HOST(1) BIND 9 HOST(1)
NAME
host - DNS lookup utility
SYNOPSIS
host [-aACdlnrsTUwv] [-c class] [-N ndots] [-p port] [-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 dot-
ted-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.
-A "Almost all". The -A option is equivalent to -a except RRSIG,
NSEC, and NSEC3 records are omitted from the output.
-c class
Query class: This can be used to lookup HS (Hesiod) or CH
(Chaosnet) class resource records. The default class is IN (In-
ternet).
-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.
-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 consid-
ered 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.
-p port
Specify the port on the server to query. The default is 53.
-r Non-recursive query: Setting this option clears the RD (recur-
sion 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, or the value of the attempts option in /etc/resolv.conf,
if set.
-s Do not send the query to the next nameserver if any server re-
sponds 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-de-
limited 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 se-
rial number (like -t IXFR=12345678).
-T; -U TCP/UDP: 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 re-
quire it, such as zone transfer (AXFR) requests. Type ANY
queries default to TCP but can be forced to UDP initially using
-U.
-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. Verbose out-
put can also be enabled by setting the debug option in /etc/re-
solv.conf.
-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. These defaults can be overridden
by the timeout option in /etc/resolv.conf.
See also the -w option.
IDN SUPPORT
If host has been built with IDN (internationalized domain name) sup-
port, it can accept and display non-ASCII domain names. host appropri-
ately converts character encoding of domain name before sending a re-
quest to DNS server or displaying a reply from the server. If you'd
like to turn off the IDN support for some reason, define the IDN_DIS-
ABLE 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
COPYRIGHT
2020, Internet Systems Consortium
9.16.4-Debian 2020-06-10 HOST(1)