nslookup(8)nslookup(8)NAMEnslookup - Queries Internet name servers interactively
SYNOPSIS
Noninteractive Mode
nslookup [-option ...] host-to-find [server]
Interactive Mode
nslookup [-option ...] [- server]
DESCRIPTION
The nslookup command is a program that is used to query Internet domain
name servers. The nslookup command has two modes: interactive and non‐
interactive. Noninteractive mode is used to print just the name and
requested information for a host or domain. Noninteractive mode is
invoked 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 hostname or address of a name server. 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. Interactive mode is
invoked when you specify nslookup without arguments (the default name
server will be used), or when the first argument you specify is a -
(dash) and the second argument is the hostname or Internet address of a
name server.
The options listed under the set command can be specified in the file
in the user's home directory if they are listed one per line. Options
can also be specified on the command line if they precede the arguments
and are prefixed with a - (dash). For example, to change the default
query type to host information, and the initial time-out to 10 seconds,
enter: nslookup -query=hinfo -timeout=10
Interactive Commands
Commands may be interrupted at any time by entering <Ctrl-c>. To exit,
enter <Ctrl-d> (EOF) or type exit. The command line length must be less
than 256 characters. To treat a built-in command as a hostname, pre‐
cede it with an escape character \ (backslash). Note that an unrecog‐
nized command will be interpreted as a hostname.
Looks 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 (dot) to the name. Changes 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 cannot be found, the names of servers that might
have the answer are returned. Changes the default server to the server
for the root of the domain name space. Currently, the host ns.inter‐
nic.net is used. (This command is a synonym for lserver ns.inter‐
nic.net.) The name of the root server can be changed with the set root
command. Connects with the finger server on the current host. The cur‐
rent host is defined when a previous lookup for a host was successful
and returned address information (see the set querytype=A command).
name is optional. The> and >> (redirection symbols) can be used to re‐
direct output in the usual manner. Lists the information available for
domain, optionally creating or appending to filename. The default out‐
put contains hostnames and their Internet addresses. option can be one
of the following: Lists all records of the specified type (see query‐
type later in this reference page). Lists aliases of hosts in the
domain. This option is a synonym for -t CNAME. Lists all records for
the domain. This option is a synonym for -t ANY. Lists CPU and oper‐
ating system information for the domain. This option is a synonym for
-t HINFO. Lists well-known services of hosts in the domain. This
option is a synonym for -t WKS. When output is directed to a file, #
(number signs) are printed for every 50 records received from the
server. Sorts and lists the output of previous ls command(s) with
more. Prints a brief summary of commands. Exits the program. This
command is used to change state information that affects the lookups.
Valid keywords are: Prints the current values of the frequently used
options to set. Information about the current default server and host
is also printed. Changes the query class to one of: The Internet
class. The Chaos class. The MIT Athena Hesiod class. Wildcard (any
of the above). The class specifies the protocol group of the informa‐
tion. (Default = IN, abbreviation = cl) Turns 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) Turns
exhaustive debugging mode on. Essentially all fields of every packet
are printed. (Default = nod2) Changes 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 com‐
ponents in its name. For example, if the default domain is CC.Berke‐
ley.EDU, the search list is CC.Berkeley.EDU and Berkeley.EDU. Use the
set srchlist command to specify a different list. Use the set all com‐
mand to display the list. (Default = value from hostname,
/etc/resolv.conf or LOCALDOMAIN, abbreviation = do) Changes the default
domain name to name1 and the domain search list to name1, name2, and so
on. A maximum of 6 names separated 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 dis‐
play the list. (Default = value based on hostname,
/etc/resolv.conf or LOCALDOMAIN, abbreviation = srchl) If set,
appends the default domain name to a single-component lookup
request (that is, one that does not contain a dot). (Default =
defname, abbreviation = [no]def) If the lookup request contains
at least one (dot) but does not end with a trailing dot, appends
the domain names in the domain search list to the request until
an answer is received. (Default = search, abbreviation =
[no]sea) Changes the default TCP/UDP name server port to value.
(Default = 53, abbreviation = po) Changes the type of informa‐
tion query to one of: The host's IPv4 address. The host's IPv6
address. The canonical name for an alias. The host CPU and
operating system type. The mailbox or mail list information.
The mail exchanger. The Naming AUthority PoinTeR that contains
rules for mapping parts of Uniform Resource Identifiers (URIs)
to domain names. The name server for the named zone. The host‐
name if the query is an Internet address; otherwise the pointer
to other information. The domain's start-of-authority informa‐
tion. The host that can provide a specific resolution service.
The text information. The user information. The supported
well-known services. Other types (ANY, AXFR, MB, MD, MF, NULL)
are described in the RFC1035 document. (Default = A, abbrevia‐
tions = q, ty) Tells the name server to query other servers if
it does not have the information. (Default = recurse, abbrevia‐
tion = [no]rec) Sets the number of retries to number. When a
reply to a request is not received within a certain amount of
time (changed with set time-out), 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, abbre‐
viation = ret) Changes the name of the root server to host.
This affects the root command. (Default = ns.internic.net.,
abbreviation = ro) Changes the initial timeout interval for
waiting for a reply to number seconds. Each retry doubles the
timeout period. (Default = 5 seconds, abbreviation = ti) Always
use a virtual circuit when sending requests to the server.
(Default = novc, abbreviation = [no]v) Ignore packet truncation
errors. (Default = noignoretc, abbreviation = [no]ig)
EXIT STATUS
In noninteractive mode, nslookup can return the following values: A
match was found. No match was found, or an error occurred.
ERRORS
If the lookup request was not successful, an error message is printed.
Possible errors are: 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 name server is
running on the server machine. The server does not have resource
records of the current query type for the host, although the hostname
is valid. The query type is specified with the set querytype command.
The host or domain name does not exist. The connection to the name or
finger server could not be made at the current time. This error com‐
monly occurs with ls and finger requests. The name server found an
internal inconsistency in its database and could not return a valid
answer. The name server refused to service the request. The name
server found that the request packet was not in the proper format. It
may indicate an error in nslookup.
FILES
Specifies the command path Initial domain name and name server
addresses User's initial options Summary of commands
SEE ALSO
Commands: named(8)
Functions: resolver(4)
Files: resolv.conf(4)
Specifications: RFC1034, RFC1035
nslookup(8)