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

       2025, Internet Systems Consortium