NAME
host - DNS lookup utility
SYNOPSIS
host
[-aCdlnrsTwv] [-c class]
[-N ndots] [-R number]
[-t type] [-W wait]
[-m flag] [-4] [-6] [-v]
[-V] {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.
OPTIONS
-4
Use IPv4 only for query transport. See also
the -6 option.
-6
Use IPv6 only for query transport. See also
the -4 option.
-a
"All". The -a option is
normally equivalent to -v -t ANY. It also affects the behaviour
of the -l list zone option.
-c
class
Query class: This can be used to lookup HS
(Hesiod) or CH (Chaosnet) class resource records. The default class is IN
(Internet).
-C
Check consistency: host will query 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.
-d
Print debugging traces. Equivalent to the
-v verbose option.
-i
Obsolete. Use the IP6.INT domain for reverse
lookups of IPv6 addresses as defined in RFC1886 and deprecated in RFC4159. The
default is to use IP6.ARPA as specified in RFC3596.
-l
List zone: The
host command performs a
zone transfer of zone
name and prints out the NS, PTR and address
records (A/AAAA).
Together, the
-l -a options print all records in the zone.
-N
ndots
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.
-r
Non-recursive query: Setting this option
clears the RD (recursion desired) bit in the query. This should mean that the
name server receiving the query will not attempt to resolve name. The
-r option enables host to mimic the behavior of a name server by
making non-recursive queries and expecting to receive answers to those queries
that can be referrals to other name servers.
-R
number
Number of retries for UDP queries: If
number is negative or zero, the number of retries will default to 1.
The default value is 1.
-s
Do not send the query to the next
nameserver if any server responds with a SERVFAIL response, which is the
reverse of normal stub resolver behavior.
-t
type
Query type: The
type argument can be
any recognized query type: CNAME, NS, SOA, TXT, DNSKEY, AXFR, etc.
When no query type is specified,
host automatically selects an
appropriate query type. By default, it looks for A, AAAA, and MX records. If
the
-C option is given, queries will be made for SOA records. 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 (like
-t
IXFR=12345678).
-T
TCP: 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.
-m
flag
Memory usage debugging: the flag can be
record, usage, or trace. You can specify the -m
option more than once to set multiple flags.
-v
Verbose output. Equivalent to the -d
debug option.
-V
Print the version number and exit.
-w
Wait forever: The query timeout is set to the
maximum possible. See also the -W option.
-W
wait
Timeout: Wait for up to
wait seconds
for a reply. If
wait is less than one, the wait interval is set to one
second.
By default,
host will wait for 5 seconds for UDP responses and 10 seconds
for TCP connections.
See also the
-w option.
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).
AUTHOR
Internet Systems Consortium, Inc.
COPYRIGHT
Copyright © 2004, 2005, 2007-2009, 2014-2016 Internet Systems Consortium,
Inc. ("ISC")
Copyright © 2000-2002 Internet Software Consortium.