is authenticated: no
344 <title>Retrieve the domain of the
<literal>85.214.157.71</literal> IP address
</title>
346 <programlisting>$ systemd-resolve
85.214.157.71
347 85.214.157.71: gardel
.0pointer.net
349 -- Information acquired via protocol DNS in
1.2997s.
350 -- Data is authenticated: no
355 <title>Retrieve the MX record of the
<literal>yahoo.com
</literal> domain
</title>
357 <programlisting>$ systemd-resolve -t MX yahoo.com --legend=no
358 yahoo.com. IN MX
1 mta7.am0.yahoodns.net
359 yahoo.com. IN MX
1 mta6.am0.yahoodns.net
360 yahoo.com. IN MX
1 mta5.am0.yahoodns.net
365 <title>Resolve an SRV service
</title>
367 <programlisting>$ systemd-resolve --service _xmpp-server._tcp gmail.com
368 _xmpp-server._tcp/gmail.com: alt1.xmpp-server.l.google.com:
5269 [priority=
20, weight=
0]
370 alt4.xmpp-server.l.google.com:
5269 [priority=
20, weight=
0]
377 <title>Retrieve a PGP key
</title>
379 <programlisting>$ systemd-resolve --openpgp zbyszek@fedoraproject.org
380 d08ee310438ca124a6149ea5cc21b6313b390dce485576eff96f8722._openpgpkey.fedoraproject.org. IN OPENPGPKEY
381 mQINBFBHPMsBEACeInGYJCb+
7TurKfb6wGyTottCDtiSJB310i37/
6ZYoeIay/
5soJjlMyf
382 MFQ9T2XNT/
0LM
6gTa
0MpC
1st
9LnzYTMsT
6tzRly
1D
1UbVI
6xw
0g
0vE
5y
2Cjk
3xUwAynCsSs
388 <title>Retrieve a TLS key (
<literal>=tcp
</literal> and
389 <literal>:
443</literal> could be skipped)
</title>
391 <programlisting>$ systemd-resolve --tlsa=tcp fedoraproject.org:
443
392 _443._tcp.fedoraproject.org IN TLSA
0 0 1 19400be5b7a31fb733917700789d2f0a2471c0c9d506c0e504c06c16d7cb17c0
393 -- Cert. usage: CA constraint
394 -- Selector: Full Certificate
395 -- Matching type: SHA-
256
401 <title>See Also
</title>
403 <citerefentry><refentrytitle>systemd
</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
404 <citerefentry><refentrytitle>systemd-resolved.service
</refentrytitle><manvolnum>8</manvolnum></citerefentry>