nslookup(1M) TCP/IP 5.4.2 nslookup(1M)
NAME
nslookup - query name servers interactively
SYNOPSIS
nslookup [ hosttofind | - [ servertouse ]]
DESCRIPTION
Use the nslookup command to query domain name servers. The nslookup
command has two modes: interactive and non-interactive. When you use
nslookup in interactive mode, it allows you to query the name server
for information about various hosts or domains or print a list of
hosts in the domain. When you use nslookup in non-interactive mode,
it prints the Internet address of a specified hosttofind (which can
be a hostname or domain name). You can also specify which
servertouse to obtain the information.
Arguments
Enter interactive mode as follows:
a) Specify no command arguments (the default name server will be
used), or
b) Specify a hyphen (-) as the first argument and the hostname of a
name server as the second argument.
To enter non-interactive mode, specify the name of the host to be
looked up as the first argument. Optionally, specify a name server as
the second argument.
Interactive Commands
Once you enter interactive mode, nslookup presents the > prompt, at
which you can enter any one of nslookup's interactive commands. You
can interrupt interactive commands at any time by typing a control-C.
To exit, type a control-D (EOF). The command line length must be
less than 80 characters.
Note: An unrecognized interactive command will be interpreted as a
host name.
host [server]
Look up information for host using the current default server
or using server if it is specified.
server server
lserver server
Change the default server to server. You can fully qualify
the server if you wish. Lserver uses the initial server to
look up information about a domain while server uses the
current default server. If an authoritative answer can't be
found, the names of servers that might have the answer are
returned.
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root Changes the default server to the server for the root of the
domain name space. Currently, the server nic.ddn.mil. is
used. (This command is a synonym for the lserver
nic.ddn.mil.) The name of the root server can be changed with
the set root command.
ls domain [> filename]
ls domain [>> filename]
ls -a domain [> filename]
ls -a domain [>> filename]
ls -h domain [> filename]
ls -h domain [>> filename]
ls -d domain [> filename]
List the information available for domain. The default output
contains host names and their Internet addresses. The -a
option lists aliases of hosts in the domain. The -h option
lists CPU and operating system information for the domain.
The -d option lists all contents of a zone transfer. When
output is redirected to a file, hash marks are printed for
every 50 records received from the server. You must use a
space to separate the redirect operator from the output file
name.
view filename
Sorts and lists the output of previous ls command(s) with
more(1).
help
? Prints a brief summary of commands.
set keyword[=value]
This command is used to change state information that affects
the lookups. Valid keywords are:
all Prints the current values of the various options to
set. Information about the current default server and
host is also printed.
[no]debug
Turn debugging mode on. A lot more information is
printed about the packet sent to the server and the
resulting answer.
(Default = nodebug, abbreviation = [no]deb)
[no]d2 Turn exhaustive debugging mode on. Essentially all
fields of every packet are printed.
(Default = nod2)
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[no]defname
Append the default domain name to every lookup.
(Default = defname, abbreviation = [no]def)
[no]search
With defname, search for each name in parent domains of
the current domain.
(Default = search)
domain=name
Change the default domain name to name. The default
domain name is appended to all lookup requests if the
defname option has been set. The search list is set to
parents of the domain with at least two components in
their names.
(Default = value in hostname or /etc/resolv.conf,
abbreviation = do)
querytype=value
type=value
Change the type of information returned from a query to
one of:
SOA The start of authority for a domain
A The host's Internet address (the default)
CNAME The canonical name for an alias
HINFO The host CPU and operating system type
MB The mail box
MX The mail exchanger
MG The mail group member
MINFO The mailbox or mail list information
MR The mail rename domain name
NS Nameserver for the named zone.
(Abbreviation = q)
[no]recurse
Tell the name server to query other servers if it
does not have the information.
(Default = recurse, abbreviation = [no]rec)
retry=number
Set the number of retries to number. When a reply
to a request is not received within a certain amount
of time (changed with set timeout), the request is
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resent. The retry value controls how many times a
request is resent before giving up.
(Default = 2, abbreviation = ret)
root=host Change the name of the root server to host. This
affects the root command.
(Default = nic.ddn.mil., abbreviation = ro)
timeout=number
Change the time-out interval for waiting for a reply
to number seconds.
(Default = 10 seconds, abbreviation = t)
[no]vc Always use a virtual circuit when sending requests
to the server.
(Default = novc, abbreviation = [no]v)
DIAGNOSTICS
If the lookup request was not successful, an error message is
printed. Possible errors are:
Time-out
The server did not respond to a request after a certain amount
of time (changed with set timeout=value) and a certain number
of retries (changed with set retry=value).
No information
Depending on the query type set with the set querytype
command, no information about the host was available, though
the host name is valid.
Non-existent domain
The host or domain name does not exist.
Connection refused
The server is down or unreachable.
Network is unreachable
The connection to the name server could not be made at the
current time.
Server failure
The name server found an internal inconsistency in its
database and could not return a valid answer.
Refused
The name server refused to service the request.
The following error should not occur and it indicates a bug in the
program.
Format error
The name server found that the request packet was not in the
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proper format.
FILES
/etc/resolv.conf initial domain name and name server addresses.
SEE ALSO
named(1M), resolver(3C), resolv.conf(4).
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