nslookup(1M) nslookup(1M)
NAME
nslookup - query Internet name servers interactively
SYNOPSIS
nslookup [-option ...] [host-to-find | - [server]]
DESCRIPTION
nslookup is a program to query Internet domain name servers. nslookup
has two modes: interactive and non-interactive. Interactive mode
allows the user to query name servers for information about various
hosts and domains or to print a list of hosts in a domain. Non-inter-
active mode is used to print just the name and requested information
for a host or domain.
ARGUMENTS
Interactive mode is entered in the following cases:
a) when no arguments are given (the default name server will be
used),
b) when the first argument is a hyphen (-) and the second argument is
the host name or Internet address of a name server.
Non-interactive mode is used when the name or Internet address of the
host to be looked up is given as the first argument. The optional
second argument specifies the host name or address of a name server.
The options listed under the set command below can be specified in the
.nslookuprc file in the user's home directory if they are listed one
per line. Comment lines start with a semicolon (;).
Options can also be specified on the command line if they precede the
arguments and are prefixed with a hyphen. For example, to change the
default query type to host information, and the initial timeout to 10
seconds, type:
nslookup -query=hinfo -timeout=10
INTERACTIVE COMMANDS
Commands may be interrupted at any time by typing Ctrl-C. To exit,
type Ctrl-D (EOF) or type exit. The command line length must be less
than 256 characters. To treat a built-in command as a host name, pre-
cede it with an escape character (\). Note: an unrecognized command
will be interpreted as a host name.
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host [server]
Look up information for host using the current default server or
using server if specified. If host is an Internet address and the
query type is A or PTR, the name of the host is returned. If host
is a name and does not have a trailing period, the default domain
name is appended to the name. (This behavior depends on the state
of the set options domain, srchlist, defname, and search). To
look up a host not in the current domain, append a period to the
name.
server domain
lserver domain
Change the default server to domain. lserver uses the initial
server to look up information about 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.
root Changes the default server to the server for the root of the
domain name space. Currently, the host ns.nic.ddn.mil is used.
(This command is a synonym for lserver ns.nic.ddn.mil.) The name
of the root server can be changed with the set root command.
finger [name] [> filename]
finger [name] [>> filename]
Connects with the finger server on the current host. The current
host is defined when a previous lookup for a host was successful
and returned address information. (See the set querytype=A com-
mand). name is optional. > and >> can be used to redirect output
in the usual manner.
ls [option] domain [> filename]
ls [option] domain [>> filename]
List the information available for domain, optionally creating or
appending to filename. The default output contains host names and
their Internet addresses. option can be one of the following:
-t querytype
Lists all records of the specified type (see querytype
below).
-a Lists aliases of hosts in the domain. Synonym for -t CNAME.
-d Lists all records for the domain. Synonym for -t ANY.
-h Lists CPU and operating system information for the domain.
Synonym for -t HINFO.
-s Lists well-known services of hosts in the domain. Synonym
for -t WKS.
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When output is directed to a file, hash marks are printed for
every 50 records received from the server.
view filename
Sorts and lists the output of previous ls command(s) with
more(1).
help
? Prints a brief summary of commands.
exit Exits the program.
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 frequently-used options to
set. Information about the current default server and host
is also printed.
class=value
Change the query class to one of:
IN the Internet class
CHAOS the Chaos class
HESIOD the MIT Athena Hesiod class
ANY wildcard (any of the above)
The class specifies the protocol group of the information.
Default = IN, abbreviation = cl.
[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.
domain=name
Change the default domain name to name. The default domain
name is appended to a lookup request depending on the state
of the defname and search options. The domain search list
contains the parents of the default domain if it has at
least two components in its name. For example, if the
default domain is CC.Berkeley.EDU, the search list is
CC.Berkeley.EDU and Berkeley.EDU. Use the set srchlist com-
mand to specify a different list. Use the set all command to
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display the list. Default = value from hostname,
/etc/resolv.conf, or LOCALDOMAIN; abbreviation = do.
srchlist=name1/name2/...
Change the default domain name to name1 and the domain
search list to name1, name2, etc. A maximum of 6 names sepa-
rated by slashes (/) can be specified. For example,
set srchlist=lcs.MIT.EDU/ai.MIT.EDU/MIT.EDU
sets the domain to lcs.MIT.EDU and the search list to the
three names. This command overrides the default domain name
and search list of the set domain command. Use the set all
command to display the list. Default = value based on host-
name, /etc/resolv.conf, or LOCALDOMAIN; abbreviation =
srchl.
[no]defname
If set, append the default domain name to a single-component
lookup request (i.e., one that does not contain a period).
Default = defname, abbreviation = [no]def.
[no]search
If the lookup request contains at least one period but
doesn't end with a trailing period, append the domain names
in the domain search list to the request until an answer is
received. Default = search, abbreviation = [no]sea.
port=value
Change the default TCP/UDP name server port to value.
Default = 53, abbreviation = po.
query[type]=value
type=value
Change the type of information query to one of:
A the host's Internet address
ANY all information
CNAME the canonical name for an alias
HINFO the host CPU and operating system type
MINFO the mailbox or mail list information
MX the mail exchanger
NS the name server for the named zone
PTR the host name if the query is an Internet address,
otherwise the pointer to other information
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SOA the domain's "start-of-authority" information
TXT the text information
UINFO the user information
WKS the supported well-known services (IP protocol
number and port)
Other types (AXFR, MB, MD, MF, NULL) are described in the
RFC-1035 document. Default = A, abbreviations = q, ty.
[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 timeout period is doubled
and the request is resent. The retry value controls how many
times a request is resent before giving up. Default = 4,
abbreviation = ret.
root=host
Change the name of the root server to host. This affects the
root command. Default = ns.nic.ddn.mil., abbreviation = ro.
timeout=number
Change the initial timeout interval for waiting for a reply
to number seconds. Each retry doubles the timeout period.
Default = 5 seconds, abbreviation = ti.
[no]vc
Always use a virtual circuit when sending requests to the
server. Default = novc, abbreviation = [no]v.
[no]ignoretc
Ignore packet truncation errors. Default = noignoretc,
abbreviation = [no]ig.
DIAGNOSTICS
If the lookup request was not successful, an error message is printed.
Possible errors are:
Timed 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).
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No response from server
No name server is running on the server machine.
No records
The server does not have resource records of the current query
type for the host, although the host name is valid. The query
type is specified with the set querytype command.
Non-existent domain
The host or domain name does not exist.
Connection refused
Network is unreachable
The connection to the name or finger server could not be made at
the current time. This error commonly occurs with ls and finger
requests.
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.
Format error
The name server found that the request packet was not in the
proper format. It may indicate an error in nslookup.
ENVIRONMENT
HOSTALIASES
file containing host aliases
LOCALDOMAIN
overrides default domain
FILES
/etc/resolv.conf
initial domain name and name server addresses
$HOME/.nslookuprc
user's initial options
/usr/lib/named/nslookup.help
summary of commands
/usr/lib/named/bog.ascii
/usr/lib/named/bog.ps
Name Server Operations Guide for BIND ("BOG"); ASCII and
PostScript format
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SEE ALSO
named(1M), resolver(3N), resolv.conf(4).
RFC-1034 Domain Names - Concepts and Facilities
RFC-1035 Domain Names - Implementation and Specification
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