Updated: 2021/Apr/14


HOST(1)                             BIND 9                             HOST(1)



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
       2021, Internet Systems Consortium



9.16.12                                                                HOST(1)