Ubuntu Manpage: resolvectl, resolvconf - Resolve domain names, IPV4 and IPv6 addresses, DNS resource

Provided by: systemd_249.11-0ubuntu3.12_amd64

NAME

       resolvectl, resolvconf - Resolve domain names, IPV4 and IPv6 addresses, DNS resource
       records, and services; introspect and reconfigure the DNS resolver

SYNOPSIS

       resolvectl [OPTIONS...] {COMMAND} [NAME...]

DESCRIPTION

       resolvectl may be used to resolve domain names, IPv4 and IPv6 addresses, DNS resource
       records and services with the systemd-resolved.service(8) resolver service. By default,
       the specified list of parameters will be resolved as hostnames, retrieving their IPv4 and
       IPv6 addresses. If the parameters specified are formatted as IPv4 or IPv6 operation the
       reverse operation is done, and a hostname is retrieved for the specified addresses.

       The program's output contains information about the protocol used for the look-up and on
       which network interface the data was discovered. It also contains information on whether
       the information could be authenticated. All data for which local DNSSEC validation
       succeeds is considered authenticated. Moreover all data originating from local, trusted
       sources is also reported authenticated, including resolution of the local host name, the
       "localhost" hostname or all data from /etc/hosts.

COMMANDS

query HOSTNAME|ADDRESS...
Resolve domain names, as well as IPv4 and IPv6 addresses. When used in conjunction
with --type= or --class= (see below), resolves low-level DNS resource records.

If a single-label domain name is specified it is searched for according to the
configured search domains — unless --search=no or --type=/--class= are specified, both
of which turn this logic off.

If an international domain name is specified, it is automatically translated according
to IDNA rules when resolved via classic DNS — but not for look-ups via MulticastDNS or
LLMNR. If --type=/--class= is used IDNA translation is turned off and domain names are
processed as specified.

service [[NAME] TYPE] DOMAIN
Resolve DNS-SD[1] and SRV[2] services, depending on the specified list of parameters.
If three parameters are passed the first is assumed to be the DNS-SD service name, the
second the SRV service type, and the third the domain to search in. In this case a
full DNS-SD style SRV and TXT lookup is executed. If only two parameters are
specified, the first is assumed to be the SRV service type, and the second the domain
to look in. In this case no TXT resource record is requested. Finally, if only one
parameter is specified, it is assumed to be a domain name, that is already prefixed
with an SRV type, and an SRV lookup is done (no TXT).

openpgp EMAIL@DOMAIN...
Query PGP keys stored as OPENPGPKEY resource records, see RFC 7929[3]. Specified
e-mail addresses are converted to the corresponding DNS domain name, and any
OPENPGPKEY keys are printed.

tlsa [FAMILY] DOMAIN[:PORT]...
Query TLS public keys stored as TLSA resource records, see RFC 6698[4]. A query will
be performed for each of the specified names prefixed with the port and family
("_port._family.domain"). The port number may be specified after a colon (":"),
otherwise 443 will be used by default. The family may be specified as the first
argument, otherwise tcp will be used.

status [LINK...]
Shows the global and per-link DNS settings currently in effect. If no command is
specified, this is the implied default.

statistics
Shows general resolver statistics, including information whether DNSSEC is enabled and
available, as well as resolution and validation statistics.

reset-statistics
Resets the statistics counters shown in statistics to zero. This operation requires
root privileges.

flush-caches
Flushes all DNS resource record caches the service maintains locally. This is mostly
equivalent to sending the SIGUSR2 to the systemd-resolved service.

reset-server-features
Flushes all feature level information the resolver learnt about specific servers, and
ensures that the server feature probing logic is started from the beginning with the
next look-up request. This is mostly equivalent to sending the SIGRTMIN+1 to the
systemd-resolved service.

dns [LINK [SERVER...]], domain [LINK [DOMAIN...]], default-route [LINK [BOOL...]], llmnr
[LINK [MODE]], mdns [LINK [MODE]], dnssec [LINK [MODE]], dnsovertls [LINK [MODE]], nta
[LINK [DOMAIN...]]
Get/set per-interface DNS configuration. These commands may be used to configure
various DNS settings for network interfaces. These commands may be used to inform
systemd-resolved or systemd-networkd about per-interface DNS configuration determined
through external means. The dns command expects IPv4 or IPv6 address specifications of
DNS servers to use. Each address can optionally take a port number separated with ":",
a network interface name or index separated with "%", and a Server Name Indication
(SNI) separated with "#". 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
"111.222.333.444:9953%ifname#example.com" for IPv4 and
"[1111:2222::3333]:9953%ifname#example.com" for IPv6. The domain command expects valid
DNS domains, possibly prefixed with "~", and configures a per-interface search or
route-only domain. The default-route command expects a boolean parameter, and
configures whether the link may be used as default route for DNS lookups, i.e. if it
is suitable for lookups on domains no other link explicitly is configured for. The
llmnr, mdns, dnssec and dnsovertls commands may be used to configure the per-interface
LLMNR, MulticastDNS, DNSSEC and DNSOverTLS settings. Finally, nta command may be used
to configure additional per-interface DNSSEC NTA domains.

Commands dns, domain and nta can take a single empty string argument to clear their
respective value lists.

For details about these settings, their possible values and their effect, see the
corresponding settings in systemd.network(5).

revert LINK
Revert the per-interface DNS configuration. If the DNS configuration is reverted all
per-interface DNS setting are reset to their defaults, undoing all effects of dns,
domain, default-route, llmnr, mdns, dnssec, dnsovertls, nta. Note that when a network
interface disappears all configuration is lost automatically, an explicit reverting is
not necessary in that case.

log-level [LEVEL]
If no argument is given, print the current log level of the manager. If an optional
argument LEVEL is provided, then the command changes the current log level of the
manager to LEVEL (accepts the same values as --log-level= described in systemd(1)).

OPTIONS

-4, -6
By default, when resolving a hostname, both IPv4 and IPv6 addresses are acquired. By
specifying -4 only IPv4 addresses are requested, by specifying -6 only IPv6 addresses
are requested.

-i INTERFACE, --interface=INTERFACE
Specifies the network interface to execute the query on. This may either be specified
as numeric interface index or as network interface string (e.g. "en0"). Note that
this option has no effect if system-wide DNS configuration (as configured in
/etc/resolv.conf or /etc/systemd/resolved.conf) in place of per-link configuration is
used.

-p PROTOCOL, --protocol=PROTOCOL
Specifies the network protocol for the query. May be one of "dns" (i.e. classic
unicast DNS), "llmnr" (Link-Local Multicast Name Resolution[5]), "llmnr-ipv4",
"llmnr-ipv6" (LLMNR via the indicated underlying IP protocols), "mdns" (Multicast
DNS[6]), "mdns-ipv4", "mdns-ipv6" (MDNS via the indicated underlying IP protocols). By
default the lookup is done via all protocols suitable for the lookup. If used, limits
the set of protocols that may be used. Use this option multiple times to enable
resolving via multiple protocols at the same time. The setting "llmnr" is identical to
specifying this switch once with "llmnr-ipv4" and once via "llmnr-ipv6". Note that
this option does not force the service to resolve the operation with the specified
protocol, as that might require a suitable network interface and configuration. The
special value "help" may be used to list known values.

-t TYPE, --type=TYPE, -c CLASS, --class=CLASS
When used in conjunction with the query command, specifies the DNS resource record
type (e.g. A, AAAA, MX, ...) and class (e.g. IN, ANY, ...) to look up. If these
options are used a DNS resource record set matching the specified class and type is
requested. The class defaults to IN if only a type is specified. The special value
"help" may be used to list known values.

Without these options resolvectl query provides high-level domain name to address and
address to domain name resolution. With these options it provides low-level DNS
resource record resolution. The search domain logic is automatically turned off when
these options are used, i.e. specified domain names need to be fully qualified domain
names. Moreover, IDNA internal domain name translation is turned off as well, i.e.
international domain names should be specified in "xn--..." notation, unless look-up
in MulticastDNS/LLMNR is desired, in which case UTF-8 characters should be used.

--service-address=BOOL
Takes a boolean parameter. If true (the default), when doing a service lookup with
--service the hostnames contained in the SRV resource records are resolved as well.

--service-txt=BOOL
Takes a boolean parameter. If true (the default), when doing a DNS-SD service lookup
with --service the TXT service metadata record is resolved as well.

--cname=BOOL
Takes a boolean parameter. If true (the default), DNS CNAME or DNAME redirections are
followed. Otherwise, if a CNAME or DNAME record is encountered while resolving, an
error is returned.

--validate=BOOL
Takes a boolean parameter; used in conjunction with query. If true (the default),
DNSSEC validation is applied as usual — under the condition that it is enabled for the
network and for systemd-resolved.service as a whole. If false, DNSSEC validation is
disabled for the specific query, regardless of whether it is enabled for the network
or in the service. Note that setting this option to true does not force DNSSEC
validation on systems/networks where DNSSEC is turned off. This option is only
suitable to turn off such validation where otherwise enabled, not enable validation
where otherwise disabled.

--synthesize=BOOL
Takes a boolean parameter; used in conjunction with query. If true (the default),
select domains are resolved on the local system, among them "localhost", "_gateway"
and "_outbound", or entries from /etc/hosts. If false these domains are not resolved
locally, and either fail (in case of "localhost", "_gateway" or "_outbound" and
suchlike) or go to the network via regular DNS/mDNS/LLMNR lookups (in case of
/etc/hosts entries).

--cache=BOOL
Takes a boolean parameter; used in conjunction with query. If true (the default),
lookups use the local DNS resource record cache. If false, lookups are routed to the
network instead, regardless if already available in the local cache.

--zone=BOOL
Takes a boolean parameter; used in conjunction with query. If true (the default),
lookups are answered from locally registered LLMNR or mDNS resource records, if
defined. If false, locally registered LLMNR/mDNS records are not considered for the
lookup request.

--trust-anchor=BOOL
Takes a boolean parameter; used in conjunction with query. If true (the default),
lookups for DS and DNSKEY are answered from the local DNSSEC trust anchors if
possible. If false, the local trust store is not considered for the lookup request.

--network=BOOL
Takes a boolean parameter; used in conjunction with query. If true (the default),
lookups are answered via DNS, LLMNR or mDNS network requests if they cannot be
synthesized locally, or be answered from the local cache, zone or trust anchors (see
above). If false, the request is not answered from the network and will thus fail if
none of the indicated sources can answer them.

--search=BOOL
Takes a boolean parameter. If true (the default), any specified single-label hostnames
will be searched in the domains configured in the search domain list, if it is
non-empty. Otherwise, the search domain logic is disabled. Note that this option has
no effect if --type= is used (see above), in which case the search domain logic is
unconditionally turned off.

--raw[=payload|packet]
Dump the answer as binary data. If there is no argument or if the argument is
"payload", the payload of the packet is exported. If the argument is "packet", the
whole packet is dumped in wire format, prefixed by length specified as a little-endian
64-bit number. This format allows multiple packets to be dumped and unambiguously
parsed.

--legend=BOOL
Takes a boolean parameter. If true (the default), column headers and meta information
about the query response are shown. Otherwise, this output is suppressed.

-h, --help
Print a short help text and exit.

--version
Print a short version string and exit.

--no-pager
Do not pipe output into a pager.

COMPATIBILITY WITH RESOLVCONF(8)

resolvectl is a multi-call binary. When invoked as "resolvconf" (generally achieved by
means of a symbolic link of this name to the resolvectl binary) it is run in a limited
resolvconf(8) compatibility mode. It accepts mostly the same arguments and pushes all data
into systemd-resolved.service(8), similar to how dns and domain commands operate. Note
that systemd-resolved.service is the only supported backend, which is different from other
implementations of this command.

/etc/resolv.conf will only be updated with servers added with this command when
/etc/resolv.conf is a symlink to /run/systemd/resolve/resolv.conf, and not a static file.
See the discussion of /etc/resolv.conf handling in systemd-resolved.service(8).

Not all operations supported by other implementations are supported natively.
Specifically:

-a
Registers per-interface DNS configuration data with systemd-resolved. Expects a
network interface name as only command line argument. Reads resolv.conf(5)-compatible
DNS configuration data from its standard input. Relevant fields are "nameserver" and
"domain"/"search". This command is mostly identical to invoking resolvectl with a
combination of dns and domain commands.

-d
Unregisters per-interface DNS configuration data with systemd-resolved. This command
is mostly identical to invoking resolvectl revert.

-f
When specified -a and -d will not complain about missing network interfaces and will
silently execute no operation in that case.

-x
This switch for "exclusive" operation is supported only partially. It is mapped to an
additional configured search domain of "~." — i.e. ensures that DNS traffic is
preferably routed to the DNS servers on this interface, unless there are other, more
specific domains configured on other interfaces.

-m, -p
These switches are not supported and are silently ignored.

-u, -I, -i, -l, -R, -r, -v, -V, --enable-updates, --disable-updates, --are-updates-enabled
These switches are not supported and the command will fail if used.

See resolvconf(8) for details on those command line options.

EXAMPLES

       Example 1. Retrieve the addresses of the "www.0pointer.net" domain (A and AAAA resource
       records)

           $ resolvectl query www.0pointer.net
           www.0pointer.net: 2a01:238:43ed:c300:10c3:bcf3:3266:da74
                             85.214.157.71

           -- Information acquired via protocol DNS in 611.6ms.
           -- Data is authenticated: no

       Example 2. Retrieve the domain of the "85.214.157.71" IP address (PTR resource record)

           $ resolvectl query 85.214.157.71
           85.214.157.71: gardel.0pointer.net

           -- Information acquired via protocol DNS in 1.2997s.
           -- Data is authenticated: no

       Example 3. Retrieve the MX record of the "yahoo.com" domain

           $ resolvectl --legend=no -t MX query yahoo.com
           yahoo.com. IN MX    1 mta7.am0.yahoodns.net
           yahoo.com. IN MX    1 mta6.am0.yahoodns.net
           yahoo.com. IN MX    1 mta5.am0.yahoodns.net

       Example 4. Resolve an SRV service

           $ resolvectl service _xmpp-server._tcp gmail.com
           _xmpp-server._tcp/gmail.com: alt1.xmpp-server.l.google.com:5269 [priority=20, weight=0]
                                        173.194.210.125
                                        alt4.xmpp-server.l.google.com:5269 [priority=20, weight=0]
                                        173.194.65.125
                                        ...

       Example 5. Retrieve a PGP key (OPENPGP resource record)

           $ resolvectl openpgp zbyszek@fedoraproject.org
           d08ee310438ca124a6149ea5cc21b6313b390dce485576eff96f8722._openpgpkey.fedoraproject.org. IN OPENPGPKEY
                   mQINBFBHPMsBEACeInGYJCb+7TurKfb6wGyTottCDtiSJB310i37/6ZYoeIay/5soJjlMyf
                   MFQ9T2XNT/0LM6gTa0MpC1st9LnzYTMsT6tzRly1D1UbVI6xw0g0vE5y2Cjk3xUwAynCsSs
                   ...

       Example 6. Retrieve a TLS key (TLSA resource record)

           $ resolvectl tlsa tcp fedoraproject.org:443
           _443._tcp.fedoraproject.org IN TLSA 0 0 1 19400be5b7a31fb733917700789d2f0a2471c0c9d506c0e504c06c16d7cb17c0
                   -- Cert. usage: CA constraint
                   -- Selector: Full Certificate
                   -- Matching type: SHA-256

       "tcp" and ":443" are optional and could be skipped.

NOTES

        1. DNS-SD
           https://tools.ietf.org/html/rfc6763

        2. SRV
           https://tools.ietf.org/html/rfc2782

        3. RFC 7929
           https://tools.ietf.org/html/rfc7929

        4. RFC 6698
           https://tools.ietf.org/html/rfc6698

        5. Link-Local Multicast Name Resolution
           https://tools.ietf.org/html/rfc4795

        6. Multicast DNS
           https://www.ietf.org/rfc/rfc6762.txt