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 .. iscman:: host 15 .. program:: host 16 .. _man_host: 17 18 host - DNS lookup utility 19 ------------------------- 20 21 Synopsis 22 ~~~~~~~~ 23 24 :program:`host` [**-aACdlnrsTUwv**] [**-c** class] [**-N** ndots] [**-p** port] [**-R** number] [**-t** type] [**-W** wait] [**-m** flag] [ [**-4**] | [**-6**] ] [**-v**] [**-V**] {name} [server] 25 26 Description 27 ~~~~~~~~~~~ 28 29 :program:`host` is a simple utility for performing DNS lookups. It is normally 30 used to convert names to IP addresses and vice versa. When no arguments 31 or options are given, :program:`host` prints a short summary of its 32 command-line arguments and options. 33 34 ``name`` is the domain name that is to be looked up. It can also be a 35 dotted-decimal IPv4 address or a colon-delimited IPv6 address, in which 36 case :program:`host` by default performs a reverse lookup for that address. 37 ``server`` is an optional argument which is either the name or IP 38 address of the name server that :program:`host` should query instead of the 39 server or servers listed in ``/etc/resolv.conf``. 40 41 Options 42 ~~~~~~~ 43 44 .. option:: -4 45 46 This option specifies that only IPv4 should be used for query transport. See also the :option:`-6` option. 47 48 .. option:: -6 49 50 This option specifies that only IPv6 should be used for query transport. See also the :option:`-4` option. 51 52 .. option:: -a 53 54 The :option:`-a` ("all") option is normally equivalent to :option:`-v` :option:`-t ANY <-t>`. It 55 also affects the behavior of the :option:`-l` list zone option. 56 57 .. option:: -A 58 59 The :option:`-A` ("almost all") option is equivalent to :option:`-a`, except that RRSIG, 60 NSEC, and NSEC3 records are omitted from the output. 61 62 .. option:: -c class 63 64 This option specifies the query class, which can be used to lookup HS (Hesiod) or CH (Chaosnet) 65 class resource records. The default class is IN (Internet). 66 67 .. option:: -C 68 69 This option indicates that :iscman:`named` should check consistency, meaning that :program:`host` queries the SOA records for zone 70 ``name`` from all the listed authoritative name servers for that 71 zone. The list of name servers is defined by the NS records that are 72 found for the zone. 73 74 .. option:: -d 75 76 This option prints debugging traces, and is equivalent to the :option:`-v` verbose option. 77 78 .. option:: -l 79 80 This option tells :iscman:`named` to list the zone, meaning the :program:`host` command performs a zone transfer of zone 81 ``name`` and prints out the NS, PTR, and address records (A/AAAA). 82 83 Together, the :option:`-l` :option:`-a` options print all records in the zone. 84 85 .. option:: -N ndots 86 87 This option specifies the number of dots (``ndots``) that have to be in ``name`` for it to be 88 considered absolute. The default value is that defined using the 89 ``ndots`` statement in ``/etc/resolv.conf``, or 1 if no ``ndots`` statement 90 is present. Names with fewer dots are interpreted as relative names, 91 and are searched for in the domains listed in the ``search`` or 92 ``domain`` directive in ``/etc/resolv.conf``. 93 94 .. option:: -p port 95 96 This option specifies the port to query on the server. The default is 53. 97 98 .. option:: -r 99 100 This option specifies a non-recursive query; setting this option clears the RD (recursion 101 desired) bit in the query. This means that the name server 102 receiving the query does not attempt to resolve ``name``. The :option:`-r` 103 option enables :program:`host` to mimic the behavior of a name server by 104 making non-recursive queries, and expecting to receive answers to 105 those queries that can be referrals to other name servers. 106 107 .. option:: -R number 108 109 This option specifies the number of retries for UDP queries. If ``number`` is negative or zero, 110 the number of retries is silently set to 1. The default value is 1, or 111 the value of the ``attempts`` option in ``/etc/resolv.conf``, if set. 112 113 .. option:: -s 114 115 This option tells :iscman:`named` *not* to send the query to the next nameserver if any server responds 116 with a SERVFAIL response, which is the reverse of normal stub 117 resolver behavior. 118 119 .. option:: -t type 120 121 This option specifies the query type. The ``type`` argument can be any recognized query type: 122 CNAME, NS, SOA, TXT, DNSKEY, AXFR, etc. 123 124 When no query type is specified, :program:`host` automatically selects an 125 appropriate query type. By default, it looks for A, AAAA, MX, and HTTPS 126 records. If the :option:`-C` option is given, queries are made for SOA 127 records. If ``name`` is a dotted-decimal IPv4 address or 128 colon-delimited IPv6 address, :program:`host` queries for PTR records. 129 130 If a query type of IXFR is chosen, the starting serial number can be 131 specified by appending an equals sign (=), followed by the starting serial 132 number, e.g., :option:`-t IXFR=12345678 <-t>`. 133 134 .. option:: -T, -U 135 136 This option specifies TCP or UDP. By default, :program:`host` uses UDP when making queries; the 137 :option:`-T` option makes it use a TCP connection when querying the name 138 server. TCP is automatically selected for queries that require 139 it, such as zone transfer (AXFR) requests. Type ``ANY`` queries default 140 to TCP, but can be forced to use UDP initially via :option:`-U`. 141 142 .. option:: -m flag 143 144 This option sets memory usage debugging: the flag can be ``record``, ``usage``, or 145 ``trace``. The :option:`-m` option can be specified more than once to set 146 multiple flags. 147 148 .. option:: -v 149 150 This option sets verbose output, and is equivalent to the :option:`-d` debug option. Verbose output 151 can also be enabled by setting the ``debug`` option in 152 ``/etc/resolv.conf``. 153 154 .. option:: -V 155 156 This option prints the version number and exits. 157 158 .. option:: -w 159 160 This option sets "wait forever": the query timeout is set to the maximum possible. See 161 also the :option:`-W` option. 162 163 .. option:: -W wait 164 165 This options sets the length of the wait timeout, indicating that :iscman:`named` should wait for up to ``wait`` seconds for a reply. If ``wait`` is 166 less than 1, the wait interval is set to 1 second. 167 168 By default, :program:`host` waits for 5 seconds for UDP responses and 10 169 seconds for TCP connections. These defaults can be overridden by the 170 ``timeout`` option in ``/etc/resolv.conf``. 171 172 See also the :option:`-w` option. 173 174 IDN Support 175 ~~~~~~~~~~~ 176 177 If :program:`host` has been built with IDN (internationalized domain name) 178 support, it can accept and display non-ASCII domain names. :program:`host` 179 appropriately converts character encoding of a domain name before sending 180 a request to a DNS server or displaying a reply from the server. 181 To turn off IDN support, define the ``IDN_DISABLE`` 182 environment variable. IDN support is disabled if the variable is set 183 when :program:`host` runs. 184 185 Files 186 ~~~~~ 187 188 ``/etc/resolv.conf`` 189 190 See Also 191 ~~~~~~~~ 192 193 :iscman:`dig(1) <dig>`, :iscman:`named(8) <named>`. 194
Indexes created Tue Mar 03 05:31:39 UTC 2026