man/systemd-resolved.service.xml

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   5
   6 <refentry id="systemd-resolved.service" conditional='ENABLE_RESOLVE'>
   7
   8   <refentryinfo>
   9     <title>systemd-resolved.service</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>systemd-resolved.service</refentrytitle>
  15     <manvolnum>8</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>systemd-resolved.service</refname>
  20     <refname>systemd-resolved</refname>
  21     <refpurpose>Network Name Resolution manager</refpurpose>
  22   </refnamediv>
  23
  24   <refsynopsisdiv>
  25     <para><filename>systemd-resolved.service</filename></para>
  26     <para><filename>/usr/lib/systemd/systemd-resolved</filename></para>
  27   </refsynopsisdiv>
  28
  29   <refsect1>
  30     <title>Description</title>
  31
  32     <para><command>systemd-resolved</command> is a system service that provides network name resolution to
  33     local applications. It implements a caching and validating DNS/DNSSEC stub resolver, as well as an LLMNR
  34     and MulticastDNS resolver and responder. Local applications may submit network name resolution requests
  35     via three interfaces:</para>
  36
  37     <itemizedlist>
  38       <listitem><para>The native, fully-featured API <command>systemd-resolved</command> exposes on the bus,
  39       see
  40       <citerefentry><refentrytitle>org.freedesktop.resolve1</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  41       and
  42       <citerefentry><refentrytitle>org.freedesktop.LogControl1</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  43       for details. Usage of this API is generally recommended to clients as it is asynchronous and fully
  44       featured (for example, properly returns DNSSEC validation status and interface scope for addresses as
  45       necessary for supporting link-local networking).</para></listitem>
  46
  47       <listitem><para>The glibc
  48       <citerefentry project='man-pages'><refentrytitle>getaddrinfo</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  49       API as defined by <ulink url="https://tools.ietf.org/html/rfc3493">RFC3493</ulink> and its related
  50       resolver functions, including
  51       <citerefentry project='man-pages'><refentrytitle>gethostbyname</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
  52       This API is widely supported, including beyond the Linux platform. In its current form it does not
  53       expose DNSSEC validation status information however, and is synchronous only. This API is backed by the
  54       glibc Name Service Switch
  55       (<citerefentry project='man-pages'><refentrytitle>nss</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
  56       Usage of the glibc NSS module
  57       <citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry> is
  58       required in order to allow glibc's NSS resolver functions to resolve hostnames via
  59       <command>systemd-resolved</command>.</para></listitem>
  60
  61       <listitem><para>Additionally, <command>systemd-resolved</command> provides a local DNS stub listener on
  62       IP address 127.0.0.53 on the local loopback interface. Programs issuing DNS requests directly,
  63       bypassing any local API may be directed to this stub, in order to connect them to
  64       <command>systemd-resolved</command>. Note however that it is strongly recommended that local programs
  65       use the glibc NSS or bus APIs instead (as described above), as various network resolution concepts
  66       (such as link-local addressing, or LLMNR Unicode domains) cannot be mapped to the unicast DNS
  67       protocol.</para></listitem>
  68     </itemizedlist>
  69
  70     <para>The DNS servers contacted are determined from the global settings in
  71     <filename>/etc/systemd/resolved.conf</filename>, the per-link static settings in
  72     <filename>/etc/systemd/network/*.network</filename> files (in case
  73     <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  74     is used), the per-link dynamic settings received over DHCP, information provided via
  75     <citerefentry><refentrytitle>resolvectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, and any
  76     DNS server information made available by other system services. See
  77     <citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry> and
  78     <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
  79     details about systemd's own configuration files for DNS servers. To improve compatibility,
  80     <filename>/etc/resolv.conf</filename> is read in order to discover configured system DNS servers, but
  81     only if it is not a symlink to <filename>/run/systemd/resolve/stub-resolv.conf</filename>,
  82     <filename>/usr/lib/systemd/resolv.conf</filename> or
  83     <filename>/run/systemd/resolve/resolv.conf</filename> (see below).</para>
  84
  85   </refsect1>
  86
  87   <refsect1>
  88     <title>Synthetic Records</title>
  89
  90     <para><command>systemd-resolved</command> synthesizes DNS resource records (RRs) for the following
  91     cases:</para>
  92
  93     <itemizedlist>
  94       <listitem><para>The local, configured hostname is resolved to all locally configured IP addresses
  95       ordered by their scope, or — if none are configured — the IPv4 address 127.0.0.2 (which is on the local
  96       loopback interface) and the IPv6 address ::1 (which is the local host).</para></listitem>
  97
  98       <listitem><para>The hostnames <literal>localhost</literal> and <literal>localhost.localdomain</literal>
  99       as well as any hostname ending in <literal>.localhost</literal> or
 100       <literal>.localhost.localdomain</literal> are resolved to the IP addresses 127.0.0.1 and ::1.
 101       </para></listitem>
 102
 103       <listitem><para>The hostname <literal>_gateway</literal> is resolved to all current default routing
 104       gateway addresses, ordered by their metric. This assigns a stable hostname to the current gateway,
 105       useful for referencing it independently of the current network configuration state.</para></listitem>
 106
 107       <listitem><para>The hostname <literal>_outbound</literal> is resolved to the local IPv4 and IPv6
 108       addresses that are most likely used for communication with other hosts. This is determined by
 109       requesting a routing decision to the configured default gateways from the kernel and then using the
 110       local IP addresses selected by this decision. This hostname is only available if there is at least one
 111       local default gateway configured. This assigns a stable hostname to the local outbound IP addresses,
 112       useful for referencing them independently of the current network configuration state.</para></listitem>
 113
 114       <listitem><para>The mappings defined in <filename>/etc/hosts</filename> are resolved to their
 115       configured addresses and back, but they will not affect lookups for non-address types (like MX).
 116       Support for <filename>/etc/hosts</filename> may be disabled with <varname>ReadEtcHosts=no</varname>,
 117       see <citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 118       </para></listitem>
 119     </itemizedlist>
 120   </refsect1>
 121
 122   <refsect1>
 123     <title>Protocols and Routing</title>
 124
 125     <para>The lookup requests that <filename>systemd-resolved.service</filename> receives are routed to the
 126     available DNS servers, LLMNR, and MulticastDNS interfaces according to the following rules:</para>
 127
 128     <itemizedlist>
 129       <listitem><para>Names for which synthetic records are generated (the local hostname,
 130       <literal>localhost</literal> and <literal>localdomain</literal>, local gateway, as listed in the
 131       previous section) and addresses configured in <filename>/etc/hosts</filename> are never routed to the
 132       network and a reply is sent immediately.</para></listitem>
 133
 134       <listitem><para>Single-label names are resolved using LLMNR on all local interfaces where LLMNR is
 135       enabled. Lookups for IPv4 addresses are only sent via LLMNR on IPv4, and lookups for IPv6 addresses are
 136       only sent via LLMNR on IPv6. Note that lookups for single-label synthesized names are not routed to
 137       LLMNR, MulticastDNS or unicast DNS.</para></listitem>
 138
 139       <listitem><para>Queries for the address records (A and AAAA) of single-label non-synthesized names are
 140       resolved via unicast DNS using search domains. For any interface which defines search domains, such
 141       look-ups are routed to the servers defined for that interface, suffixed with each of those search
 142       domains. When global search domains are defined, such look-ups are routed to the global servers. For
 143       each search domain, queries are performed by suffixing the name with each of the search domains in
 144       turn. Additionally, lookup of single-label names via unicast DNS may be enabled with the
 145       <varname>ResolveUnicastSingleLabel=yes</varname> setting. The details of which servers are queried and
 146       how the final reply is chosen are described below. Note that this means that address queries for
 147       single-label names are never sent out to remote DNS servers by default, and resolution is only
 148       possible if search domains are defined.</para></listitem>
 149
 150       <listitem><para>Multi-label names with the domain suffix <literal>.local</literal> are resolved using
 151       MulticastDNS on all local interfaces where MulticastDNS is enabled. As with LLMNR, IPv4 address lookups
 152       are sent via IPv4 and IPv6 address lookups are sent via IPv6.</para></listitem>
 153
 154       <listitem><para>Queries for multi-label names are routed via unicast DNS on local interfaces that have
 155       a DNS server configured, plus the globally configured DNS servers if there are any. Which interfaces
 156       are used is determined by the routing logic based on search and route-only domains, described below.
 157       Note that by default, lookups for domains with the <literal>.local</literal> suffix are not routed to
 158       DNS servers, unless the domain is specified explicitly as routing or search domain for the DNS server
 159       and interface. This means that on networks where the <literal>.local</literal> domain is defined in a
 160       site-specific DNS server, explicit search or routing domains need to be configured to make lookups work
 161       within this DNS domain. Note that these days, it's generally recommended to avoid defining
 162       <literal>.local</literal> in a DNS server, as <ulink
 163       url="https://tools.ietf.org/html/rfc6762">RFC6762</ulink> reserves this domain for exclusive
 164       MulticastDNS use.</para></listitem>
 165
 166       <listitem><para>Address lookups (reverse lookups) are routed similarly to multi-label names, with the
 167       exception that addresses from the link-local address range are never routed to unicast DNS and are only
 168       resolved using LLMNR and MulticastDNS (when enabled).</para></listitem>
 169     </itemizedlist>
 170
 171     <para>If lookups are routed to multiple interfaces, the first successful response is returned (thus
 172     effectively merging the lookup zones on all matching interfaces). If the lookup failed on all interfaces,
 173     the last failing response is returned.</para>
 174
 175     <para>Routing of lookups is determined by the per-interface routing domains (search and route-only) and
 176     global search domains. See
 177     <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry> and
 178     <citerefentry><refentrytitle>resolvectl</refentrytitle><manvolnum>1</manvolnum></citerefentry> for a
 179     description how those settings are set dynamically and the discussion of <varname>Domains=</varname> in
 180     <citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry> for a
 181     description of globally configured DNS settings.</para>
 182
 183     <para>The following query routing logic applies for unicast DNS lookups initiated by
 184     <filename>systemd-resolved.service</filename>:</para>
 185
 186     <itemizedlist>
 187       <listitem><para>If a name to look up matches (that is: is equal to or has as suffix) any of the
 188       configured routing domains (search or route-only) of any link, or the globally configured DNS settings,
 189       "best matching" routing domain is determined: the matching one with the most labels. The query is then
 190       sent to all DNS servers of any links or the globally configured DNS servers associated with this "best
 191       matching" routing domain. (Note that more than one link might have this same "best matching" routing
 192       domain configured, in which case the query is sent to all of them in parallel).</para>
 193
 194       <para>In case of single-label names, when search domains are defined, the same logic applies, except
 195       that the name is first suffixed by each of the search domains in turn. Note that this search logic
 196       doesn't apply to any names with at least one dot. Also see the discussion about compatibility with
 197       the traditional glibc resolver below.</para></listitem>
 198
 199       <listitem><para>If a query does not match any configured routing domain (either per-link or global), it
 200       is sent to all DNS servers that are configured on links with the <varname>DefaultRoute=</varname>
 201       option set, as well as the globally configured DNS server.</para></listitem>
 202
 203       <listitem><para>If there is no link configured as <varname>DefaultRoute=</varname> and no global DNS
 204       server configured, one of the compiled-in fallback DNS servers is used.</para></listitem>
 205
 206       <listitem><para>Otherwise the unicast DNS query fails, as no suitable DNS servers can be determined.
 207       </para></listitem>
 208     </itemizedlist>
 209
 210     <para>The <varname>DefaultRoute=</varname> option is a boolean setting configurable with
 211     <command>resolvectl</command> or in <filename>.network</filename> files. If not set, it is implicitly
 212     determined based on the configured DNS domains for a link: if there's a route-only domain other than
 213     <literal>~.</literal>, it defaults to false, otherwise to true.</para>
 214
 215     <para>Effectively this means: in order to support single-label non-synthesized names, define appropriate
 216     search domains. In order to preferably route all DNS queries not explicitly matched by routing domain
 217     configuration to a specific link, configure a <literal>~.</literal> route-only domain on it. This will
 218     ensure that other links will not be considered for these queries (unless they too carry such a routing
 219     domain). In order to route all such DNS queries to a specific link only if no other link is preferred,
 220     set the <varname>DefaultRoute=</varname> option for the link to true and do not configure a
 221     <literal>~.</literal> route-only domain on it. Finally, in order to ensure that a specific link never
 222     receives any DNS traffic not matching any of its configured routing domains, set the
 223     <varname>DefaultRoute=</varname> option for it to false.</para>
 224
 225     <para>See
 226     <citerefentry><refentrytitle>org.freedesktop.resolve1</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 227     for information about the D-Bus APIs <filename>systemd-resolved</filename> provides.</para>
 228   </refsect1>
 229
 230   <refsect1>
 231     <title>Compatibility with the traditional glibc stub resolver</title>
 232
 233     <para>This section provides a short summary of differences in the stub resolver implemented by
 234     <citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry> together
 235     with <command>systemd-resolved</command> and the traditional stub resolver implemented in
 236     <filename>nss-dns</filename>.</para>
 237
 238     <itemizedlist>
 239       <listitem><para>Some names are always resolved internally (see Synthetic Records above). Traditionally
 240       they would be resolved by <filename>nss-files</filename> if provided in
 241       <filename>/etc/hosts</filename>. But note that the details of how a query is constructed are under the
 242       control of the client library. <filename>nss-dns</filename> will first try to resolve names using
 243       search domains and even if those queries are routed to <filename>systemd-resolved</filename>, it will
 244       send them out over the network using the usual rules for multi-label name routing <footnote><para>For
 245       example, if <filename>/etc/resolv.conf</filename> has <programlisting>nameserver 127.0.0.53
 246 search foobar.com barbar.com
 247       </programlisting>and we look up <literal>localhost</literal>, <filename>nss-dns</filename> will send
 248       the following queries to <filename>systemd-resolved</filename> listening on 127.0.0.53:53: first
 249       <literal>localhost.foobar.com</literal>, then <literal>localhost.barbar.com</literal>, and finally
 250       <literal>localhost</literal>. If (hopefully) the first two queries fail,
 251       <filename>systemd-resolved</filename> will synthesize an answer for the third query.</para>
 252
 253       <para>When using <filename>nss-dns</filename> with any search domains, it is thus crucial to always
 254       configure <filename>nss-files</filename> with higher priority and provide mappings for names that
 255       should not be resolved using search domains.</para></footnote>.</para></listitem>
 256
 257       <listitem><para>Single-label names are not resolved for A and AAAA records using unicast DNS (unless
 258       overridden with <varname>ResolveUnicastSingleLabel=</varname>, see
 259       <citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
 260       This is similar to the <option>no-tld-query</option> option being set in
 261       <citerefentry project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 262       </para></listitem>
 263
 264       <listitem><para>Search domains are not used for <emphasis>suffixing</emphasis> of multi-label names.
 265       (Search domains are nevertheless used for lookup <emphasis>routing</emphasis>, for names that were
 266       originally specified as single-label or multi-label.) Any name with at least one dot is always
 267       interpreted as a FQDN. <filename>nss-dns</filename> would resolve names both as relative (using search
 268       domains) and absolute FQDN names. Some names would be resolved as relative first, and after that query
 269       has failed, as absolute, while other names would be resolved in opposite order. The
 270       <varname>ndots</varname> option in <filename>/etc/resolv.conf</filename> was used to control how many
 271       dots the name needs to have to be resolved as relative first. This stub resolver does not implement
 272       this at all: multi-label names are only resolved as FQDNs.<footnote><para>There are currently more than
 273       1500 top-level domain names defined, and new ones are added regularly, often using "attractive" names
 274       that are also likely to be used locally. Not looking up multi-label names in this fashion avoids
 275       fragility in both directions: a valid global name could be obscured by a local name, and resolution of
 276       a relative local name could suddenly break when a new top-level domain is created, or when a new
 277       subdomain of a top-level domain in registered. Resolving any given name as either relative or absolute
 278       avoids this ambiguity.</para></footnote></para></listitem>
 279
 280       <listitem><para>This resolver has a notion of the special <literal>.local</literal> domain used for
 281       MulticastDNS, and will not route queries with that suffix to unicast DNS servers unless explicitly
 282       configured, see above. Also, reverse lookups for link-local addresses are not sent to unicast DNS
 283       servers.</para></listitem>
 284
 285       <listitem><para>This resolver reads and caches <filename>/etc/hosts</filename> internally. (In other
 286       words, <filename>nss-resolve</filename> replaces <filename>nss-files</filename> in addition to
 287       <filename>nss-dns</filename>). Entries in <filename>/etc/hosts</filename> have highest priority.</para>
 288       </listitem>
 289
 290       <listitem><para>This resolver also implements LLMNR and MulticastDNS in addition to the classic unicast
 291       DNS protocol, and will resolve single-label names using LLMNR (when enabled) and names ending in
 292       <literal>.local</literal> using MulticastDNS (when enabled).</para></listitem>
 293
 294       <listitem><para>Environment variables <varname>$LOCALDOMAIN</varname> and
 295       <varname>$RES_OPTIONS</varname> described in
 296       <citerefentry project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 297       are not supported currently.</para></listitem>
 298     </itemizedlist>
 299   </refsect1>
 300
 301   <refsect1>
 302     <title><filename>/etc/resolv.conf</filename></title>
 303
 304     <para>Four modes of handling <filename>/etc/resolv.conf</filename> (see
 305     <citerefentry project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>) are
 306     supported:</para>
 307
 308     <itemizedlist>
 309       <listitem><para><command>systemd-resolved</command> maintains the
 310       <filename>/run/systemd/resolve/stub-resolv.conf</filename> file for compatibility with traditional
 311       Linux programs. This file may be symlinked from <filename>/etc/resolv.conf</filename>. This file lists
 312       the 127.0.0.53 DNS stub (see above) as the only DNS server. It also contains a list of search domains
 313       that are in use by systemd-resolved. The list of search domains is always kept up-to-date. Note that
 314       <filename>/run/systemd/resolve/stub-resolv.conf</filename> should not be used directly by applications,
 315       but only through a symlink from <filename>/etc/resolv.conf</filename>. This file may be symlinked from
 316       <filename>/etc/resolv.conf</filename> in order to connect all local clients that bypass local DNS APIs
 317       to <command>systemd-resolved</command> with correct search domains settings. This mode of operation is
 318       recommended.</para></listitem>
 319
 320       <listitem><para>A static file <filename>/usr/lib/systemd/resolv.conf</filename> is provided that lists
 321       the 127.0.0.53 DNS stub (see above) as only DNS server. This file may be symlinked from
 322       <filename>/etc/resolv.conf</filename> in order to connect all local clients that bypass local DNS APIs
 323       to <command>systemd-resolved</command>. This file does not contain any search domains.
 324       </para></listitem>
 325
 326       <listitem><para><command>systemd-resolved</command> maintains the
 327       <filename>/run/systemd/resolve/resolv.conf</filename> file for compatibility with traditional Linux
 328       programs. This file may be symlinked from <filename>/etc/resolv.conf</filename> and is always kept
 329       up-to-date, containing information about all known DNS servers. Note the file format's limitations: it
 330       does not know a concept of per-interface DNS servers and hence only contains system-wide DNS server
 331       definitions. Note that <filename>/run/systemd/resolve/resolv.conf</filename> should not be used
 332       directly by applications, but only through a symlink from <filename>/etc/resolv.conf</filename>. If
 333       this mode of operation is used local clients that bypass any local DNS API will also bypass
 334       <command>systemd-resolved</command> and will talk directly to the known DNS servers.</para></listitem>
 335
 336       <listitem><para>Alternatively, <filename>/etc/resolv.conf</filename> may be managed by other packages,
 337       in which case <command>systemd-resolved</command> will read it for DNS configuration data. In this mode
 338       of operation <command>systemd-resolved</command> is consumer rather than provider of this configuration
 339       file. </para></listitem>
 340     </itemizedlist>
 341
 342     <para>Note that the selected mode of operation for this file is detected fully automatically, depending
 343     on whether <filename>/etc/resolv.conf</filename> is a symlink to
 344     <filename>/run/systemd/resolve/resolv.conf</filename> or lists 127.0.0.53 as DNS server.</para>
 345   </refsect1>
 346
 347   <refsect1>
 348     <title>Signals</title>
 349
 350     <variablelist>
 351       <varlistentry>
 352         <term><constant>SIGUSR1</constant></term>
 353
 354         <listitem><para>Upon reception of the <constant>SIGUSR1</constant> process signal
 355         <command>systemd-resolved</command> will dump the contents of all DNS resource record caches it
 356         maintains, as well as all feature level information it learnt about configured DNS servers into the
 357         system logs.</para></listitem>
 358       </varlistentry>
 359
 360       <varlistentry>
 361         <term><constant>SIGUSR2</constant></term>
 362
 363         <listitem><para>Upon reception of the <constant>SIGUSR2</constant> process signal
 364         <command>systemd-resolved</command> will flush all caches it maintains. Note that it should normally
 365         not be necessary to request this explicitly – except for debugging purposes – as
 366         <command>systemd-resolved</command> flushes the caches automatically anyway any time the host's
 367         network configuration changes. Sending this signal to <command>systemd-resolved</command> is
 368         equivalent to the <command>resolvectl flush-caches</command> command, however the latter is
 369         recommended since it operates in a synchronous way.</para></listitem>
 370       </varlistentry>
 371
 372       <varlistentry>
 373         <term><constant>SIGRTMIN+1</constant></term>
 374
 375         <listitem><para>Upon reception of the <constant>SIGRTMIN+1</constant> process signal
 376         <command>systemd-resolved</command> will forget everything it learnt about the configured DNS
 377         servers. Specifically any information about server feature support is flushed out, and the server
 378         feature probing logic is restarted on the next request, starting with the most fully featured
 379         level. Note that it should normally not be necessary to request this explicitly – except for
 380         debugging purposes – as <command>systemd-resolved</command> automatically forgets learnt information
 381         any time the DNS server configuration changes. Sending this signal to
 382         <command>systemd-resolved</command> is equivalent to the <command>resolvectl
 383         reset-server-features</command> command, however the latter is recommended since it operates in a
 384         synchronous way.</para></listitem>
 385       </varlistentry>
 386     </variablelist>
 387   </refsect1>
 388
 389   <refsect1>
 390     <title>See Also</title>
 391     <para>
 392       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 393       <citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 394       <citerefentry><refentrytitle>dnssec-trust-anchors.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 395       <citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 396       <citerefentry><refentrytitle>resolvectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 397       <citerefentry project='man-pages'><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 398       <citerefentry project='man-pages'><refentrytitle>hosts</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 399       <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 400       <citerefentry><refentrytitle>systemd-networkd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 401     </para>
 402   </refsect1>
 403
 404 </refentry>