HOST(1) BIND 9 HOST(1)

NAME

host - DNS lookup utility

SYNOPSIS

host [-aACdlnrsTUwv] [-c class] [-N ndots] [-p port] [-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 by default performs 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 This option specifies that only IPv4 should be used for query
transport. See also the -6 option.

-6 This option specifies that only IPv6 should be used for query
transport. See also the -4 option.

-a The -a ("all") option is normally equivalent to -v -t ANY. It
also affects the behavior of the -l list zone option.

-A The -A ("almost all") option is equivalent to -a, except that
RRSIG, NSEC, and NSEC3 records are omitted from the output.

-c class
This option specifies the query class, which can be used to
lookup HS (Hesiod) or CH (Chaosnet) class resource records.
The default class is IN (Internet).

-C This option indicates that named should check consistency,
meaning that host queries 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 This option prints debugging traces, and is equivalent to the
-v verbose option.

-l This option tells named to list the zone, meaning 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
This option specifies the number of dots (ndots) 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 are searched for in the
domains listed in the search or domain directive in
/etc/resolv.conf.

-p port
This option specifies the port to query on the server. The
default is 53.

-r This option specifies a non-recursive query; setting this
option clears the RD (recursion desired) bit in the query.
This means that the name server receiving the query does 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
This option specifies the number of retries for UDP queries.
If number is negative or zero, the number of retries is
silently set to 1. The default value is 1, or the value of the
attempts option in /etc/resolv.conf, if set.

-s This option tells named 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.

-t type
This option specifies the 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 are made for
SOA records. If name is a dotted-decimal IPv4 address or
colon-delimited IPv6 address, host queries for PTR records.

If a query type of IXFR is chosen, the starting serial number
can be specified by appending an equals sign (=), followed by
the starting serial number, e.g., -t IXFR=12345678.

-T, -U This option specifies TCP or UDP. By default, host uses UDP
when making queries; the -T option makes it use a TCP
connection when querying the name server. TCP is automatically
selected for queries that require it, such as zone transfer
(AXFR) requests. Type ANY queries default to TCP, but can be
forced to use UDP initially via -U.

-m flag
This option sets memory usage debugging: the flag can be
record, usage, or trace. The -m option can be specified more
than once to set multiple flags.

-v This option sets verbose output, and is equivalent to the -d
debug option. Verbose output can also be enabled by setting
the debug option in /etc/resolv.conf.

-V This option prints the version number and exits.

-w This option sets "wait forever": the query timeout is set to
the maximum possible. See also the -W option.

-W wait
This options sets the length of the wait timeout, indicating
that named should wait for up to wait seconds for a reply. If
wait is less than 1, the wait interval is set to 1 second.

By default, host waits 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.

See also the -w option.

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 a domain name before
sending a request to a DNS server or displaying a reply from the
server. To turn off IDN support, define the IDN_DISABLE environment
variable. IDN support is disabled if the variable is set when host
runs.

FILES

/etc/resolv.conf

SEE ALSO

dig(1), named(8).

AUTHOR

Internet Systems Consortium

COPYRIGHT

2025, Internet Systems Consortium

9.18.34 2025-02-11 HOST(1)