1HOST(1)                             BIND 9                             HOST(1)
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NAME

6       host - DNS lookup utility
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SYNOPSIS

9       host  [-aACdlnrsTUwv]  [-c  class] [-N ndots] [-p port] [-R number] [-t
10       type] [-W wait] [-m flag] [ [-4] | [-6] ] [-v] [-V] {name} [server]
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DESCRIPTION

13       host is a simple utility for performing DNS  lookups.  It  is  normally
14       used to convert names to IP addresses and vice versa. When no arguments
15       or options are given, host prints a short summary of  its  command-line
16       arguments and options.
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18       name  is the domain name that is to be looked up. It can also be a dot‐
19       ted-decimal IPv4 address or a colon-delimited IPv6  address,  in  which
20       case  host  by  default  performs  a  reverse  lookup for that address.
21       server is an optional argument which is either the name or  IP  address
22       of  the  name  server  that  host should query instead of the server or
23       servers listed in /etc/resolv.conf.
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OPTIONS

26       -4     This option specifies that only IPv4 should be  used  for  query
27              transport. See also the -6 option.
28
29       -6     This  option  specifies  that only IPv6 should be used for query
30              transport. See also the -4 option.
31
32       -a     The -a ("all") option is normally equivalent to -v  -t  ANY.  It
33              also affects the behavior of the -l list zone option.
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35       -A     The  -A  ("almost  all") option is equivalent to -a, except that
36              RRSIG, NSEC, and NSEC3 records are omitted from the output.
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38       -c class
39              This option specifies the query class,  which  can  be  used  to
40              lookup  HS (Hesiod) or CH (Chaosnet) class resource records. The
41              default class is IN (Internet).
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43       -C     This option indicates that named should check consistency, mean‐
44              ing that host queries the SOA records for zone name from all the
45              listed authoritative name servers for that  zone.  The  list  of
46              name servers is defined by the NS records that are found for the
47              zone.
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49       -d     This option prints debugging traces, and is equivalent to the -v
50              verbose option.
51
52       -l     This  option  tells  named` to list the zone, meaning the ``host
53              command performs a zone transfer of zone name and prints out the
54              NS, PTR, and address records (A/AAAA).
55
56              Together, the -l -a options print all records in the zone.
57
58       -N ndots
59              This option specifies the number of dots (ndots) that have to be
60              in name for it to be considered absolute. The default  value  is
61              that defined using the ndots statement in /etc/resolv.conf, or 1
62              if no ndots statement is present. Names with fewer dots are  in‐
63              terpreted as relative names, and are searched for in the domains
64              listed in the search or domain directive in /etc/resolv.conf.
65
66       -p port
67              This option specifies the port to query on the server.  The  de‐
68              fault is 53.
69
70       -r     This option specifies a non-recursive query; setting this option
71              clears the RD (recursion desired) bit in the query.  This  means
72              that the name server receiving the query does not attempt to re‐
73              solve name. The -r option enables host to mimic the behavior  of
74              a  name server by making non-recursive queries, and expecting to
75              receive answers to those queries that can be referrals to  other
76              name servers.
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78       -R number
79              This  option specifies the number of retries for UDP queries. If
80              number is negative or zero, the number of  retries  is  silently
81              set  to  1. The default value is 1, or the value of the attempts
82              option in /etc/resolv.conf, if set.
83
84       -s     This option tells named not to send the query to the next  name‐
85              server if any server responds with a SERVFAIL response, which is
86              the reverse of normal stub resolver behavior.
87
88       -t type
89              This option specifies the query type. The type argument  can  be
90              any  recognized  query  type: CNAME, NS, SOA, TXT, DNSKEY, AXFR,
91              etc.
92
93              When no query type is specified, host automatically  selects  an
94              appropriate query type. By default, it looks for A, AAAA, and MX
95              records. If the -C option is given, queries  are  made  for  SOA
96              records.  If  name is a dotted-decimal IPv4 address or colon-de‐
97              limited IPv6 address, host queries for PTR records.
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99              If a query type of IXFR is chosen, the  starting  serial  number
100              can  be  specified  by appending an equals sign (=), followed by
101              the starting serial number, e.g., -t IXFR=12345678.
102
103       -T; -U This option specifies TCP or UDP. By default, host uses UDP when
104              making queries; the -T option makes it use a TCP connection when
105              querying the name server.  TCP  is  automatically  selected  for
106              queries  that require it, such as zone transfer (AXFR) requests.
107              Type ANY queries default to TCP, but can be forced  to  use  UDP
108              initially via -U.
109
110       -m flag
111              This option sets memory usage debugging: the flag can be record,
112              usage, or trace. The -m option can be specified more  than  once
113              to set multiple flags.
114
115       -v     This option sets verbose output, and is equivalent to the -d de‐
116              bug option. Verbose output can also be enabled  by  setting  the
117              debug option in /etc/resolv.conf.
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119       -V     This option prints the version number and exits.
120
121       -w     This option sets "wait forever": the query timeout is set to the
122              maximum possible. See also the -W option.
123
124       -W wait
125              This options sets the length of  the  wait  timeout,  indicating
126              that  named  should  wait for up to wait seconds for a reply. If
127              wait is less than 1, the wait interval is set to 1 second.
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129              By default, host waits for 5 seconds for UDP  responses  and  10
130              seconds for TCP connections. These defaults can be overridden by
131              the timeout option in /etc/resolv.conf.
132
133              See also the -w option.
134

IDN SUPPORT

136       If host has been built with IDN (internationalized  domain  name)  sup‐
137       port,  it can accept and display non-ASCII domain names. host appropri‐
138       ately converts character encoding of a domain name before sending a re‐
139       quest  to  a DNS server or displaying a reply from the server.  To turn
140       off IDN support, define the IDN_DISABLE environment variable. IDN  sup‐
141       port is disabled if the variable is set when host runs.
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FILES

144       /etc/resolv.conf
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SEE ALSO

147       dig(1), named(8).
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AUTHOR

150       Internet Systems Consortium
151
153       2021, Internet Systems Consortium
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1589.16.16-RH                                                             HOST(1)
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