host - DNS lookup utility
host [ -aCdlnrTwv ] [ -c class ] [ -N ndots ] [ -R num-
ber ] [ -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
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 -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 implementations.
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)
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
dotted-decimal 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.
BIND9 Jun 30, 2000 2 [ Back ]