DNS lookup utility
host command is a simple utility for
performing DNS lookups. It is normally used to convert names to IP addresses
and vice versa.
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
host should query instead of the server or
servers listed in /etc/resolv.conf.
The options are as follows:
- Use IPv4 only for query transport.
- Use IPv6 only for query transport.
- "All". The
-aoption is normally equivalent to
ANY. It also affects the behaviour of the
-llist zone option.
- Check consistency:
hostwill 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.
- Query class: This can be used to lookup
CH(Chaosnet) class resource records. The default class is
- Print debugging traces. Equivalent to the
- Obsolete. Use the IP6.INT domain for reverse lookups of IPv6 addresses as defined in RFC 1886 and deprecated in RFC 4159. The default is to use IP6.ARPA as specified in RFC 3596.
- List zone: The
hostcommand performs a zone transfer of zone name and prints out the NS, PTR and address records (A/AAAA).
-aoptions print all records in the zone.
- Memory usage debugging: the flag can be
trace. You can specify the
-moption more than once to set multiple flags.
- 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.
- 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.
- 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
hostto 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.
- Do not send the query to the next name server if any server responds with a SERVFAIL response, which is the reverse of normal stub resolver behavior.
- TCP: By default,
hostuses UDP when making queries. The
-Toption 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.
- Query type: The type argument can be any recognized
When no query type is specified,
hostautomatically selects an appropriate query type. By default, it looks for A, AAAA, and MX records. If the
-Coption is given, queries will be made for SOA records. If name is a dotted-decimal IPv4 address or colon-delimited IPv6 address,
hostwill query for PTR records.
If a query type of
IXFRis chosen, the starting serial number can be specified by appending an equal followed by the starting serial number (like
- Print the version number and exit.
- Verbose output. Equivalent to the
- Timeout: Wait for up to wait seconds for a reply. If
wait is less than one, the wait interval is set to
hostwill wait for 5 seconds for UDP responses and 10 seconds for TCP connections.
- Wait forever: The query timeout is set to the maximum possible.
Internet Systems Consortium, Inc.