man/systemd-resolve.xml

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  10   Copyright 2016 Lennart Poettering
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  25
  26 <refentry id="systemd-resolve" conditional='ENABLE_RESOLVE'
  27           xmlns:xi="http://www.w3.org/2001/XInclude">
  28
  29   <refentryinfo>
  30     <title>systemd-resolve</title>
  31     <productname>systemd</productname>
  32
  33     <authorgroup>
  34       <author>
  35         <contrib>Developer</contrib>
  36         <firstname>Lennart</firstname>
  37         <surname>Poettering</surname>
  38         <email>lennart@poettering.net</email>
  39       </author>
  40     </authorgroup>
  41   </refentryinfo>
  42
  43   <refmeta>
  44     <refentrytitle>systemd-resolve</refentrytitle>
  45     <manvolnum>1</manvolnum>
  46   </refmeta>
  47
  48   <refnamediv>
  49     <refname>systemd-resolve</refname>
  50     <refpurpose>Resolve domain names, IPV4 and IPv6 addresses, DNS resource records, and services</refpurpose>
  51   </refnamediv>
  52
  53   <refsynopsisdiv>
  54     <cmdsynopsis>
  55       <command>systemd-resolve</command>
  56       <arg choice="opt" rep="repeat">OPTIONS</arg>
  57       <arg choice="plain" rep="repeat"><replaceable>HOSTNAME</replaceable></arg>
  58     </cmdsynopsis>
  59
  60     <cmdsynopsis>
  61       <command>systemd-resolve</command>
  62       <arg choice="opt" rep="repeat">OPTIONS</arg>
  63       <arg choice="plain" rep="repeat"><replaceable>ADDRESS</replaceable></arg>
  64     </cmdsynopsis>
  65
  66     <cmdsynopsis>
  67       <command>systemd-resolve</command>
  68       <arg choice="opt" rep="repeat">OPTIONS</arg>
  69       <command> --type=<replaceable>TYPE</replaceable></command>
  70       <arg choice="plain" rep="repeat"><replaceable>DOMAIN</replaceable></arg>
  71     </cmdsynopsis>
  72
  73     <cmdsynopsis>
  74       <command>systemd-resolve</command>
  75       <arg choice="opt" rep="repeat">OPTIONS</arg>
  76       <command> --service</command>
  77       <arg choice="plain"><arg choice="opt"><arg choice="opt"><replaceable>NAME</replaceable></arg>
  78       <replaceable>TYPE</replaceable></arg> <replaceable>DOMAIN</replaceable></arg>
  79     </cmdsynopsis>
  80
  81     <cmdsynopsis>
  82       <command>systemd-resolve</command>
  83       <arg choice="opt" rep="repeat">OPTIONS</arg>
  84       <command> --openpgp</command>
  85       <arg choice="plain"><replaceable>USER@DOMAIN</replaceable></arg>
  86     </cmdsynopsis>
  87
  88     <cmdsynopsis>
  89       <command>systemd-resolve</command>
  90       <arg choice="opt" rep="repeat">OPTIONS</arg>
  91       <command> --tlsa</command>
  92       <arg choice="plain"><replaceable>DOMAIN<optional>:PORT</optional></replaceable></arg>
  93     </cmdsynopsis>
  94
  95     <cmdsynopsis>
  96       <command>systemd-resolve</command>
  97       <arg choice="opt" rep="repeat">OPTIONS</arg>
  98       <command> --statistics</command>
  99     </cmdsynopsis>
 100
 101     <cmdsynopsis>
 102       <command>systemd-resolve</command>
 103       <arg choice="opt" rep="repeat">OPTIONS</arg>
 104       <command> --reset-statistics</command>
 105     </cmdsynopsis>
 106
 107     <cmdsynopsis>
 108       <command>systemd-resolve</command>
 109       <arg choice="opt" rep="repeat">OPTIONS</arg>
 110       <command> --flush-caches</command>
 111     </cmdsynopsis>
 112
 113     <cmdsynopsis>
 114       <command>systemd-resolve</command>
 115       <arg choice="opt" rep="repeat">OPTIONS</arg>
 116       <command> --reset-server-features</command>
 117     </cmdsynopsis>
 118
 119     <cmdsynopsis>
 120       <command>systemd-resolve</command>
 121       <arg choice="opt" rep="repeat">OPTIONS</arg>
 122       <command> --status</command>
 123     </cmdsynopsis>
 124
 125     <cmdsynopsis>
 126       <command>systemd-resolve</command>
 127       <arg choice="opt" rep="repeat">OPTIONS</arg>
 128       <command> --set-dns=<replaceable>SERVER</replaceable></command> <command> --set-domain=<replaceable>DOMAIN</replaceable> --set-llmnr=<replaceable>MODE</replaceable> --set-mdns=<replaceable>MODE</replaceable> --set-dnssec=<replaceable>MODE</replaceable> --set-nta=<replaceable>DOMAIN</replaceable></command>
 129     </cmdsynopsis>
 130
 131     <cmdsynopsis>
 132       <command>systemd-resolve</command>
 133       <arg choice="opt" rep="repeat">OPTIONS</arg>
 134       <command> --revert</command>
 135     </cmdsynopsis>
 136
 137   </refsynopsisdiv>
 138
 139   <refsect1>
 140     <title>Description</title>
 141
 142     <para><command>systemd-resolve</command> may be used to resolve domain names, IPv4 and IPv6 addresses, DNS resource
 143     records and services with the
 144     <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 145     resolver service. By default, the specified list of parameters will be resolved as hostnames, retrieving their IPv4
 146     and IPv6 addresses. If the parameters specified are formatted as IPv4 or IPv6 operation the reverse operation is
 147     done, and a hostname is retrieved for the specified addresses.</para>
 148
 149     <para>The program's output contains information about the protocol used for the look-up and on which network
 150     interface the data was discovered. It also contains information on whether the information could be
 151     authenticated. All data for which local DNSSEC validation succeeds is considered authenticated. Moreover all data
 152     originating from local, trusted sources is also reported authenticated, including resolution of the local host
 153     name, the <literal>localhost</literal> host name or all data from <filename>/etc/hosts</filename>.</para>
 154
 155     <para>The <option>--type=</option> switch may be used to specify a DNS resource record type (A, AAAA, SOA, MX, …) in
 156     order to request a specific DNS resource record, instead of the address or reverse address lookups.
 157     The special value <literal>help</literal> may be used to list known values.</para>
 158
 159     <para>The <option>--service</option> switch may be used to resolve <ulink
 160     url="https://tools.ietf.org/html/rfc2782">SRV</ulink> and <ulink
 161     url="https://tools.ietf.org/html/rfc6763">DNS-SD</ulink> services (see below). In this mode, between one and three
 162     arguments are required. If three parameters are passed the first is assumed to be the DNS-SD service name, the
 163     second the SRV service type, and the third the domain to search in. In this case a full DNS-SD style SRV and TXT
 164     lookup is executed. If only two parameters are specified, the first is assumed to be the SRV service type, and the
 165     second the domain to look in. In this case no TXT RR is requested. Finally, if only one parameter is specified, it
 166     is assumed to be a domain name, that is already prefixed with an SRV type, and an SRV lookup is done (no
 167     TXT).</para>
 168
 169     <para>The <option>--openpgp</option> switch may be used to query PGP keys stored as
 170     <ulink url="https://tools.ietf.org/html/rfc7929">OPENPGPKEY</ulink> resource records.
 171     When this option is specified one or more e-mail address must be specified.</para>
 172
 173     <para>The <option>--tlsa</option> switch maybe be used to query TLS public
 174     keys stored as
 175     <ulink url="https://tools.ietf.org/html/rfc6698">TLSA</ulink> resource records.
 176     When this option is specified one or more domain names must be specified.</para>
 177
 178     <para>The <option>--statistics</option> switch may be used to show resolver statistics, including information about
 179     the number of successful and failed DNSSEC validations.</para>
 180
 181     <para>The <option>--reset-statistics</option> may be used to reset various statistics counters maintained the
 182     resolver, including those shown in the <option>--statistics</option> output. This operation requires root
 183     privileges.</para>
 184   </refsect1>
 185
 186   <refsect1>
 187     <title>Options</title>
 188     <variablelist>
 189       <varlistentry>
 190         <term><option>-4</option></term>
 191         <term><option>-6</option></term>
 192
 193         <listitem><para>By default, when resolving a hostname, both IPv4 and IPv6
 194         addresses are acquired. By specifying <option>-4</option> only IPv4 addresses are requested, by specifying
 195         <option>-6</option> only IPv6 addresses are requested.</para>
 196         </listitem>
 197       </varlistentry>
 198
 199       <varlistentry>
 200         <term><option>-i</option> <replaceable>INTERFACE</replaceable></term>
 201         <term><option>--interface=</option><replaceable>INTERFACE</replaceable></term>
 202
 203         <listitem><para>Specifies the network interface to execute the query on. This may either be specified as numeric
 204         interface index or as network interface string (e.g. <literal>en0</literal>). Note that this option has no
 205         effect if system-wide DNS configuration (as configured in <filename>/etc/resolv.conf</filename> or
 206         <filename>/etc/systemd/resolve.conf</filename>) in place of per-link configuration is used.</para></listitem>
 207       </varlistentry>
 208
 209       <varlistentry>
 210         <term><option>-p</option> <replaceable>PROTOCOL</replaceable></term>
 211         <term><option>--protocol=</option><replaceable>PROTOCOL</replaceable></term>
 212
 213         <listitem><para>Specifies the network protocol for the query. May be one of <literal>dns</literal>
 214         (i.e. classic unicast DNS), <literal>llmnr</literal> (<ulink
 215         url="https://tools.ietf.org/html/rfc4795">Link-Local Multicast Name Resolution</ulink>),
 216         <literal>llmnr-ipv4</literal>, <literal>llmnr-ipv6</literal> (LLMNR via the indicated underlying IP
 217         protocols), <literal>mdns</literal> (<ulink url="https://www.ietf.org/rfc/rfc6762.txt">Multicast DNS</ulink>),
 218         <literal>mdns-ipv4</literal>, <literal>mdns-ipv6</literal> (MDNS via the indicated underlying IP protocols).
 219         By default the lookup is done via all protocols suitable for the lookup. If used, limits the set of
 220         protocols that may be used. Use this option multiple times to enable resolving via multiple protocols at the
 221         same time. The setting <literal>llmnr</literal> is identical to specifying this switch once with
 222         <literal>llmnr-ipv4</literal> and once via <literal>llmnr-ipv6</literal>. Note that this option does not force
 223         the service to resolve the operation with the specified protocol, as that might require a suitable network
 224         interface and configuration.
 225         The special value <literal>help</literal> may be used to list known values.
 226         </para></listitem>
 227       </varlistentry>
 228
 229       <varlistentry>
 230         <term><option>-t</option> <replaceable>TYPE</replaceable></term>
 231         <term><option>--type=</option><replaceable>TYPE</replaceable></term>
 232         <term><option>-c</option> <replaceable>CLASS</replaceable></term>
 233         <term><option>--class=</option><replaceable>CLASS</replaceable></term>
 234
 235         <listitem><para>Specifies the DNS resource record type (e.g. A, AAAA, MX, …) and class (e.g. IN, ANY, …) to
 236         look up. If these options are used a DNS resource record set matching the specified class and type is
 237         requested. The class defaults to IN if only a type is specified.
 238         The special value <literal>help</literal> may be used to list known values.
 239         </para></listitem>
 240       </varlistentry>
 241
 242       <varlistentry>
 243         <term><option>--service</option></term>
 244
 245         <listitem><para>Enables service resolution. This enables DNS-SD and simple SRV service resolution, depending
 246         on the specified list of parameters (see above).</para></listitem>
 247       </varlistentry>
 248
 249       <varlistentry>
 250         <term><option>--service-address=</option><replaceable>BOOL</replaceable></term>
 251
 252         <listitem><para>Takes a boolean parameter. If true (the default), when doing a service lookup with
 253         <option>--service</option> the hostnames contained in the SRV resource records are resolved as well.</para></listitem>
 254       </varlistentry>
 255
 256       <varlistentry>
 257         <term><option>--service-txt=</option><replaceable>BOOL</replaceable></term>
 258
 259         <listitem><para>Takes a boolean parameter. If true (the default), when doing a DNS-SD service lookup with
 260         <option>--service</option> the TXT service metadata record is resolved as well.</para></listitem>
 261       </varlistentry>
 262
 263       <varlistentry>
 264         <term><option>--openpgp</option></term>
 265
 266         <listitem><para>Enables OPENPGPKEY resource record resolution (see above). Specified e-mail
 267         addresses are converted to the corresponding DNS domain name, and any OPENPGPKEY keys are
 268         printed.</para></listitem>
 269       </varlistentry>
 270
 271       <varlistentry>
 272         <term><option>--tlsa</option></term>
 273
 274         <listitem><para>Enables TLSA resource record resolution (see above).
 275         A query will be performed for each of the specified names prefixed with
 276         the port and family
 277         (<literal>_<replaceable>port</replaceable>._<replaceable>family</replaceable>.<replaceable>domain</replaceable></literal>).
 278         The port number may be specified after a colon
 279         (<literal>:</literal>), otherwise <constant>443</constant> will be used
 280         by default. The family may be specified as an argument after
 281         <option>--tlsa</option>, otherwise <constant>tcp</constant> will be
 282         used.</para></listitem>
 283       </varlistentry>
 284
 285       <varlistentry>
 286         <term><option>--cname=</option><replaceable>BOOL</replaceable></term>
 287
 288         <listitem><para>Takes a boolean parameter. If true (the default), DNS CNAME or DNAME redirections are
 289         followed. Otherwise, if a CNAME or DNAME record is encountered while resolving, an error is
 290         returned.</para></listitem>
 291       </varlistentry>
 292
 293       <varlistentry>
 294         <term><option>--search=</option><replaceable>BOOL</replaceable></term>
 295
 296         <listitem><para>Takes a boolean parameter. If true (the default), any specified single-label hostnames will be
 297         searched in the domains configured in the search domain list, if it is non-empty. Otherwise, the search domain
 298         logic is disabled.</para></listitem>
 299       </varlistentry>
 300
 301       <varlistentry>
 302         <term><option>--raw</option><optional>=payload|packet</optional></term>
 303
 304         <listitem><para>Dump the answer as binary data. If there is no argument or if the argument is
 305         <literal>payload</literal>, the payload of the packet is exported. If the argument is
 306         <literal>packet</literal>, the whole packet is dumped in wire format, prefixed by
 307         length specified as a little-endian 64-bit number. This format allows multiple packets
 308         to be dumped and unambiguously parsed.</para></listitem>
 309       </varlistentry>
 310
 311       <varlistentry>
 312         <term><option>--legend=</option><replaceable>BOOL</replaceable></term>
 313
 314         <listitem><para>Takes a boolean parameter. If true (the default), column headers and meta information about the
 315         query response are shown. Otherwise, this output is suppressed.</para></listitem>
 316       </varlistentry>
 317
 318       <varlistentry>
 319         <term><option>--statistics</option></term>
 320
 321         <listitem><para>If specified general resolver statistics are shown, including information whether DNSSEC is
 322         enabled and available, as well as resolution and validation statistics.</para></listitem>
 323       </varlistentry>
 324
 325       <varlistentry>
 326         <term><option>--reset-statistics</option></term>
 327
 328         <listitem><para>Resets the statistics counters shown in <option>--statistics</option> to zero.</para></listitem>
 329       </varlistentry>
 330
 331       <varlistentry>
 332         <term><option>--flush-caches</option></term>
 333
 334         <listitem><para>Flushes all DNS resource record caches the service maintains locally. This is mostly equivalent
 335         to sending the <constant>SIGUSR2</constant> to the <command>systemd-resolved</command>
 336         service.</para></listitem>
 337       </varlistentry>
 338
 339       <varlistentry>
 340         <term><option>--reset-server-features</option></term>
 341
 342         <listitem><para>Flushes all feature level information the resolver learnt about specific servers, and ensures
 343         that the server feature probing logic is started from the beginning with the next look-up request. This is
 344         mostly equivalent to sending the <constant>SIGRTMIN+1</constant> to the <command>systemd-resolved</command>
 345         service.</para></listitem>
 346       </varlistentry>
 347
 348       <varlistentry>
 349         <term><option>--status</option></term>
 350
 351         <listitem><para>Shows the global and per-link DNS settings in currently in effect.</para></listitem>
 352       </varlistentry>
 353
 354       <varlistentry>
 355         <term><option>--set-dns=SERVER</option></term>
 356         <term><option>--set-domain=DOMAIN</option></term>
 357         <term><option>--set-llmnr=MODE</option></term>
 358         <term><option>--set-mdns=MODE</option></term>
 359         <term><option>--set-dnssec=MODE</option></term>
 360         <term><option>--set-nta=DOMAIN</option></term>
 361
 362         <listitem><para>Set per-interface DNS configuration. These switches may be used to configure various DNS
 363         settings for network interfaces that aren't managed by
 364         <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>. (These
 365         commands will fail when used on interfaces that are managed by <command>systemd-networkd</command>, please
 366         configure their DNS settings directly inside the <filename>.network</filename> files instead.) These switches
 367         may be used to inform <command>systemd-resolved</command> about per-interface DNS configuration determined
 368         through external means. Multiple of these switches may be passed on a single invocation of
 369         <command>systemd-resolve</command> in order to set multiple configuration options at once. If any of these
 370         switches is used, it must be combined with <option>--interface=</option> to indicate the network interface the
 371         new DNS configuration belongs to. The <option>--set-dns=</option> option expects an IPv4 or IPv6 address
 372         specification of a DNS server to use, and may be used multiple times to define multiple servers for the same
 373         interface. The <option>--set-domain=</option> option expects a valid DNS domain, possibly prefixed with
 374         <literal>~</literal>, and configures a per-interface search or route-only domain. It may be used multiple times
 375         to configure multiple such domains. The <option>--set-llmnr=</option>, <option>--set-mdns=</option> and
 376         <option>--set-dnssec=</option> options may be used to configure the per-interface LLMNR, MulticastDNS and
 377         DNSSEC settings. Finally, <option>--set-nta=</option> may be used to configure additional per-interface DNSSEC
 378         NTA domains and may also be used multiple times. For details about these settings, their possible values and
 379         their effect, see the corresponding options in
 380         <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 381         </listitem>
 382       </varlistentry>
 383
 384       <varlistentry>
 385         <term><option>--revert</option></term>
 386
 387         <listitem><para>Revert the per-interface DNS configuration. This option must be combined with
 388         <option>--interface=</option> to indicate the network interface the DNS configuration shall be reverted on. If
 389         the DNS configuration is reverted all per-interface DNS setting are reset to their defaults, undoing all
 390         effects of <option>--set-dns=</option>, <option>--set-domain=</option>, <option>--set-llmnr=</option>,
 391         <option>--set-mdns=</option>, <option>--set-dnssec=</option>, <option>--set-nta=</option>. Note that when a
 392         network interface disappears all configuration is lost automatically, an explicit reverting is not necessary in
 393         that case.</para></listitem>
 394       </varlistentry>
 395
 396       <xi:include href="standard-options.xml" xpointer="help" />
 397       <xi:include href="standard-options.xml" xpointer="version" />
 398       <xi:include href="standard-options.xml" xpointer="no-pager" />
 399     </variablelist>
 400   </refsect1>
 401
 402   <refsect1>
 403     <title>Examples</title>
 404
 405     <example>
 406       <title>Retrieve the addresses of the <literal>www.0pointer.net</literal> domain</title>
 407
 408       <programlisting>$ systemd-resolve www.0pointer.net
 409 www.0pointer.net: 2a01:238:43ed:c300:10c3:bcf3:3266:da74
 410                   85.214.157.71
 411
 412 -- Information acquired via protocol DNS in 611.6ms.
 413 -- Data is authenticated: no
 414 </programlisting>
 415     </example>
 416
 417     <example>
 418       <title>Retrieve the domain of the <literal>85.214.157.71</literal> IP address</title>
 419
 420       <programlisting>$ systemd-resolve 85.214.157.71
 421 85.214.157.71: gardel.0pointer.net
 422
 423 -- Information acquired via protocol DNS in 1.2997s.
 424 -- Data is authenticated: no
 425 </programlisting>
 426     </example>
 427
 428     <example>
 429       <title>Retrieve the MX record of the <literal>yahoo.com</literal> domain</title>
 430
 431       <programlisting>$ systemd-resolve -t MX yahoo.com --legend=no
 432 yahoo.com. IN MX    1 mta7.am0.yahoodns.net
 433 yahoo.com. IN MX    1 mta6.am0.yahoodns.net
 434 yahoo.com. IN MX    1 mta5.am0.yahoodns.net
 435 </programlisting>
 436     </example>
 437
 438     <example>
 439       <title>Resolve an SRV service</title>
 440
 441       <programlisting>$ systemd-resolve --service _xmpp-server._tcp gmail.com
 442 _xmpp-server._tcp/gmail.com: alt1.xmpp-server.l.google.com:5269 [priority=20, weight=0]
 443                              173.194.210.125
 444                              alt4.xmpp-server.l.google.com:5269 [priority=20, weight=0]
 445                              173.194.65.125
 446                              …
 447 </programlisting>
 448     </example>
 449
 450     <example>
 451       <title>Retrieve a PGP key</title>
 452
 453       <programlisting>$ systemd-resolve --openpgp zbyszek@fedoraproject.org
 454 d08ee310438ca124a6149ea5cc21b6313b390dce485576eff96f8722._openpgpkey.fedoraproject.org. IN OPENPGPKEY
 455         mQINBFBHPMsBEACeInGYJCb+7TurKfb6wGyTottCDtiSJB310i37/6ZYoeIay/5soJjlMyf
 456         MFQ9T2XNT/0LM6gTa0MpC1st9LnzYTMsT6tzRly1D1UbVI6xw0g0vE5y2Cjk3xUwAynCsSs
 457         …
 458 </programlisting>
 459     </example>
 460
 461     <example>
 462       <title>Retrieve a TLS key (<literal>=tcp</literal> and
 463       <literal>:443</literal> could be skipped)</title>
 464
 465       <programlisting>$ systemd-resolve --tlsa=tcp fedoraproject.org:443
 466 _443._tcp.fedoraproject.org IN TLSA 0 0 1 19400be5b7a31fb733917700789d2f0a2471c0c9d506c0e504c06c16d7cb17c0
 467         -- Cert. usage: CA constraint
 468         -- Selector: Full Certificate
 469         -- Matching type: SHA-256
 470 </programlisting>
 471     </example>
 472   </refsect1>
 473
 474   <refsect1>
 475     <title>See Also</title>
 476     <para>
 477       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 478       <citerefentry><refentrytitle>systemd-resolved.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 479       <citerefentry><refentrytitle>systemd.dnssd</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 480       <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 481     </para>
 482   </refsect1>
 483 </refentry>