nslookup - query Internet name servers interactively
nslookup [ -option ... ] [ host-to-find | - [ server ]]
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-interactive mode is used to print just the name and requested information for a host
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. 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
Commands may be interrupted at any time by typing a control-C. To exit, type a control-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, precede it with an escape character (\). N.B. an unrec-
ognized command will be interpreted as a host name.
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.
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.internic.net is used. (This command is a synonym for
lserver ns.internic.net.) The name of the root server can be changed with the set
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 command). Name is optional. > and >> can be used to re-
direct 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:
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
-s lists well-known services of hosts in the domain. synonym for -t WKS.
When output is directed to a file, hash marks are printed for every 50 records
received from the server.
Sorts and lists the output of previous ls command(s) with more(1).
? Prints a brief summary of commands.
exit Exits the program.
This command is used to change state information that affects the lookups. Valid
all Prints the current values of the frequently-used options to set. Informa-
tion about the current default server and host is also printed.
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)
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
(Default = nod2)
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 Berke-
ley.EDU. Use the set srchlist command to specify a different list. Use the
set all command to display the list.
(Default = value from hostname, /etc/resolv.conf or LOCALDOMAIN, abbrevia-
tion = do)
Change the default domain name to name1 and the domain search list to name1,
name2, etc. A maximum of 6 names separated by slashes (/) can be specified.
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 hostname, /etc/resolv.conf or LOCALDOMAIN, abbre-
viation = srchl)
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)
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)
Change the default TCP/UDP name server port to value.
(Default = 53, abbreviation = po)
Change the type of information query to one of:
A the host's Internet address.
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.
SOA the domain's ``start-of-authority'' information.
TXT the text information.
UINFO the user information.
WKS the supported well-known services.
Other types (ANY, AXFR, MB, MD, MF, NULL) are described in the RFC-1035 doc-
(Default = A, abbreviations = q, ty)
Tell the name server to query other servers if it does not have the informa-
(Default = recurse, abbreviation = [no]rec)
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 con-
trols how many times a request is resent before giving up.
(Default = 4, abbreviation = ret)
Change the name of the root server to host. This affects the root command.
(Default = ns.internic.net., abbreviation = ro)
Change the initial timeout interval for waiting for a reply to number sec-
onds. 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)
Ignore packet truncation errors.
(Default = noignoretc, abbreviation = [no]ig)
If the lookup request was not successful, an error message is printed. Possible errors
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 response from server
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 host name is valid. The query type is specified with the set querytype
The host or domain name does not exist.
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.
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.
/etc/resolv.conf initial domain name and
name server addresses.
$HOME/.nslookuprc user's initial options.
/usr/share/misc/nslookup.help summary of commands.
HOSTALIASES file containing host aliases.
LOCALDOMAIN overrides default domain.
resolver(3), resolver(5), named(8),
RFC-1034 ``Domain Names - Concepts and Facilities''
RFC-1035 ``Domain Names - Implementation and Specification''
4.3 Berkeley Distribution June 24, 1990 NSLOOKUP(8)