# host

host
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## 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`.

## 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

  TCP: 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.

-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`.

  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 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`

## SEE ALSO

dig(1) , named(8) .

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