man/systemd-resolve.xml

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   8   Copyright 2016 Lennart Poettering
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  23
  24 <refentry id="systemd-resolve" conditional='ENABLE_RESOLVE'
  25           xmlns:xi="http://www.w3.org/2001/XInclude">
  26
  27   <refentryinfo>
  28     <title>systemd-resolve</title>
  29     <productname>systemd</productname>
  30
  31     <authorgroup>
  32       <author>
  33         <contrib>Developer</contrib>
  34         <firstname>Lennart</firstname>
  35         <surname>Poettering</surname>
  36         <email>lennart@poettering.net</email>
  37       </author>
  38     </authorgroup>
  39   </refentryinfo>
  40
  41   <refmeta>
  42     <refentrytitle>systemd-resolve</refentrytitle>
  43     <manvolnum>1</manvolnum>
  44   </refmeta>
  45
  46   <refnamediv>
  47     <refname>systemd-resolve</refname>
  48     <refpurpose>Resolve domain names, IPV4 and IPv6 addresses, DNS resource records, and services</refpurpose>
  49   </refnamediv>
  50
  51   <refsynopsisdiv>
  52     <cmdsynopsis>
  53       <command>systemd-resolve</command>
  54       <arg choice="opt" rep="repeat">OPTIONS</arg>
  55       <arg choice="plain" rep="repeat"><replaceable>HOSTNAME</replaceable></arg>
  56     </cmdsynopsis>
  57
  58     <cmdsynopsis>
  59       <command>systemd-resolve</command>
  60       <arg choice="opt" rep="repeat">OPTIONS</arg>
  61       <arg choice="plain" rep="repeat"><replaceable>ADDRESS</replaceable></arg>
  62     </cmdsynopsis>
  63
  64     <cmdsynopsis>
  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>
  69     </cmdsynopsis>
  70
  71     <cmdsynopsis>
  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>
  77     </cmdsynopsis>
  78
  79     <cmdsynopsis>
  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>
  84     </cmdsynopsis>
  85
  86     <cmdsynopsis>
  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>
  91     </cmdsynopsis>
  92
  93     <cmdsynopsis>
  94       <command>systemd-resolve</command>
  95       <arg choice="opt" rep="repeat">OPTIONS</arg>
  96       <command> --statistics</command>
  97     </cmdsynopsis>
  98
  99     <cmdsynopsis>
 100       <command>systemd-resolve</command>
 101       <arg choice="opt" rep="repeat">OPTIONS</arg>
 102       <command> --reset-statistics</command>
 103     </cmdsynopsis>
 104
 105   </refsynopsisdiv>
 106
 107   <refsect1>
 108     <title>Description</title>
 109
 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>
 116
 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>
 122
 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>
 126
 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
 135     TXT).</para>
 136
 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>
 140
 141     <para>The <option>--tlsa</option> switch maybe be used to query TLS public
 142     keys stored as
 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>
 145
 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>
 148
 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
 151     privileges.</para>
 152   </refsect1>
 153
 154   <refsect1>
 155     <title>Options</title>
 156     <variablelist>
 157       <varlistentry>
 158         <term><option>-4</option></term>
 159         <term><option>-6</option></term>
 160
 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>
 164         </listitem>
 165       </varlistentry>
 166
 167       <varlistentry>
 168         <term><option>-i</option> <replaceable>INTERFACE</replaceable></term>
 169         <term><option>--interface=</option><replaceable>INTERFACE</replaceable></term>
 170
 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>
 175       </varlistentry>
 176
 177       <varlistentry>
 178         <term><option>-p</option> <replaceable>PROTOCOL</replaceable></term>
 179         <term><option>--protocol=</option><replaceable>PROTOCOL</replaceable></term>
 180
 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.
 194         </para></listitem>
 195       </varlistentry>
 196
 197       <varlistentry>
 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>
 202
 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.
 207         </para></listitem>
 208       </varlistentry>
 209
 210       <varlistentry>
 211         <term><option>--service</option></term>
 212
 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>
 215       </varlistentry>
 216
 217       <varlistentry>
 218         <term><option>--service-address=</option><replaceable>BOOL</replaceable></term>
 219
 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>
 222       </varlistentry>
 223
 224       <varlistentry>
 225         <term><option>--service-txt=</option><replaceable>BOOL</replaceable></term>
 226
 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>
 229       </varlistentry>
 230
 231       <varlistentry>
 232         <term><option>--openpgp</option></term>
 233
 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>
 237       </varlistentry>
 238
 239       <varlistentry>
 240         <term><option>--tlsa</option></term>
 241
 242         <listitem><para>Enables TLSA resource record resolution (see above).
 243         A query will be performed for each of the specified names prefixed with
 244         the port and family
 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>
 251       </varlistentry>
 252
 253       <varlistentry>
 254         <term><option>--cname=</option><replaceable>BOOL</replaceable></term>
 255
 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>
 259       </varlistentry>
 260
 261       <varlistentry>
 262         <term><option>--search=</option><replaceable>BOOL</replaceable></term>
 263
 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>
 267       </varlistentry>
 268
 269       <varlistentry>
 270         <term><option>--raw</option><optional>=payload|packet</optional></term>
 271
 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>
 277       </varlistentry>
 278
 279       <varlistentry>
 280         <term><option>--legend=</option><replaceable>BOOL</replaceable></term>
 281
 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>
 284       </varlistentry>
 285
 286       <varlistentry>
 287         <term><option>--statistics</option></term>
 288
 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>
 291       </varlistentry>
 292
 293       <varlistentry>
 294         <term><option>--reset-statistics</option></term>
 295
 296         <listitem><para>Resets the statistics counters shown in <option>--statistics</option> to zero.</para></listitem>
 297       </varlistentry>
 298
 299       <varlistentry>
 300         <term><option>--flush-caches</option></term>
 301
 302         <listitem><para>Flushes all DNS resource record caches the service maintains locally.</para></listitem>
 303       </varlistentry>
 304
 305       <varlistentry>
 306         <term><option>--status</option></term>
 307
 308         <listitem><para>Shows the global and per-link DNS settings in currently in effect.</para></listitem>
 309       </varlistentry>
 310
 311       <xi:include href="standard-options.xml" xpointer="help" />
 312       <xi:include href="standard-options.xml" xpointer="version" />
 313       <xi:include href="standard-options.xml" xpointer="no-pager" />
 314     </variablelist>
 315   </refsect1>
 316
 317   <refsect1>
 318     <title>Examples</title>
 319
 320     <example>
 321       <title>Retrieve the addresses of the <literal>www.0pointer.net</literal> domain</title>
 322
 323       <programlisting>$ systemd-resolve www.0pointer.net
 324 www.0pointer.net: 2a01:238:43ed:c300:10c3:bcf3:3266:da74
 325                   85.214.157.71
 326
 327 -- Information acquired via protocol DNS in 611.6ms.
 328 -- Data is authenticated: no
 329 </programlisting>
 330     </example>
 331
 332     <example>
 333       <title>Retrieve the domain of the <literal>85.214.157.71</literal> IP address</title>
 334
 335       <programlisting>$ systemd-resolve 85.214.157.71
 336 85.214.157.71: gardel.0pointer.net
 337
 338 -- Information acquired via protocol DNS in 1.2997s.
 339 -- Data is authenticated: no
 340 </programlisting>
 341     </example>
 342
 343     <example>
 344       <title>Retrieve the MX record of the <literal>yahoo.com</literal> domain</title>
 345
 346       <programlisting>$ systemd-resolve -t MX yahoo.com --legend=no
 347 yahoo.com. IN MX    1 mta7.am0.yahoodns.net
 348 yahoo.com. IN MX    1 mta6.am0.yahoodns.net
 349 yahoo.com. IN MX    1 mta5.am0.yahoodns.net
 350 </programlisting>
 351     </example>
 352
 353     <example>
 354       <title>Resolve an SRV service</title>
 355
 356       <programlisting>$ systemd-resolve --service _xmpp-server._tcp gmail.com
 357 _xmpp-server._tcp/gmail.com: alt1.xmpp-server.l.google.com:5269 [priority=20, weight=0]
 358                              173.194.210.125
 359                              alt4.xmpp-server.l.google.com:5269 [priority=20, weight=0]
 360                              173.194.65.125
 361                              …
 362 </programlisting>
 363     </example>
 364
 365     <example>
 366       <title>Retrieve a PGP key</title>
 367
 368       <programlisting>$ systemd-resolve --openpgp zbyszek@fedoraproject.org
 369 d08ee310438ca124a6149ea5cc21b6313b390dce485576eff96f8722._openpgpkey.fedoraproject.org. IN OPENPGPKEY
 370         mQINBFBHPMsBEACeInGYJCb+7TurKfb6wGyTottCDtiSJB310i37/6ZYoeIay/5soJjlMyf
 371         MFQ9T2XNT/0LM6gTa0MpC1st9LnzYTMsT6tzRly1D1UbVI6xw0g0vE5y2Cjk3xUwAynCsSs
 372         …
 373 </programlisting>
 374     </example>
 375
 376     <example>
 377       <title>Retrieve a TLS key (<literal>=tcp</literal> and
 378       <literal>:443</literal> could be skipped)</title>
 379
 380       <programlisting>$ systemd-resolve --tlsa=tcp fedoraproject.org:443
 381 _443._tcp.fedoraproject.org IN TLSA 0 0 1 19400be5b7a31fb733917700789d2f0a2471c0c9d506c0e504c06c16d7cb17c0
 382         -- Cert. usage: CA constraint
 383         -- Selector: Full Certificate
 384         -- Matching type: SHA-256
 385 </programlisting>
 386     </example>
 387   </refsect1>
 388
 389   <refsect1>
 390     <title>See Also</title>
 391     <para>
 392       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 393       <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 394     </para>
 395   </refsect1>
 396 </refentry>