NSLOOKUP(1)

NAME
nslookup - query name servers interactively

SYNOPSIS
nslookup [ -option ... ] [ host-to-find | - [ server ]]

DESCRIPTION
Nslookup is a program to query DARPA Internet domain name servers. Nslookup has two modes: interactive and non-interactive. Interactive mode allows the user to query the name server for information about various hosts and domains or print a list of hosts in the domain. Non-interactive mode is used to print just the name and Internet address of 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 hostname or Internet address of a name server.

Non-interactive mode is used when the name of the host to be looked up is given as the first argument. The optional second argument specifies the hostname or Internet address of a name server.

The options listed under the ``set'' command below can 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 default timeout to 10 seconds, type:

    nslookup -query=hinfo -timeout=10

INTERACTIVE COMMANDS
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 80 characters. N.B. an unrecognized command will be interpreted as a host name.

host [server]
    Look up information for host using the current default server or using server if specified.

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 sri-nic.arpa is used. (This command is a synonym for the lserver sri-nic.arpa.) 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 usual manner.

ls domain [> filename]

ls domain [>> filename]

ls -a domain [> filename]

ls -a domain [>> filename]

ls -h domain [> filename]

ls -h domain [>> filename]

ls -d domain [> filename]

ls -d domain [>> filename]
    List the information available for domain, optionally creating or appending to filename. The default output contains host names and their Internet addresses. The -a option lists aliases of hosts in the domain. The -h option lists CPU and operating system information for the domain. The -d option lists all contents of a zone transfer. 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 various options to set. Information about the current default server and host is also printed.

    [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)

    [no]defname
        Append the default domain name to every lookup.
        (Default = defname, abbreviation = [no]def)

    [no]search
        With defname, search for each name in parent domains of the current domain.
        (Default = search)

    domain=name
        Change the default domain name to name. The default domain name is appended to all lookup requests if the defname option has been set. The search list is set to parents of the domain with at least two components in their names.
        (Default = value in hostname or /etc/resolv.conf, abbreviation = do)

    querytype=value

    type=value
        Change the type of information returned from a query to one of:

        A   the host's Internet address (the default).

        CNAME
            the canonical name for an alias.

        HINFO
            the host CPU and operating system type.

        MD  the mail destination.

        MX  the mail exchanger.

        MG  the mail group member.

        MINFO
            the mailbox or mail list information.

        MR  the mail rename domain name.

        NS  nameserver for the named zone.
    Other types specified in the RFC-1035 document are valid but aren't very useful.
    (Abbreviation = q)

    [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 request is resent. The retry value controls how many times a request is resent before giving up.
        (Default = 2, abbreviation = ret)

    root=host
        Change the name of the root server to host. This affects the root command.
        (Default = sri-nic.arpa, abbreviation = ro)

    timeout=number
        Change the time-out interval for waiting for a reply to number seconds.
        (Default = 10 seconds, abbreviation = t)

    [no]vc
        Always use a virtual circuit when sending requests to the server.
        (Default = novc, abbreviation = [no]v)

DIAGNOSTICS
If the lookup request was not successful, an error message is printed. Possible errors are:

Time-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).

No information
    Depending on the query type set with the set querytype command, no information about the host was available, though the host name is valid.

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 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.

The following error should not occur and it indicates a bug in the program.

Format error
    The name server found that the request packet was not in the proper format.

FILES
/etc/resolv.conf    initial domain name and name server addresses.
/usr/local/nslookup.help    summary of commands.

SEE ALSO
resolver(3), resolver(5), named(8),
RFC-1034 ``Domain Names - Concepts and Facilities''
RFC-1035 ``Domain Names - Implementation and Specification''

AUTHOR
Andrew Cherenson