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
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
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''
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). The 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
lists all records of the specified type (see querytype
-a lists aliases of hosts in the domain; synonym for ``-t
-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''.
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
? 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 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
(Default = nodebug; abbreviation = [no]deb)
[no]d2 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(1), /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(1),
/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
(Default = defname; abbreviation = [no]defname)
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
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 document.
(Default = A; abbreviations = q, ty)
Tell the name server to query other servers if it does
not have the information.
(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
(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 seconds. Each retry doubles the timeout
(Default = 5 seconds; abbreviation = ti)
[no]vc Always use a virtual circuit when sending requests to
(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
named(8), resolver(3), resolver(5); RFC-1034, ``Domain Names - Concepts
and Facilities''; RFC-1035, ``Domain Names - Implementation and
4th Berkeley Distribution June 24, 1990 4th Berkeley Distribution
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