host

host(1)                     General Commands Manual                    host(1)



NAME
       host - query nameserver about domain names and zones

SYNOPSIS
       host [-v] [-a] [-t querytype] [options]  name  [server]
       host [-v] [-a] [-t querytype] [options]  -l zone  [server]
       host [-v] [options] -H [-D] [-E] [-G] zone
       host [-v] [options] -C zone
       host [-v] [options] -A host

       host [options] -x [name ...]
       host [options] -X server [name ...]

DESCRIPTION
       host looks for information about Internet hosts and domain names.  It
       gets this information from a set of interconnected servers that are
       spread across the world. The information is stored in the form of
       "resource records" belonging to hierarchically organized "zones".

       By default, the program simply converts between host names and Internet
       addresses. However, with the -t, -a and -v options, it can be used to
       find all of the information about domain names that is maintained by
       the domain nameserver system.  The information printed consists of
       various fields of the associated resource records that were retrieved.

       The arguments can be either host names (domain names) or numeric
       Internet addresses.

       A numeric Internet address consists of four decimal numbers separated
       by dots, e.g. 192.16.199.1, representing the four bytes of the 32-bit
       address.
       The default action is to look up the associated host name.

       A host name or domain name consists of component names (labels)
       separated by dots, e.g. nikhefh.nikhef.nl
       The default action is to look up all of its Internet addresses.

       For single names without a trailing dot, the local domain is
       automatically tacked on the end.  Thus a user in domain "nikhef.nl" can
       say "host nikhapo", and it will actually look up "nikhapo.nikhef.nl".
       In all other cases, the name is tried unchanged.  Single names with
       trailing dot are considered top-level domain specifications, e.g. "nl."

       Note that the usual lookup convention for any name that does not end
       with a trailing dot is to try first with the local domain appended, and
       possibly other search domains.  (As of BIND 4.9, names that have
       embedded dots but no trailing dot are first tried ``as is'' before
       appending search domains) This convention is not used by this program.

       The actual suffix to tack on the end is usually the local domain as
       specified in the /etc/resolv.conf file, but this can be overridden.
       See below for a description of how to customize the host name lookup.

ARGUMENTS
       The first argument is normally the host name (domain name) for which
       you want to look up the requested information.  If the first argument
       is an Internet address, a query is done on the special "reverse
       mapping" domain to look up its associated host name.

       If the -l option is given, the first argument is a domain zone name for
       which a complete listing is given. The program enters a special zone
       listing mode which has several variants (see below).

       The second argument is optional. It allows you to specify a particular
       server to query.  If you don't specify this argument, default servers
       are used, as defined by the /etc/resolv.conf file.

   EXTENDED SYNTAX
       If the -x option is given, it extends the syntax in the sense that
       multiple arguments are allowed on the command line. An optional
       explicit server must now be specified using the -X option as it cannot
       be given as an ordinary argument any more. The -X option implies -x.

       The extended syntax allows no arguments at all, in which case the
       arguments will be read from standard input. This can be a pipe,
       redirection from a file, or an interactive terminal. Note that these
       arguments are the names to be queried, and not command options.
       Everything that appears after a '#' or ';' on an input line will be
       skipped. Multiple arguments per line are allowed.

   OPTIONS
       There are a number of options that can be used before the specified
       arguments.  Some of these options are meaningful only to the people who
       maintain the domain database zones.  The first options are the
       regularly used ones.

       -v  causes printout to be in a "verbose" format.  All resource record
           fields are printed.  Without this option, the ttl and class fields
           are not shown.  Also the contents of the "additional information"
           and "authoritative nameservers" sections in the answer from the
           nameserver are printed, if present.  Normally these sections are
           not shown.  In addition, the verbose option prints extra
           information about the various actions that are taken by the
           program.  Note that -vv is "very verbose". This generates a lot of
           output.

       -t querytype
           allows you to specify a particular type of resource record
           information to be looked up.  Supported types are listed below.
           The wildcard may be written as either ANY or *.  Types may be given
           in upper or lower case.  The default is type A for regular lookups,
           and A, NS, and PTR for zone listings.

       -a  is equivalent to -t ANY.  Note that this gives you "anything
           available" (currently cached) and not "all defined data" if a non-
           authoritative server is queried.

   SPECIAL MODES
       The following options put the program in a special mode.

       -l zone
           generates the listing of an entire zone.

           E.g. the command
                host -l nikhef.nl
           will give a listing of all hosts in the "nikhef.nl" zone.  The -t
           option is used to filter what information is extracted, as you
           would expect. The default is address information from A records,
           supplemented with data from PTR and NS records.

           The command
                host -Z -a -l nikhef.nl
           will give a complete download of the zone data for "nikhef.nl", in
           the official master file format.

       -H  can be specified instead of the -l option. It will print the count
           of the unique hostnames (names with an A record) encountered within
           the zone.  It will not count pseudo names like "localhost", nor
           addresses associated with the zone name itself. Neither are counted
           the "glue records" that are necessary to define nameservers for the
           zone and its delegated zones.

           By default, this option will not print any resource records.

           Combined with the -S option, it will give a complete statistics
           survey of the zone.

           The host count may be affected by duplicate hosts (see below).  To
           compute the most realistic value, subtract the duplicate host count
           from the total host count.

       -G  implies -H, but lists the names of gateway hosts.  These are the
           hosts that have more than one address.  Gateway hosts are not
           checked for duplicate addresses.

       -E  implies -H, but lists the names of extrazone hosts.  An extrazone
           host in zone "foo.bar" is of the form "host.xxx.foo.bar" where
           "xxx.foo.bar" is not defined as a delegated zone with an NS record.
           This may be intentional, but also may be an error.

       -D  implies -H, but lists the names of duplicate hosts.  These are
           hosts with only one address, which is known to have been defined
           also for another host with a different name, possibly even in a
           different zone.  This may be intentional, but also may be an error.

       -C  can be specified instead of the -l option. It causes the SOA
           records for the specified zone to be compared as found at each of
           the authoritative nameservers for the zone (as listed in the NS
           records).  Nameserver recursion is turned off, and it will be
           checked whether the answers are really authoritative. If a server
           cannot provide an authoritative SOA record, a lame delegation of
           the zone to that server is reported.  Discrepancies between the
           records are reported. Various sanity checks are performed.

       -A  enters a special address check mode.

           If the first argument is a host name, its addresses will be
           retrieved, and for each of the addresses it will be checked whether
           they map back to the given host.

           If the first argument is a dotted quad Internet address, its name
           will be retrieved, and it will be checked whether the given address
           is listed among the known addresses belonging to that host.

           If the -A flag is specified along with any zone listing option, a
           reverse lookup of the address in each encountered A record is
           performed, and it is checked whether it is registered and maps back
           to the name of the A record.

   SPECIAL OPTIONS
       The following options apply only to the special zone listing modes.

       -L level
           Recursively generate zone listings up to this level deep.  Level 1
           traverses the parent zone and all of its delegated zones.  Each
           additional level descends into another layer of delegated zones.

       -S  prints statistics about the various types of resource records found
           during zone listings, the number of various host classifications,
           the number of delegated zones, and some total statistics after
           recursive listings.

       -p  causes only the primary nameserver of a zone to be contacted for
           zone transfers during zone listings. Normally, zone transfers are
           obtained from any one of the authoritative servers that responds.
           The primary nameserver is obtained from the SOA record of the zone.
           If a specific server is given on the command line, this option will
           query that server for the desired nameservers of the zone. This can
           be used for testing purposes in case the zone has not been
           registered yet.

       -P prefserver
           gives priority for zone transfers to preferred servers residing in
           domains given by the comma-separated list prefserver. The more
           domain component labels match, the higher the priority.  If this
           option is not present, priority is given to servers within your own
           domain or parent domains.  The order in which NS records are issued
           may be unfavorable if they are subject to BIND 4.9 round-robin
           reshuffling.

       -N skipzone
           prohibits zone transfers for the zones given by the comma-separated
           list skipzone. This may be used during recursive zone listings when
           certain zones are known to contain bogus information which should
           be excluded from further processing.

   COMMON OPTIONS
       The following options can be used in both normal mode and domain
       listing mode.

       -d  turns on debugging.  Nameserver transactions are shown in detail.
           Note that -dd prints even more debugging output.

       -f filename
           writes the resource record output to the given logfile as well as
           to standard output.

       -F filename
           same as -f, but exchange the role of stdout and logfile.  All
           stdout output (including verbose and debug printout) goes to the
           logfile, and stdout gets only the extra resource record output (so
           that it can be used in pipes).

       -I chars
           suppresses warning messages about illegal domain names containing
           invalid characters, by specifying such characters in the string
           chars. The underscore is a good candidate.

       -i  constructs a query for the "reverse mapping" in-addr.arpa domain in
           case a numeric (dotted quad) address was specified.  Useful
           primarily for zone listing mode, since for numeric regular lookups
           such query is done anyway (but with -i you see the actual PTR
           resource record outcome).

       -n  constructs a query for the "reverse mapping" nsap.int domain in
           case an nsap address was specified.  This can be used to look up
           the names associated with nsap addresses, or to list reverse nsap
           zones.  An nsap address consists of an even number of hexadecimal
           digits, with a maximum of 40, optionally separated by interspersed
           dots.  An optional prefix "0x" is skipped.  If this option is used,
           all reverse nsap.int names are by default printed in forward
           notation, only to improve readability.  The -Z option forces the
           output to be in the official zone file format.

       -q  be quiet and suppress various warning messages (the ones preceded
           by " !!! ").  Serious error messages (preceded by " *** ") are
           never suppressed.

       -T  prints the time-to-live values during non-verbose output.  By
           default the ttl is shown only in verbose mode.

       -Z  prints the selected resource record output in full zone file
           format, including trailing dot in domain names, plus ttl value and
           class name.

   OTHER OPTIONS
       The following options are used only in special circumstances.

       -c class
           allows you to specify a particular resource record class.
           Supported are IN, INTERNET, CS, CSNET, CH, CHAOS, HS, HESIOD, and
           the wildcard ANY or *.  The default class is IN.

       -e  excludes information about names that are not residing within the
           given zone during zone listings, such as some glue records.  For
           regular queries, it suppresses the printing of the "additional
           information" and "authoritative nameserver" sections in the answer
           from the nameserver.

       -m  is equivalent to -t MAILB, which filters any of types MB, MR, MG,
           or MINFO.  In addition, MR and MG records will be recursively
           expanded into MB records.

       -o  suppresses the resource record output to stdout. Can be used in
           combination with the -f option to separate the resource record
           output from verbose and debug comments and error messages.

       -r  causes nameserver recursion to be turned off in the request.  This
           means that the contacted nameserver will return only data it has
           currently cached in its own database.  It will not ask other
           servers to retrieve the information.  Note that nameserver
           recursion is always turned off when checking SOA records using the
           -C option. Authoritative servers should have all relevant
           information available.

       -R  Normally querynames are assumed to be fully qualified and are tried
           as such, unless it is a single name, which is always tried (and
           only once) in the default domain.  This option simulates the
           default BIND behavior by qualifying any specified name by
           repeatedly adding search domains, with the exception that the
           search terminates immediately if the name exists but does not have
           the desired querytype.  The default search domains are constructed
           from the default domain by repeatedly peeling off the first
           component, until a final domain with only one dot remains.

       -s seconds
           specifies a new nameserver timeout value. The program will wait for
           a nameserver reply in two attempts of this number of seconds.
           Normally it does 2 attempts of 5 seconds per nameserver address
           tried.  The actual timeout algorithm is slightly more complicated,
           extending the timeout value dynamically depending on the number of
           tries and the number of nameserver addresses.

       -u  forces the use of virtual circuits (TCP) instead of datagrams (UDP)
           when issuing nameserver queries. This is slower, but potentially
           more reliable.  Note that a virtual circuit is automatically chosen
           in case a query exceeds the maximum datagram packet size. Also if a
           datagram answer turns out to be truncated, the query is retried
           using virtual circuit.  A zone transfer is always done via a
           virtual circuit.

       -w  causes the program to retry forever if the response to a regular
           query times out. Normally it will time out after some 10 seconds
           per nameserver address tried.

       -V  prints just the version number of the host program, and exits.

   DEFAULT OPTIONS
       Default options and parameters can be preset in an environment variable
       HOST_DEFAULTS using the same syntax as on the command line. They will
       be evaluated before the command line arguments.

QUERYTYPES
       The following querytypes (resource record types) are supported.
       Indicated within parentheses are the various kinds of data fields.

       A         Host address (dotted quad)

       NS        Authoritative nameserver (domain name)

       MD        Mail destination (domain name)

       MF        Mail forwarder (domain name)

       CNAME     Canonical name for an alias (domain name)

       SOA       Marks the start of a zone of authority (domain name of
                 primary, domain name of hostmaster, serial, refresh, retry,
                 expiration, default ttl)

       MB        Mailbox domain name (domain name)

       MG        Mail group member (domain name)

       MR        Mail rename domain name (domain name)

       NULL      Null resource record (no format or data)

       WKS       Well-known service description (dotted quad, protocol name,
                 list of services)

       PTR       Domain name pointer (domain name)

       HINFO     Host information (CPU type string, OS type string)

       MINFO     Mailbox or mail list information (request domain name, error
                 domain name)

       MX        Mail exchanger (preference value, domain name)

       TXT       Descriptive text (one or more strings)

       UINFO     User information (string)

       UID       User identification (number)

       GID       Group identification (number)

       UNSPEC    Unspecified binary data (data)

       ANY       Matches information of any type available.

       MAILB     Matches any of types MB, MR, MG, or MINFO.

       MAILA     Matches any of types MD, or MF.

       The following types have been defined in RFC 1183, but are not yet in
       general use. They are recognized by this program.

       RP        Responsible person (domain name for MB, domain name for TXT)

       AFSDB     AFS database location (type, domain name)

       X25       X25 address (address string)

       ISDN      ISDN address (address string, optional subaddress string)

       RT        Route through host (preference value, domain name)

       The following types have been defined in RFC 1348, but are not yet in
       general use. They are recognized by this program.  RFC 1348 has already
       been obsoleted by RFC 1637 and RFC 1706, which defines a new
       experimental usage of NSAP records.  This program has now hooks to
       manipulate them.

       NSAP      NSAP address (encoded address)

       NSAP-PTR  NSAP pointer (domain name)

       The following are new types as per RFC 1664 and RFC 1712.  Note that
       the GPOS type has been withdrawn already, and has been superseded by
       the LOC type.

       PX        X400 to RFC822 mapping (preference value, rfc822 domain, x400
                 domain)

       GPOS      Geographical position (longitude string, latitude string,
                 altitude string)

       The following types have been reserved in RFC 1700, and are defined in
       RFC 2065.

       SIG       Security signature

       KEY       Security key

       The IP v6 address architecture and DNS extensions are defined in RFC
       1884 and RFC 1886.

       AAAA      IP v6 address (address spec with colons)

       The following type is documented in RFC 1876.

       LOC       Geographical location (latitude, longitude, altitude,
                 precision)

       The following types have been proposed, but are still in draft.

       NXT       Next valid record

       EID       Endpoint identifier

       NIMLOC    Nimrod locator

       SRV       Internet service information

       ATMA      ATM address

       NAPTR     Naming authority URN

EXAMPLES
       A very good summary and validation of an entire zone can be obtained
       with the following command:

            host -G -S -C -A -L 1 zone


DIAGNOSTICS
   FAILURE MESSAGES
       The following messages are printed to show the reason of failure for a
       particular query. The name of an explicit server, if specified, may be
       included. If a special class was requested, it is also shown.

       Nameserver [server] not running
           The contacted server host does not have a nameserver running.

       Nameserver [server] not responding
           The nameserver at the contacted server host did not give a reply
           within the specified time frame.

       Nameserver [server] not reachable
           The network route to the intended server host is blocked.

       name does not exist [at server] (Authoritative answer)
           The queryname does definitely not exist at all.

       name does not exist [at server], try again
           The queryname does not exist, but the answer was not authoritative,
           so it is still undecided.

       name has no type record [at server] (Authoritative answer)
           The queryname is valid, but the specified type does not exist.
           This status is here returned only in case authoritative.

       name type record currently not present [at server]
           The specified type does not exist, but we don't know whether the
           queryname is valid or not. The answer was not authoritative.
           Perhaps recursion was off, and no data was cached locally.

       name type record not found [at server], try again
           Some intermediate failure, e.g. timeout reaching a nameserver.

       name type record not found [at server], server failure
           Some explicit nameserver failure to process the query, due to
           internal or forwarding errors. This may also be returned if the
           zone data has expired at a secondary server, of when the server is
           not authoritative for some class.

       name type record not found [at server], no recovery
           Some irrecoverable format error, or server refusal.

       name type record query refused [by server]
           The contacted nameserver explicitly refused to answer the query.
           Some nameservers are configured to refuse zone transfer requests
           that come from arbitrary clients.

       name type record not found [at server]
           The exact reason for failure could not be determined.  (This should
           not happen).

       zone has lame delegation to server
           If we query a supposedly authoritative nameserver for the SOA
           record of a zone, the information should be available and the
           answer should be authoritative. If not, a lame delegation is
           flagged. This is also done if the server turns out not to exist at
           all. Ditto if we ask for a zone transfer and the server cannot
           provide it.

       No nameservers for zone found
           It was not possible to retrieve the name of any nameserver for the
           desired zone, in order to do a zone transfer.

       No addresses of nameservers for zone found
           We got some nameserver names, but it was not possible to retrieve
           addresses for any of them.

       No nameservers for zone responded
           When trying all nameservers in succession to do a zone transfer,
           none of them were able or willing to provide it.

   WARNING AND ERROR MESSAGES
       Miscellaneous warning messages may be generated.  They are preceded by
       " !!! " and indicate some non-fatal condition, usually during the
       interpretation of the retrieved data.  These messages can be suppressed
       with the -q command line option.

       Error messages are preceded by " *** " and indicate a serious problem,
       such as format errors in the answers to queries, but also major
       violations of the specifications.  Those messages cannot be suppressed.

       zone has only one nameserver server
           When retrieving the nameservers for a zone, it appears that only
           one single nameserver exists.  This is against the recommendations.

       zone nameserver server is not canonical (realserver)
           When retrieving the nameservers for a zone, the name of the
           specified server appears not to be canonical. This may cause
           serious operational problems. The canonical name is given between
           parentheses.

       empty zone transfer for zone from server
           The zone transfer from the specified server contained no data,
           perhaps only the SOA record. This could happen if we query the
           victim of a lame delegation which happens to have the SOA record in
           its cache.

       extraneous NS record for name within zone from server
           During a zone transfer, an NS record appears for a name which is
           not a delegated subzone of the current zone.

       extraneous SOA record for name within zone from server
           During a zone transfer, an SOA record appears for a name which is
           not the name of the current zone.

       extraneous glue record for name within zone from server
           During a zone transfer, a glue record is included for a name which
           is not part of the zone or its delegated subzones. This is done in
           some older versions of BIND. It is undesirable since
           unauthoritative, or even incorrect, information may be propagated.

       incomplete type record for name
           When decoding the resource record data from the answer to a query,
           not all required data fields were present. This is frequently the
           case for HINFO records of which only one of the two data field is
           encoded.

       name has both NS and A records within zone from server
           An A record has been defined for the delegated zone name. This is
           signalled only during the transfer of the parent zone. It is not an
           error, but the overall hostcount may be wrong, since the A record
           is counted as a host in the parent zone. This A record is not
           included in the hostcount of the delegated zone.

       name type records have different ttl within zone from server
           Resource records of the same name/type/class should have the same
           ttl value in zone listings. This is sometimes not the case, due to
           the independent definition of glue records or other information in
           the parent zone, which is not kept in sync with the definition in
           the delegated zone.

       name type record has illegal name
           The name of an A or MX record contains invalid characters.  Only
           alphanumeric characters and hyphen '-' are valid in components
           (labels) between dots.

       name type host server has illegal name
           The name of an NS or MX target host contains invalid characters.
           Only alphanumeric characters and hyphen '-' are valid in components
           (labels) between dots.

       name type host server does not exist
           The NS or MX target host server does not exist at all.  In case of
           NS, a lame delegation of name to server is flagged.

       name type host server has no A record
           The NS or MX target host server has no address.  In case of NS, a
           lame delegation of name to server is flagged.

       name type host server is not canonical
           The NS or MX target host server is not a canonical name.  This may
           cause serious operational problems during domain data retrieval, or
           electronic mail delivery.

       name address A.B.C.D is not registered
           The reverse lookup of the address of an A record failed in an
           authoritative fashion. It was not present in the corresponding in-
           addr.arpa zone.

       name address A.B.C.D maps to realname
           The reverse lookup of the address of an A record succeeded, but it
           did not map back to the name of the A record.  There may be A
           records with different names for the same address.  In the reverse
           in-addr.arpa zone there is usually only one PTR to the ``official''
           host name.

       name address A.B.C.D maps to alias aliasname
           In case of multiple PTR records, the first one encountered points
           to the ``official'' host name. Subsequent ones are returned as
           alias names via gethostbyaddr() as of BIND 4.9. Note that PTR
           records are exempt from round-robin reshuffling.

       zone SOA record at server is not authoritative
           When checking the SOA for a zone at one of its supposedly
           authoritative nameservers, the SOA information turns out to be not
           authoritative.  This could be determined by making a query without
           nameserver recursion turned on.

       zone SOA primary server is not advertised via NS
           The primary nameserver is not among the list of nameservers
           retrieved via NS records for the zone.  This is not an error per
           se, since only publicly accessible nameservers may be advertised,
           and others may be behind a firewall.

       zone SOA primary server has illegal name
           The name of the primary nameserver contains invalid characters.

       zone SOA hostmaster mailbox has illegal mailbox
           The name of the hostmaster mailbox contains invalid characters.  A
           common mistake is to use an RFC822 email address with a ``@'',
           whereas the at-sign should have been replaced with a dot.

       zone SOA serial has high bit set
           Although the serial number is an unsigned 32-bit value, overflow
           into the high bit can inadvertently occur by making inappropriate
           use of the dotted decimal notation in the zone file. This may lead
           to synchronization failures between primary and secondary servers.

       zone SOA retry exceeds refresh
           A failing refresh would be retried after it is time for the next
           refresh.

       zone SOA refresh+retry exceeds expire
           The retry after a failing refresh would be done after the data has
           already expired.

       server1 and server2 have different primary for zone
           If the SOA record is different, the zone data is probably different
           as well. What you get depends on which server you happen to query.

       server1 and server2 have different hostmaster for zone
           If the SOA record is different, the zone data is probably different
           as well. What you get depends on which server you happen to query.

       server1 and server2 have different serial for zone
           This is usually not an error, but happens during the period after
           the primary server has updated its zone data, but before a
           secondary performed a refresh. Nevertheless there could be an error
           if a mistake has been made in properly adapting the serial number.

       server1 and server2 have different refresh for zone
           If the SOA record is different, the zone data is probably different
           as well. What you get depends on which server you happen to query.

       server1 and server2 have different retry for zone
           If the SOA record is different, the zone data is probably different
           as well. What you get depends on which server you happen to query.

       server1 and server2 have different expire for zone
           If the SOA record is different, the zone data is probably different
           as well. What you get depends on which server you happen to query.

       server1 and server2 have different defttl for zone
           If the SOA record is different, the zone data is probably different
           as well. What you get depends on which server you happen to query.

EXIT STATUS
       The program returns a zero exit status if the requested information
       could be retrieved successfully, or in case zone listings or SOA checks
       were performed without any serious error.  Otherwise it returns a non-
       zero exit status.

ENVIRONMENT
   CUSTOMIZING HOST NAME LOOKUP
       In general, if the name supplied by the user does not have any dots in
       it, a default domain is appended to the end. This domain is usually
       defined in the /etc/resolv.conf file. If not, it is derived by taking
       the local hostname and taking everything after its first dot.

       The user can override this, and specify a different default domain, by
       defining it in the environment variable LOCALDOMAIN.

       In addition, the user can supply his own single-word abbreviations for
       host names. They should be in a file consisting of one line per
       abbreviation. Each line contains an abbreviation, white space, and then
       the fully qualified host name. The name of this file must be specified
       in the environment variable HOSTALIASES.

SPECIAL CONSIDERATIONS
       The complete set of resource record information for a domain name is
       available from an authoritative nameserver only. Therefore, if you
       query another server with the "-a" option, only a subset of the data
       may be presented, since this option asks for any data that the latter
       server currently knows about, not all data that may possibly exist.
       Note that the "-v" option shows whether an answer is authoritative or
       not.

       When listing a zone with the "-l" option, information will be fetched
       from authoritative nameservers for that zone. This is implemented by
       doing a complete zone transfer and then filtering out the information
       that you have asked for.  Note that direct contact with such
       nameservers must be possible for this option to work.  This option
       should be used with caution. Servers may be configured to refuse zone
       transfers if they are flooded with requests.

RELATED DOCUMENTATION
       rfc883, Domain names - implementation and specification
       rfc920, Domain requirements
       rfc952, DOD Internet host table specification
       rfc974, Mail routing and the domain system
       rfc1032, Domain administrators guide
       rfc1033, Domain administrators operations guide
       rfc1034, Domain names - concepts and facilities
       rfc1035, Domain names - implementation and specification
       rfc1101, DNS encoding of network names and other types
       rfc1123, Requirements for Internet hosts - application
       rfc1183, New DNS RR definitions
       rfc1348, DNS NSAP RRs
       rfc1535, A security problem and proposed correction
       rfc1536, Common DNS implementation errors
       rfc1537, Common DNS data file configuration errors
       rfc1591, Domain Name System structure and delegation
       rfc1637, DNS NSAP resource records
       rfc1664, Using DNS to distribute X.400 address mappings
       rfc1700, Assigned numbers
       rfc1706, DNS NSAP resource records
       rfc1712, DNS encoding of geographical location (GPOS)
       rfc1713, Tools for DNS debugging
       rfc1794, DNS support for load balancing
       rfc1876, Expressing location information in the DNS (LOC)
       rfc1884, IP v6 addressing architecture
       rfc1886, DNS extensions to support IP v6 (AAAA)
       rfc1912, Common DNS operational and configuration errors
       rfc1982, Serial number arithmetic
       rfc1995, Incremental zone transfer in DNS (IXFR)
       rfc1996, Prompt notification of zone changes
       rfc2010, Operational criteria for root nameservers
       rfc2052, Specification of location of services (SRV)
       rfc2065, DNS security extensions (KEY/SIG/NXT)

AUTHOR
       This program is originally from Rutgers University.
       Rewritten by Eric Wassenaar, NIKHEF, <e07@nikhef.nl>

SEE ALSO
       named(8), resolv.conf(5), resolver(3)



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