NAME

host — DNS lookup utility

SYNOPSIS

host [-46aCdilrsTVvw] [-c class] [-m flag] [-N ndots] [-R number] [-t type] [-W wait] name [server]

DESCRIPTION

The host command is a simple utility for performing DNS lookups. It is normally used to convert names to IP addresses and vice versa.

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 options are as follows:

-4

Use IPv4 only for query transport.

-6

Use IPv6 only for query transport.

-a

"All". The -a option is normally equivalent to -v -t ANY. It also affects the behaviour of the -l list zone option.

-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.

-c class

Query class: This can be used to lookup HS (Hesiod) or CH (Chaosnet) class resource records. The default class is IN (Internet).

-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.

-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.

-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 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.

-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.

-s

Do not send the query to the next name server if any server responds with a SERVFAIL response, which is the reverse of normal stub resolver behavior.

-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.

-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).

-V