Ubuntu Manpage: systemd-resolve - Resolve domain names, IPV4 and IPv6 addresses, DNS resource records, and services

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Provided by: systemd_237-3ubuntu10.57_amd64

NAME

       systemd-resolve - Resolve domain names, IPV4 and IPv6 addresses, DNS resource records, and services

SYNOPSIS

       systemd-resolve [OPTIONS...] HOSTNAME...

       systemd-resolve [OPTIONS...] ADDRESS...

       systemd-resolve [OPTIONS...] --type=TYPE DOMAIN...

       systemd-resolve [OPTIONS...] --service [[NAME] TYPE] DOMAIN

       systemd-resolve [OPTIONS...] --openpgp USER@DOMAIN

       systemd-resolve [OPTIONS...] --tlsa DOMAIN[:PORT]

       systemd-resolve [OPTIONS...] --statistics

       systemd-resolve [OPTIONS...] --reset-statistics

DESCRIPTION

systemd-resolve 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" host name or all data from /etc/hosts.

The --type= switch may be used to specify a DNS resource record type (A, AAAA, SOA, MX, ...) in order to
request a specific DNS resource record, instead of the address or reverse address lookups. The special
value "help" may be used to list known values.

The --service switch may be used to resolve SRV[1] and DNS-SD[2] services (see below). In this mode,
between one and three arguments are required. 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 RR 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).

The --openpgp switch may be used to query PGP keys stored as OPENPGPKEY[3] resource records. When this
option is specified one or more e-mail address must be specified.

The --tlsa switch maybe be used to query TLS public keys stored as TLSA[4] resource records. When this
option is specified one or more domain names must be specified.

The --statistics switch may be used to show resolver statistics, including information about the number
of successful and failed DNSSEC validations.

The --reset-statistics may be used to reset various statistics counters maintained the resolver,
including those shown in the --statistics output. This operation requires root privileges.

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/resolve.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
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.

--service
Enables service resolution. This enables DNS-SD and simple SRV service resolution, depending on the
specified list of parameters (see above).

--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.

--openpgp
Enables OPENPGPKEY resource record resolution (see above). Specified e-mail addresses are converted
to the corresponding DNS domain name, and any OPENPGPKEY keys are printed.

--tlsa
Enables TLSA resource record resolution (see above). 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
an argument after --tlsa, otherwise tcp will be used.

--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.

--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.

--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.

--statistics
If specified general resolver statistics are shown, 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.

--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.

--status
Shows the global and per-link DNS settings in currently in effect.

--set-dns=SERVER, --set-domain=DOMAIN, --set-llmnr=MODE, --set-mdns=MODE, --set-dnssec=MODE,
--set-nta=DOMAIN
Set per-interface DNS configuration. These switches may be used to configure various DNS settings for
network interfaces that aren't managed by systemd-networkd.service(8). (These commands will fail when
used on interfaces that are managed by systemd-networkd, please configure their DNS settings directly
inside the .network files instead.) These switches may be used to inform systemd-resolved about
per-interface DNS configuration determined through external means. Multiple of these switches may be
passed on a single invocation of systemd-resolve in order to set multiple configuration options at
once. If any of these switches is used, it must be combined with --interface= to indicate the network
interface the new DNS configuration belongs to. The --set-dns= option expects an IPv4 or IPv6 address
specification of a DNS server to use, and may be used multiple times to define multiple servers for
the same interface. The --set-domain= option expects a valid DNS domain, possibly prefixed with "~",
and configures a per-interface search or route-only domain. It may be used multiple times to
configure multiple such domains. The --set-llmnr=, --set-mdns= and --set-dnssec= options may be used
to configure the per-interface LLMNR, MulticastDNS and DNSSEC settings. Finally, --set-nta= may be
used to configure additional per-interface DNSSEC NTA domains and may also be used multiple times.
For details about these settings, their possible values and their effect, see the corresponding
options in systemd.network(5).

--revert
Revert the per-interface DNS configuration. This option must be combined with --interface= to
indicate the network interface the DNS configuration shall be reverted on. If the DNS configuration
is reverted all per-interface DNS setting are reset to their defaults, undoing all effects of
--set-dns=, --set-domain=, --set-llmnr=, --set-mdns=, --set-dnssec=, --set-nta=. Note that when a
network interface disappears all configuration is lost automatically, an explicit reverting is not
necessary in that case.

-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.

EXAMPLES

       Example 1. Retrieve the addresses of the "www.0pointer.net" domain

           $ systemd-resolve 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

           $ systemd-resolve 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

           $ systemd-resolve -t MX yahoo.com --legend=no
           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

           $ systemd-resolve --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

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

       Example 6. Retrieve a TLS key ("=tcp" and ":443" could be skipped)

           $ systemd-resolve --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

NOTES

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

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

        3. OPENPGPKEY
           https://tools.ietf.org/html/rfc7929

        4. TLSA
           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