systemd-resolve(1)
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). 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
unambigously 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.
--status
Shows the global and per-link DNS settings in currently in effect.
-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
SEE ALSO
systemd(1), systemd-resolved.service(8)
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
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
