1.\" $OpenBSD: host.1,v 1.4 2022/03/31 17:27:24 naddy Exp $ 2.\" 3.\" Copyright (C) 2000-2002, 2004, 2005, 2007-2009, 2014-2018 Internet Systems Consortium, Inc. ("ISC") 4.\" 5.\" Permission to use, copy, modify, and/or distribute this software for any 6.\" purpose with or without fee is hereby granted, provided that the above 7.\" copyright notice and this permission notice appear in all copies. 8.\" 9.\" THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH 10.\" REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY 11.\" AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, 12.\" INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM 13.\" LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE 14.\" OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR 15.\" PERFORMANCE OF THIS SOFTWARE. 16.\" 17.Dd $Mdocdate: March 31 2022 $ 18.Dt HOST 1 19.Os 20.Sh NAME 21.Nm host 22.Nd DNS lookup utility 23.Sh SYNOPSIS 24.Nm 25.Op Fl 46aCdilrsTVvw 26.Op Fl c Ar class 27.Op Fl m Ar flag 28.Op Fl N Ar ndots 29.Op Fl R Ar number 30.Op Fl t Ar type 31.Op Fl W Ar wait 32.Ar name 33.Op Ar server 34.Sh DESCRIPTION 35The 36.Nm 37command is a simple utility for performing DNS lookups. 38It is normally used to convert names to IP addresses and vice versa. 39.Pp 40.Ar name 41is the domain name that is to be looked up. 42It can also be a dotted-decimal IPv4 address or a colon-delimited IPv6 43address, in which case 44.Nm 45will by default perform a reverse lookup for that address. 46.Ar server 47is an optional argument which is either the name or IP address of the name 48server that 49.Nm 50should query instead of the server or servers listed in 51.Pa /etc/resolv.conf . 52.Pp 53The options are as follows: 54.Bl -tag -width Ds 55.It Fl 4 56Use IPv4 only for query transport. 57.It Fl 6 58Use IPv6 only for query transport. 59.It Fl a 60"All". 61The 62.Fl a 63option is normally equivalent to 64.Fl v 65.Fl t Cm ANY . 66It also affects the behaviour of the 67.Fl l 68list zone option. 69.It Fl C 70Check consistency: 71.Nm 72will query the SOA records for zone 73.Ar name 74from all the listed authoritative name servers for that zone. 75The list of name servers is defined by the NS records that are found for the 76zone. 77.It Fl c Ar class 78Query class: This can be used to lookup 79.Cm HS 80(Hesiod) 81or 82.Cm CH 83(Chaosnet) class resource records. 84The default class is 85.Cm IN 86(Internet). 87.It Fl d 88Print debugging traces. 89Equivalent to the 90.Fl v 91verbose option. 92.It Fl i 93Obsolete. 94Use the IP6.INT domain for reverse lookups of IPv6 addresses as defined in 95RFC 1886 and deprecated in RFC 4159. 96The default is to use IP6.ARPA as specified in RFC 3596. 97.It Fl l 98List zone: 99The 100.Nm 101command performs a zone transfer of 102zone 103.Ar name 104and prints out the NS, PTR and address records (A/AAAA). 105.Pp 106Together, the 107.Fl l 108.Fl a 109options print all records in the zone. 110.It Fl m Ar flag 111Memory usage debugging: the flag can be 112.Cm record , 113.Cm usage , 114or 115.Cm trace . 116You can specify the 117.Fl m 118option more than once to set multiple flags. 119.It Fl N Ar ndots 120The number of dots that have to be in 121.Ar name 122for it to be considered absolute. 123The default value is that defined using the ndots statement in 124.Pa /etc/resolv.conf , 125or 1 if no ndots statement is present. 126Names with fewer dots are interpreted as relative names and will be searched for 127in the domains listed in the 128.Vt search 129or 130.Vt domain 131directive in 132.Pa /etc/resolv.conf . 133.It Fl R Ar number 134Number of retries for UDP queries: 135If 136.Ar number 137is negative or zero, the number of retries will default to 1. 138The default value is 1. 139.It Fl r 140Non-recursive query: 141Setting this option clears the RD (recursion desired) bit in the query. 142This should mean that the name server receiving the query will not attempt to 143resolve 144.Ar name . 145The 146.Fl r 147option enables 148.Nm 149to mimic the behavior of a name server by making non-recursive queries and 150expecting to receive answers to those queries that can be referrals to other 151name servers. 152.It Fl s 153Do 154.Em not 155send the query to the next name server if any server responds with a SERVFAIL 156response, which is the reverse of normal stub resolver behavior. 157.It Fl T 158TCP: 159By default, 160.Nm 161uses UDP when making queries. 162The 163.Fl T 164option makes it use a TCP connection when querying the name server. 165TCP will be automatically selected for queries that require it, such as zone 166transfer (AXFR) requests. 167.It Fl t Ar type 168Query type: 169The 170.Ar type 171argument can be any recognized query type: 172.Cm CNAME , 173.Cm NS , 174.Cm SOA , 175.Cm TXT , 176.Cm DNSKEY , 177.Cm AXFR , 178etc. 179.Pp 180When no query type is specified, 181.Nm 182automatically selects an appropriate query type. 183By default, it looks for A, AAAA, and MX records. 184If the 185.Fl C 186option is given, queries will be made for SOA records. 187If 188.Ar name 189is a dotted-decimal IPv4 address or colon-delimited IPv6 address, 190.Nm 191will query for PTR records. 192.Pp 193If a query type of 194.Cm IXFR 195is chosen, the starting serial number can be specified by appending an equal 196followed by the starting serial number (like 197.Fl t Cm IXFR= Ns Ar 12345678 ) . 198.It Fl V 199Print the version number and exit. 200.It Fl v 201Verbose output. 202Equivalent to the 203.Fl d 204debug option. 205.It Fl W Ar wait 206Timeout: Wait for up to 207.Ar wait 208seconds for a reply. 209If 210.Ar wait 211is less than one, the wait interval is set to one second. 212.Pp 213By default, 214.Nm 215will wait for 5 seconds for UDP responses and 10 seconds for TCP connections. 216.It Fl w 217Wait forever: The query timeout is set to the maximum possible. 218.El 219.Sh FILES 220.Pa /etc/resolv.conf 221.Sh SEE ALSO 222.Xr dig 1 223.Sh AUTHORS 224.An -nosplit 225.An Internet Systems Consortium, Inc . 226