4.21. host - DNS lookup utility

4.21.1. Synopsis

host [-a] [-C] [-d] [-l] [-n] [-r] [-s] [-T] [-w] [-v] [-c <class>] [-N <num-dots>] [-R <number>] [-t <type>] [-W <num-seconds>] [-m <flag>] [[-4] | [-6]] [-v] [-V] <name> [<server>]

4.21.2. 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 nameserver that host should query instead of the server or servers listed in /etc/resolv.conf.

Warning

This program may be removed from the Loop distribution in the future. Please use dig(1) instead.

4.21.3. 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

Stands for "all". The -a option is normally equivalent to -v -tANY. It also affects the behaviour of the -l list zone option.

-c <class>

Set the query class. The default class is IN (Internet). Other usable classes are HS (Hesiod) or CH (Chaosnet).

-C

Check consistency. host will query the SOA records for zone <name> from all the listed authoritative nameservers for that zone. The list of nameservers is defined by the NS records that are found for the zone.

-d

Print debugging traces. Equivalent to the -v option.

Error

TODOMUKS: Combine -d and -v.

-i

Do reverse IPv6 lookups using the obsolete RFC 1886 IP6.INT domain, which is no longer in use. Obsolete bit string label queries (RFC 2874) are not attempted.

Error

TODOMUKS: Remove this option.

-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 <num-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 DNS message header flag in the query. This should mean that the nameserver receiving the query will not attempt to resolve <name>. The -r option enables host to mimic the behavior of a nameserver by making non-recursive queries and expecting to receive answers to those queries that can be referrals to other nameservers.

-R <count>

Number of retries for UDP queries. If <count> is less than 1, it will be set to 1. The default value is 1.

-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>

Specifies the record type. The <type> argument can be any recognized RR 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

Use TCP. By default, host uses UDP when making queries. The -T option makes it use a TCP connection when querying the nameserver. TCP will be automatically selected for queries that require it, such as zone transfer (AXFR) requests.

-v

Print debugging traces. Equivalent to the -d option.

Error

TODOMUKS: Combine -d and -v.

-V

Print the program's version and exit.

-w

Wait forever: The query timeout is set to the maximum possible. See also the -W option.

-W <num-seconds>

Timeout: Wait for up to <num-seconds> seconds for a reply. If <num-seconds> is less than 1, the wait interval is set to 1 second.

By default, host will wait for 5 seconds for UDP responses and 10 seconds for TCP connections.

Also see the -w option.

4.21.4. Files

/etc/resolv.conf

4.21.5. See also

dig(1), named(8)