1.. Copyright (C) Internet Systems Consortium, Inc. ("ISC") 2.. 3.. SPDX-License-Identifier: MPL-2.0 4.. 5.. This Source Code Form is subject to the terms of the Mozilla Public 6.. License, v. 2.0. If a copy of the MPL was not distributed with this 7.. file, you can obtain one at https://mozilla.org/MPL/2.0/. 8.. 9.. See the COPYRIGHT file distributed with this work for additional 10.. information regarding copyright ownership. 11 12.. highlight: console 13 14.. _man_host: 15 16host - DNS lookup utility 17------------------------- 18 19Synopsis 20~~~~~~~~ 21 22:program:`host` [**-aACdlnrsTUwv**] [**-c** class] [**-N** ndots] [**-p** port] [**-R** number] [**-t** type] [**-W** wait] [**-m** flag] [ [**-4**] | [**-6**] ] [**-v**] [**-V**] {name} [server] 23 24Description 25~~~~~~~~~~~ 26 27``host`` is a simple utility for performing DNS lookups. It is normally 28used to convert names to IP addresses and vice versa. When no arguments 29or options are given, ``host`` prints a short summary of its 30command-line arguments and options. 31 32``name`` is the domain name that is to be looked up. It can also be a 33dotted-decimal IPv4 address or a colon-delimited IPv6 address, in which 34case ``host`` by default performs a reverse lookup for that address. 35``server`` is an optional argument which is either the name or IP 36address of the name server that ``host`` should query instead of the 37server or servers listed in ``/etc/resolv.conf``. 38 39Options 40~~~~~~~ 41 42``-4`` 43 This option specifies that only IPv4 should be used for query transport. See also the ``-6`` option. 44 45``-6`` 46 This option specifies that only IPv6 should be used for query transport. See also the ``-4`` option. 47 48``-a`` 49 The ``-a`` ("all") option is normally equivalent to ``-v -t ANY``. It 50 also affects the behavior of the ``-l`` list zone option. 51 52``-A`` 53 The ``-A`` ("almost all") option is equivalent to ``-a``, except that RRSIG, 54 NSEC, and NSEC3 records are omitted from the output. 55 56``-c class`` 57 This option specifies the query class, which can be used to lookup HS (Hesiod) or CH (Chaosnet) 58 class resource records. The default class is IN (Internet). 59 60``-C`` 61 This option indicates that ``named`` should check consistency, meaning that ``host`` queries the SOA records for zone 62 ``name`` from all the listed authoritative name servers for that 63 zone. The list of name servers is defined by the NS records that are 64 found for the zone. 65 66``-d`` 67 This option prints debugging traces, and is equivalent to the ``-v`` verbose option. 68 69``-l`` 70 This option tells ``named`` to list the zone, meaning the ``host`` command performs a zone transfer of zone 71 ``name`` and prints out the NS, PTR, and address records (A/AAAA). 72 73 Together, the ``-l -a`` options print all records in the zone. 74 75``-N ndots`` 76 This option specifies the number of dots (``ndots``) that have to be in ``name`` for it to be 77 considered absolute. The default value is that defined using the 78 ``ndots`` statement in ``/etc/resolv.conf``, or 1 if no ``ndots`` statement 79 is present. Names with fewer dots are interpreted as relative names, 80 and are searched for in the domains listed in the ``search`` or 81 ``domain`` directive in ``/etc/resolv.conf``. 82 83``-p port`` 84 This option specifies the port to query on the server. The default is 53. 85 86``-r`` 87 This option specifies a non-recursive query; setting this option clears the RD (recursion 88 desired) bit in the query. This means that the name server 89 receiving the query does not attempt to resolve ``name``. The ``-r`` 90 option enables ``host`` to mimic the behavior of a name server by 91 making non-recursive queries, and expecting to receive answers to 92 those queries that can be referrals to other name servers. 93 94``-R number`` 95 This option specifies the number of retries for UDP queries. If ``number`` is negative or zero, 96 the number of retries is silently set to 1. The default value is 1, or 97 the value of the ``attempts`` option in ``/etc/resolv.conf``, if set. 98 99``-s`` 100 This option tells ``named`` *not* to send the query to the next nameserver if any server responds 101 with a SERVFAIL response, which is the reverse of normal stub 102 resolver behavior. 103 104``-t type`` 105 This option specifies the query type. The ``type`` argument can be any recognized query type: 106 CNAME, NS, SOA, TXT, DNSKEY, AXFR, etc. 107 108 When no query type is specified, ``host`` automatically selects an 109 appropriate query type. By default, it looks for A, AAAA, and MX 110 records. If the ``-C`` option is given, queries are made for SOA 111 records. If ``name`` is a dotted-decimal IPv4 address or 112 colon-delimited IPv6 address, ``host`` queries for PTR records. 113 114 If a query type of IXFR is chosen, the starting serial number can be 115 specified by appending an equals sign (=), followed by the starting serial 116 number, e.g., ``-t IXFR=12345678``. 117 118``-T``; ``-U`` 119 This option specifies TCP or UDP. By default, ``host`` uses UDP when making queries; the 120 ``-T`` option makes it use a TCP connection when querying the name 121 server. TCP is automatically selected for queries that require 122 it, such as zone transfer (AXFR) requests. Type ``ANY`` queries default 123 to TCP, but can be forced to use UDP initially via ``-U``. 124 125``-m flag`` 126 This option sets memory usage debugging: the flag can be ``record``, ``usage``, or 127 ``trace``. The ``-m`` option can be specified more than once to set 128 multiple flags. 129 130``-v`` 131 This option sets verbose output, and is equivalent to the ``-d`` debug option. Verbose output 132 can also be enabled by setting the ``debug`` option in 133 ``/etc/resolv.conf``. 134 135``-V`` 136 This option prints the version number and exits. 137 138``-w`` 139 This option sets "wait forever": the query timeout is set to the maximum possible. See 140 also the ``-W`` option. 141 142``-W wait`` 143 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 144 less than 1, the wait interval is set to 1 second. 145 146 By default, ``host`` waits for 5 seconds for UDP responses and 10 147 seconds for TCP connections. These defaults can be overridden by the 148 ``timeout`` option in ``/etc/resolv.conf``. 149 150 See also the ``-w`` option. 151 152IDN Support 153~~~~~~~~~~~ 154 155If ``host`` has been built with IDN (internationalized domain name) 156support, it can accept and display non-ASCII domain names. ``host`` 157appropriately converts character encoding of a domain name before sending 158a request to a DNS server or displaying a reply from the server. 159To turn off IDN support, define the ``IDN_DISABLE`` 160environment variable. IDN support is disabled if the variable is set 161when ``host`` runs. 162 163Files 164~~~~~ 165 166``/etc/resolv.conf`` 167 168See Also 169~~~~~~~~ 170 171:manpage:`dig(1)`, :manpage:`named(8)`. 172