host
—
DNS lookup utility
host |
[ -aCdilrsTvw46 ]
[-c
class ]
[-N
ndots ]
[-R
number ]
[-t
type ]
[-W
wait ]
name
[server ] |
host
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.
When
name is not provided,
host
prints a short summary of it's usage.
server is an optional argument which is either
a domain name or an IP address of the name server that
host
should query instead of the server or
servers listed in
/etc/resolv.conf. When
server is a domain name, system resolver is
used to obtain it's address.
Supported options:
-a
- Make a verbose query of type
ANY
.
Equivalent to -v
-t
ANY
.
-C
- 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
name.
-c
class
- Perform DNS query of class class.
Recognized classes are
IN
(Internet),
CH
(Chaosnet),
HS
(Hesiod),
NONE
,
ANY
and
CLASS
N
(where N is a number from 1 to 255).
Default is IN
.
-d
- Produce verbose output. This is a synonym for
-v
, and is provided for backward
compatibility.
-i
- 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
used.
-l
- List all
NS, PTR, A
and
AAAA
records in zone
name by performing a zone transfer
(AXFR
). You can combine this option
with -a
to print all records, or with
-t
to only print specific ones.
-N
ndots
- Consider names with at least this many dots as absolute. That is, try to
resolve them directly before consulting
domain
or
search
options from
/etc/resolv.conf.
-r
- Perform non-recursive query to the name server by clearing RD
(“recursion desired”) bit of the query.
-R
number
- 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.
-s
- Report SERVFAIL responses as they are, do not ignore them.
-T
- Query name server over TCP. By default UDP is used, except for
AXFR
and
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).
-t
type
- Perform DNS query of type type, which can
be any standard query type name (
A
,
CNAME
,
MX
,
TXT
, etc), a
wildcard query (ANY
), or
TYPE
N,
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. -t
IXFR
=12345678).
The default is to query for A
,
AAAA
, and
MX
records, unless
-C
or
-l
options are given (in which case
SOA
or
AXFR
queries are made) or
name is a valid IP address (in which case
reverse lookup using PTR
query is
performed).
-v
- Produce verbose output.
-w
- Wait forever (or for a very long time) for response from the name
server.
-W
wait
- 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
-R
).
-4
- Only use IPv4 transport.
-6
- Only use IPv6 transport.
/etc/resolv.conf
drill(1),
resolv.conf(5)
host
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 (
-D
and -m
) are not
supported.
- Query class
CLASS0
and type
TYPE0
are not supported.
- Backslashes in domain names are treated especially.
- The maximum of 255 retries (option
-R
)
are supported.
- Some resource records are formatted differently. For example,
RRSIG
and
DNSKEY
records are displayed without
spaces in them.
- When parsing /etc/resolv.conf commands
sortlist
and
options
are ignored. When multiple
search
and/or
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
last.
- ‘Pseudosection TSIG’ is missing from verbose packet
output.
Vitaly Magerya
⟨magv@tx97.net⟩