DNS lookup utility
is a simple utility for performing DNS
lookups. It is normally used to convert names to IP addresses and vice versa.
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
will by default
perform a reverse lookup for that address.
is not provided,
prints a short summary of it's usage.
is an optional argument which is either
a domain name or an IP address of the name server that
should query instead of the server or
servers listed in /etc/resolv.conf
is a domain name, system resolver is
used to obtain it's address.
- Make a verbose query of type
- Query for
SOA records for zone
name from all of it's authoritative name
servers. The list of name servers is obtained via
NS query for
- Perform DNS query of class class.
Recognized classes are
(where N is a number from 1 to 255).
- Produce verbose output. This is a synonym for
-v, and is provided for backward
- Use IP6.INT domain for reverse lookups of IPv6 addresses (as defined in
RFC1886; note that RFC4159 deprecates IP6.INT). By default IP6.ARPA is
- List all
NS, PTR, A and
AAAA records in zone
name by performing a zone transfer
AXFR). You can combine this option
-a to print all records, or with
-t to only print specific ones.
- Consider names with at least this many dots as absolute. That is, try to
resolve them directly before consulting
search options from
- Perform non-recursive query to the name server by clearing RD
(“recursion desired”) bit of the query.
- Retry this many times when a query does not receive an answer in time. The
default is 1 retry. If number is negative
or zero, 1 is used instead.
- Report SERVFAIL responses as they are, do not ignore them.
- Query name server over TCP. By default UDP is used, except for
IXFR queries, which require TCP.
host will also retry UDP queries in TCP
mode if the UDP response was truncated (i.e. had TC bit set).
- Perform DNS query of type type, which can
be any standard query type name (
TXT, etc), a
wildcard query (
where N is a number from 1 to 65535. For
IXFR (incremental zone transfer)
queries the starting serial number can be specified by appending an equal
sign followed by the number (e.g.
The default is to query for
MX records, unless
-l options are given (in which case
AXFR queries are made) or
name is a valid IP address (in which case
reverse lookup using
PTR query is
- Produce verbose output.
- Wait forever (or for a very long time) for response from the name
- Wait this many seconds for a reply from name server before timing out. If
wait is negative or zero, value of 1 is
used. The default is to wait 10 seconds for TCP connections, and 5 seconds
for UDP (both are subject to retries, see option
- Only use IPv4 transport.
- Only use IPv6 transport.
aims to be reasonably compatible with
‘host’ utility from BIND9 distribution, both in supported
options and in produced output. Here is a list of known notable differences:
- Debugging options (
-m) are not
- Query class
CLASS0 and type
TYPE0 are not supported.
- Backslashes in domain names are treated especially.
- The maximum of 255 retries (option
- Some resource records are formatted differently. For example,
DNSKEY records are displayed without
spaces in them.
- When parsing /etc/resolv.conf commands
options are ignored. When multiple
domain commands are present,
host first uses the last
domain command, and then all of
search commands, while
‘host’ from BIND9 uses whatever command was specified
- ‘Pseudosection TSIG’ is missing from verbose packet