illumos: manual page: host.1

HOST(1) BIND9 HOST(1)

NAME

host - DNS lookup utility

SYNOPSIS

host [-aCdlnrsTwv] [-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.

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. Transfer the zone printing out the NS, PTR and
address records (A/AAAA). If combined with -a all records will be
printed.

The -i option specifies that reverse lookups of IPv6 addresses should use
the IP6.INT domain as defined in RFC1886. The default is to use IP6.ARPA.

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 behavior
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 -4 option forces host to only use IPv4 query transport. The -6 option
forces host to only use IPv6 query transport.

The -t option is used to select the query type. type can be any
recognized 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, AAAA, and MX 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. 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 (e.g. -t IXFR=12345678).

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.

The -s option tells host not to send the query to the next nameserver if
any server responds with a SERVFAIL response, which is the reverse of
normal stub resolver behavior.

The -m can be used to set the memory usage debugging flags record, usage
and trace.

The -V option causes host to print the version number and exit.

IDN SUPPORT

If host has been built with IDN (internationalized domain name) support,
it can accept and display non-ASCII domain names. host appropriately
converts character encoding of domain name before sending a request to
DNS server or displaying a reply from the server. If you'd like to turn
off the IDN support for some reason, defines the IDN_DISABLE environment
variable. The IDN support is disabled if the variable is set when host
runs.

FILES

/etc/resolv.conf

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