host(1) - phpMan

HOST(1) BIND9 HOST(1)

NAME
host - DNS lookup utility

SYNOPSIS
host [-aCdlnrsTUwv] [-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, 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 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, -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 require 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 output can also be enabled
by setting the debug option in /etc/resolv.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.