MirOS Manual: host(1)


host(1)             UNIX Programmer's 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 ...]
     nslookup

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".

     nslookup is only included for compatibility reasons. Do not
     use it, it may be removed in the future.

     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 con-
     sidered top-level domain specifications, e.g., "nl."

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     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. 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 asso-
     ciated 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 vari-
     ants (see below).

     The second argument is optional. It allows you to specify a
     particular server to query.  If you don't specify this argu-
     ment, 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. Multi-
     ple 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 con-
         tents of the "additional information" and "authoritative

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         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 gen-
         erates 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 "any-
         thing 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.

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         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 inten-
         tional, 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 encoun-
         tered 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.

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     -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 vari-
         ous 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 con-
         tacted for zone transfers during zone listings. Nor-
         mally, 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 out-
         put.

     -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.

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         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 char-
         acters 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 out-
         put. 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 cir-
     cumstances.

     -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

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         within the given zone during zone listings, such as some
         glue records. For regular queries, it suppresses the
         printing of the "additional information" and "authorita-
         tive 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 qual-
         ifying 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 con-
         structed 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 vir-
         tual 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

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         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 environ-
     ment 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 sup-
     ported. 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, pro-
               tocol 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)

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     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 will
     be 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)

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     The following types have already been reserved in RFC 1700,
     but are not yet implemented.

     SIG       Security signature

     KEY       Security key

     The IP v6 address architecture and DNS extensions are
     defined in RFC 2373 and RFC 1886.

     AAAA      IP v6 address (address spec with colons)

     The following type is documented in RFC 1876.

     LOC       Geographical location (latitude, longitude, alti-
               tude, 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

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         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 author-
         itative.

     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

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         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 seri-
     ous 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

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         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 charac-
         ters. 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

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         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 suc-
         ceeded, 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.

     zone SOA record at server is not authoritative
         When checking the SOA for a zone at one of its sup-
         posedly authoritative nameservers, the SOA information
         turns out to be not authoritative.  This could be deter-
         mined 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

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         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 prob-
         ably 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 prob-
         ably 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 prob-
         ably 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 prob-
         ably 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 prob-
         ably 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 prob-
         ably 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

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     taking everything after its first dot.

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

     HOSTALIASES
     In addition, the user can supply his own single-word abbre-
     viations for host names. They should be in a file consisting
     of one line per abbreviation. Each line contains an abbrevi-
     ation, whitespace, 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 authorita-
     tive 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 pos-
     sible 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

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     rfc1664, Using DNS to distribute X.400 address mappings
     rfc1700, Assigned numbers
     rfc1706, DNS NSAP resource records
     rfc1712, DNS encoding of geographical location
     rfc1713, Tools for DNS debugging
     rfc1794, DNS support for load balancing
     rfc1876, Expressing location information in the DNS
     rfc1884, IP v6 addressing architecture
     rfc1886, DNS extensions to support IP v6
     rfc1912, Common DNS operational and configuration errors
     rfc1982, Serial number arithmetic
     rfc1995, Incremental zone transfer in DNS
     rfc1996, Prompt notification of zone changes

AUTHOR

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

SEE ALSO

     resolv.conf(5), resolver(3)

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