1.\" $OpenBSD: host.1,v 1.2 2021/06/12 06:39:17 jmc 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: June 12 2021 $ 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". The 61.Fl a 62option is normally equivalent to 63.Fl v 64.Fl t Cm ANY . 65It also affects the behaviour of the 66.Fl l 67list zone option. 68.It Fl C 69Check consistency: 70.Nm 71will query the SOA records for zone 72.Ar name 73from all the listed authoritative name servers for that zone. 74The list of name servers is defined by the NS records that are found for the 75zone. 76.It Fl c Ar class 77Query class: This can be used to lookup 78.Cm HS 79(Hesiod) 80or 81.Cm CH 82(Chaosnet) class resource records. 83The default class is 84.Cm IN 85(Internet). 86.It Fl d 87Print debugging traces. 88Equivalent to the 89.Fl v 90verbose option. 91.It Fl i 92Obsolete. 93Use the IP6.INT domain for reverse lookups of IPv6 addresses as defined in 94RFC 1886 and deprecated in RFC 4159. 95The default is to use IP6.ARPA as specified in RFC 3596. 96.It Fl l 97List zone: 98The 99.Nm 100command performs a zone transfer of 101zone 102.Ar name 103and prints out the NS, PTR and address records (A/AAAA). 104.Pp 105Together, the 106.Fl l 107.Fl a 108options print all records in the zone. 109.It Fl m Ar flag 110Memory usage debugging: the flag can be 111.Cm record , 112.Cm usage , 113or 114.Cm trace . 115You can specify the 116.Fl m 117option more than once to set multiple flags. 118.It Fl N Ar ndots 119The number of dots that have to be in 120.Ar name 121for it to be considered absolute. 122The default value is that defined using the ndots statement in 123.Pa /etc/resolv.conf , 124or 1 if no ndots statement is present. 125Names with fewer dots are interpreted as relative names and will be searched for 126in the domains listed in the 127.Vt search 128or 129.Vt domain 130directive in 131.Pa /etc/resolv.conf . 132.It Fl R Ar number 133Number of retries for UDP queries: 134If 135.Ar number 136is negative or zero, the number of retries will default to 1. The default value 137is 1. 138.It Fl r 139Non-recursive query: 140Setting this option clears the RD (recursion desired) bit in the query. 141This should mean that the name server receiving the query will not attempt to 142resolve 143.Ar name . 144The 145.Fl r 146option enables 147.Nm 148to mimic the behavior of a name server by making non-recursive queries and 149expecting to receive answers to those queries that can be referrals to other 150name servers. 151.It Fl s 152Do 153.Em not 154send the query to the next name server if any server responds with a SERVFAIL 155response, which is the reverse of normal stub resolver behavior. 156.It Fl T 157TCP: 158By default, 159.Nm 160uses UDP when making queries. 161The 162.Fl T 163option makes it use a TCP connection when querying the name server. 164TCP will be automatically selected for queries that require it, such as zone 165transfer (AXFR) requests. 166.It Fl t Ar type 167Query type: 168The 169.Ar type 170argument can be any recognized query type: 171.Cm CNAME , 172.Cm NS , 173.Cm SOA , 174.Cm TXT , 175.Cm DNSKEY , 176.Cm AXFR , 177etc. 178.Pp 179When no query type is specified, 180.Nm 181automatically selects an appropriate query type. 182By default, it looks for A, AAAA, and MX records. 183If the 184.Fl C 185option is given, queries will be made for SOA records. 186If 187.Ar name 188is a dotted-decimal IPv4 address or colon-delimited IPv6 address, 189.Nm 190will query for PTR records. 191.Pp 192If a query type of 193.Cm IXFR 194is chosen the starting serial number can be specified by appending an equal 195followed by the starting serial number (like 196.Fl t Cm IXFR= Ns Ar 12345678 ) . 197.It Fl V 198Print the version number and exit. 199.It Fl v 200Verbose output. 201Equivalent to the 202.Fl d 203debug option. 204.It Fl W Ar wait 205Timeout: Wait for up to 206.Ar wait 207seconds for a reply. 208If 209.Ar wait 210is less than one, the wait interval is set to one second. 211.Pp 212By default, 213.Nm 214will wait for 5 seconds for UDP responses and 10 seconds for TCP connections. 215.It Fl w 216Wait forever: The query timeout is set to the maximum possible. 217.El 218.Sh FILES 219.Pa /etc/resolv.conf 220.Sh SEE ALSO 221.Xr dig 1 222.Sh AUTHORS 223.An -nosplit 224.An Internet Systems Consortium, Inc . 225