host

host
+Prev	Manual pages	Next +

+ + + + + +

Name

+ host + — DNS lookup utility +

+ + + +

Synopsis

+ host + [-aCdlnrsTUwv] + [-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, -U +

+ TCP/UDP: + 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. Type ANY queries default + to TCP but can be forced to UDP initially using -U. +

-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 +

+ +

+Prev	Up	Next +
+mdig	Home	delv