host - DNS lookup utility
host [ -aCdlnrTwv ] [ -c class ] [ -N ndots ] [ -R number ] [ -t
type ] [ -W wait ] name [ server ]
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. The argument is provided for compatibility with
older implemementations. This option is equivalent to making a query of
type AXFR.
The -n option specifies that reverse lookups of IPv6 addresses should
use the IP6.INT domain and "nibble" labels as defined in RFC1886. The
default is to use IP6.ARPA and binary labels as defined in RFC2874.
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 -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 dotteddecimal
IPv4 address or colon-delimited IPv6 address, host will query
for PTR records.
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.
/etc/resolv.conf
dig(1), named(8).
BIND9 Jun 30, 2000 HOST(1)
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