host(1)                                                   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 intercon-
       nected 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 name-
       server system.  The information printed consists of vari-
       ous 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 num-
       bers 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.
       This convention is not used by this program.

       The actual suffix to tack on the end is usually the local



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host(1)                                                   host(1)


       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 pro-
       gram 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. Mul-
       tiple 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 ver-
           bose 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.





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host(1)                                                   host(1)


       -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 informa-
           tion 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.



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host(1)                                                   host(1)


       -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 dif-
           ferent 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 list-
           ing 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 list-
       ing 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 var-
           ious host classifications, the number of delegated



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host(1)                                                   host(1)


           zones, and some total statistics after recursive list-
           ings.

       -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 regis-
           tered 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 pre-
           sent, 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 sub-
           ject 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 log-
           file.  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



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host(1)                                                   host(1)


           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 dig-
           its, 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 out-
           put 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 circum-
       stances.

       -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.




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host(1)                                                   host(1)


       -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 com-
           ments 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 recur-
           sion 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 behav-
           ior 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 trans-
           fer 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



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host(1)                                                   host(1)


       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 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,
                 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)




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host(1)                                                   host(1)


       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 pro-
       gram.

       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 subad-
                 dress 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 pro-
       gram.  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, lati-
                 tude string, altitude string)

       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 1884 and RFC 1886.

       AAAA      IP v6 address (address spec with colons)



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host(1)                                                   host(1)


       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.





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host(1)                                                   host(1)


       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 pro-
           vide it.

       No nameservers for zone found
           It was not possible to retrieve the name of any name-
           server 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.





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host(1)                                                   host(1)


       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 hap-
           pen 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



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host(1)                                                   host(1)


           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 defini-
           tion of glue records or other information in the par-
           ent zone, which is not kept in sync with the defini-
           tion 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
           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



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host(1)                                                   host(1)


           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 suppos-
           edly authoritative nameservers, the SOA information
           turns out to be not authoritative.  This could be
           determined by making a query without nameserver recur-
           sion turned on.

       zone SOA primary server is not advertised via NS
           The primary nameserver is not among the list of name-
           servers 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 deci-
           mal notation in the zone file. This may lead to syn-
           chronization 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 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.




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host(1)                                                   host(1)


       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. Nev-
           ertheless 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 sta-
       tus.

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 con-
       tains an abbreviation, white space, and then the fully
       qualified host name. The name of this file must be speci-
       fied in the environment variable HOSTALIASES.





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host(1)                                                   host(1)


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 cur-
       rently 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
       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>



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host(1)                                                   host(1)


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























































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