NAME

       host - DNS lookup utility

SYNOPSIS

       host  [-aACdlnrsTUwv]  [-c class] [-N ndots] [-p port] [-R number] [-t type] [-W wait] [-m
       flag] [ [-4] | [-6] ] [-v] [-V] {name} [server]

DESCRIPTION

       host is a simple utility for performing DNS lookups. It is normally used to convert  names
       to  IP  addresses  and  vice  versa. When no arguments or options are given, host prints a
       short summary of its command-line arguments and options.

       name is the domain name that is to be looked up. It can  also  be  a  dotted-decimal  IPv4
       address  or  a  colon-delimited  IPv6  address,  in  which case host by default performs a
       reverse lookup for that address.  server is an optional argument which is either the  name
       or  IP  address of the name server that host should query instead of the server or servers
       listed in /etc/resolv.conf.

OPTIONS

       -4     This option specifies that only IPv4 should be used for query transport.  See  also
              the -6 option.

       -6     This  option  specifies that only IPv6 should be used for query transport. See also
              the -4 option.

       -a     The -a ("all") option is normally equivalent to -v -t  ANY.  It  also  affects  the
              behavior of the -l list zone option.

       -A     The  -A  ("almost  all")  option  is equivalent to -a, except that RRSIG, NSEC, and
              NSEC3 records are omitted from the output.

       -c class
              This option specifies the query class, which can be used to lookup HS  (Hesiod)  or
              CH (Chaosnet) class resource records. The default class is IN (Internet).

       -C     This  option  indicates  that  named  should  check  consistency, meaning that host
              queries the SOA records for zone  name  from  all  the  listed  authoritative  name
              servers  for  that zone. The list of name servers is defined by the NS records that
              are found for the zone.

       -d     This option prints debugging traces, and is equivalent to the -v verbose option.

       -l     This option tells named to list the zone, meaning the host command performs a  zone
              transfer of zone name and prints out the NS, PTR, and address records (A/AAAA).

              Together, the -l -a options print all records in the zone.

       -N ndots
              This  option specifies the number of dots (ndots) that have to be in name for it to
              be considered absolute. The default value is that defined using the ndots statement
              in  /etc/resolv.conf,  or 1 if no ndots statement is present. Names with fewer dots
              are interpreted as relative names, and are searched for in the  domains  listed  in
              the search or domain directive in /etc/resolv.conf.

       -p port
              This option specifies the port to query on the server. The default is 53.

       -r     This  option  specifies  a  non-recursive  query; setting this option clears the RD
              (recursion desired) bit in the query. This means that the name server receiving the
              query  does  not  attempt  to resolve name. The -r option enables host to mimic the
              behavior of a name server by making non-recursive queries, and expecting to receive
              answers to those queries that can be referrals to other name servers.

       -R number
              This  option specifies the number of retries for UDP queries. If number is negative
              or zero, the number of retries is silently set to 1. The default value is 1, or the
              value of the attempts option in /etc/resolv.conf, if set.

       -s     This  option tells named not to send the query to the next nameserver if any server
              responds with a SERVFAIL response, which is the reverse  of  normal  stub  resolver
              behavior.

       -t type
              This option specifies the query type. The type argument can be any recognized query
              type: CNAME, NS, SOA, TXT, DNSKEY, AXFR, etc.

              When no query type is specified, host automatically selects  an  appropriate  query
              type.  By default, it looks for A, AAAA, and MX records. If the -C option is given,
              queries are made for SOA records. If name  is  a  dotted-decimal  IPv4  address  or
              colon-delimited IPv6 address, host queries for PTR records.

              If  a  query type of IXFR is chosen, the starting serial number can be specified by
              appending an equals sign (=), followed by the  starting  serial  number,  e.g.,  -t
              IXFR=12345678.

       -T, -U This  option  specifies  TCP or UDP. By default, host uses UDP when making queries;
              the -T option makes it use a TCP connection when querying the name server.  TCP  is
              automatically  selected  for  queries that require it, such as zone transfer (AXFR)
              requests. Type ANY queries default to TCP, but can be forced to use  UDP  initially
              via -U.

       -m flag
              This  option  sets memory usage debugging: the flag can be record, usage, or trace.
              The -m option can be specified more than once to set multiple flags.

       -v     This option sets verbose output, and is equivalent to the -d debug option.  Verbose
              output can also be enabled by setting the debug option in /etc/resolv.conf.

       -V     This option prints the version number and exits.

       -w     This  option sets "wait forever": the query timeout is set to the maximum possible.
              See also the -W option.

       -W wait
              This options sets the length of the wait timeout, indicating that named should wait
              for  up  to  wait seconds for a reply. If wait is less than 1, the wait interval is
              set to 1 second.

              By default, host waits for 5 seconds for UDP  responses  and  10  seconds  for  TCP
              connections.   These   defaults   can  be  overridden  by  the  timeout  option  in
              /etc/resolv.conf.

              See also the -w option.

IDN SUPPORT

       If host has been built with IDN (internationalized domain name) support, it can accept and
       display non-ASCII domain names. host appropriately converts character encoding of a domain
       name before sending a request to a DNS server or displaying a reply from the  server.   To
       turn off IDN support, define the IDN_DISABLE environment variable. IDN support is disabled
       if the variable is set when host runs.

FILES

       /etc/resolv.conf

SEE ALSO

       dig(1), named(8).

AUTHOR

       Internet Systems Consortium

COPYRIGHT

       2024, Internet Systems Consortium