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 or
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 unrecognized 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 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 command).
Name is optional. > and >> can be used to redirect output in the
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 -t HINFO.
-s lists well-known services of hosts in the domain. synonym for
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 keywords are:
all Prints the current values of the frequently-used options to
set. Information about the current default server and host is
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)
Turn exhaustive debugging mode on. Essentially all fields of
every packet are printed.
(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
Berkeley.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, abbreviation = 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. For example,
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, abbreviation = 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
(Default = A, abbreviations = q, ty)
Tell the name server to query other servers if it does not have
(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 controls 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
(Default = ns.internic.net., abbreviation = ro)
Change 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
(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 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 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 command.
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
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
$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(4), named(1M),
RFC-1034 ``Domain Names - Concepts and Facilities''
RFC-1035 ``Domain Names - Implementation and Specification''
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