1HOST(1) BIND 9 HOST(1)
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6 host - DNS lookup utility
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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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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.
17 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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26 -4 This option specifies that only IPv4 should be used for query
27 transport. See also the -6 option.
28 -6 This option specifies that only IPv6 should be used for query
30 transport. See also the -4 option.
31 -a The -a ("all") option is normally equivalent to -v -t ANY. It
33 also affects the behavior of the -l list zone option.
34 -A The -A ("almost all") option is equivalent to -a, except that
36 RRSIG, NSEC, and NSEC3 records are omitted from the output.
37 -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).
42 -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.
48 -d This option prints debugging traces, and is equivalent to the -v
50 verbose option.
51 -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 Together, the -l -a options print all records in the zone.
57 -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 -p port
67 This option specifies the port to query on the server. The de‐
68 fault is 53.
69 -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.
77 -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 -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 -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 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.
98 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 -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 -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 -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.
118 -V This option prints the version number and exits.
120 -w This option sets "wait forever": the query timeout is set to the
122 maximum possible. See also the -W option.
123 -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.
128 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 See also the -w option.
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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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144 /etc/resolv.conf
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147 dig(1), named(8).
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150 Internet Systems Consortium
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153 2021, Internet Systems Consortium
1549.16.16-RH HOST(1)