HOST(1) BIND9 HOST(1)
NAME
host - DNS lookup utility
SYNOPSIS
host [-aCdlnrsTwv] [-c class] [-N ndots] [-R number] [-t type] [-W wait] [-m flag] [-4] [-6] {name}
[server]
DESCRIPTION
host is a simple utility for performing DNS lookups. It is normally used to convert names to IP
addresses and vice versa. When no arguments or options are given, host prints a short summary of its
command line arguments and options.
name is the domain name that is to be looked up. It can also be a dotted-decimal IPv4 address or a
colon-delimited IPv6 address, in which case host will by default perform a reverse lookup for that
address. server is an optional argument which is either the name or IP address of the name server
that host should query instead of the server or servers listed in /etc/resolv.conf.
The -a (all) option is equivalent to setting the -v option and asking host to make a query of type
ANY.
When the -C option is used, host will attempt to display the SOA records for zone name from all the
listed authoritative name servers for that zone. The list of name servers is defined by the NS
records that are found for the zone.
The -c option instructs to make a DNS query of class class. This can be used to lookup Hesiod or
Chaosnet class resource records. The default class is IN (Internet).
Verbose output is generated by host when the -d or -v option is used. The two options are equivalent.
They have been provided for backwards compatibility. In previous versions, the -d option switched on
debugging traces and -v enabled verbose output.
List mode is selected by the -l option. This makes host perform a zone transfer for zone name.
Transfer the zone printing out the NS, PTR and address records (A/AAAA). If combined with -a all
records will be printed.
The -i option specifies that reverse lookups of IPv6 addresses should use the IP6.INT domain as
defined in RFC1886. The default is to use IP6.ARPA.
The -N option sets the number of dots that have to be in name for it to be considered absolute. The
default value is that defined using the ndots statement in /etc/resolv.conf, or 1 if no ndots
statement is present. Names with fewer dots are interpreted as relative names and will be searched
for in the domains listed in the search or domain directive in /etc/resolv.conf.
The number of UDP retries for a lookup can be changed with the -R option. number indicates how many
times host will repeat a query that does not get answered. The default number of retries is 1. If
number is negative or zero, the number of retries will default to 1.
Non-recursive queries can be made via the -r option. Setting this option clears the RD -- recursion
desired -- bit in the query which host makes. This should mean that the name server receiving the
query will not attempt to resolve name. The -r option enables host to mimic the behaviour of a name
server by making non-recursive queries and expecting to receive answers to those queries that are
usually referrals to other name servers.
By default host uses UDP when making queries. The -T option makes it use a TCP connection when
querying the name server. TCP will be automatically selected for queries that require it, such as
zone transfer (AXFR) requests.
The -4 option forces host to only use IPv4 query transport. The -6 option forces host to only use
IPv6 query transport.
The -t option is used to select the query type. type can be any recognised query type: CNAME, NS,
SOA, SIG, KEY, AXFR, etc. When no query type is specified, host automatically selects an appropriate
query type. By default it looks for A records, but if the -C option was given, queries will be made
for SOA records, and if name is a dotted-decimal IPv4 address or colon-delimited IPv6 address, host
will query for PTR records. If a query type of IXFR is chosen the starting serial number can be
specified by appending an equal followed by the starting serial number (e.g. -t IXFR=12345678).
The time to wait for a reply can be controlled through the -W and -w options. The -W option makes
host wait for wait seconds. If wait is less than one, the wait interval is set to one second. When
the -w option is used, host will effectively wait forever for a reply. The time to wait for a
response will be set to the number of seconds given by the hardware's maximum value for an integer
quantity.
The -s option tells host not to send the query to the next nameserver if any server responds with a
SERVFAIL response, which is the reverse of normal stub resolver behaviour.
The -m can be used to set the memory usage debugging flags record, usage and trace.
IDN SUPPORT
If host has been built with IDN (internationalized domain name) support, it can accept and display
non-ASCII domain names. host appropriately converts character encoding of domain name before sending
a request to DNS server or displaying a reply from the server. If you'd like to turn off the IDN
support for some reason, defines the IDN_DISABLE environment variable. The IDN support is disabled if
the variable is set when host runs.
FILES
/etc/resolv.conf
SEE ALSO
dig(1), named(8).
COPYRIGHT
Copyright (C) 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC")
Copyright (C) 2000-2002 Internet Software Consortium.
BIND9 Jun 30, 2000 HOST(1)
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