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NAME    [Toc]    [Back]

     nslookup - query Internet name servers interactively

SYNOPSIS    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

     Nslookup is a program to query Internet domain name servers.

Nslookup    [Toc]    [Back]

     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 domain.

ARGUMENTS    [Toc]    [Back]

     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 controlC.  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
     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.  If host is an Internet
address and
              the query type is A or PTR, the name of the host is
              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.

     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.

     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 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 resulting

                       (Default   =   nodebug;   abbreviation   =

              [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
                       the search  list  is  CC.Berkeley.EDU  and
                       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,

                             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 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
                       a period).

                       (Default   =   defname;   abbreviation   =

                       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

                       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 document.

                       (Default = A; abbreviations = q, ty)

                       Tell   the  name  server  to  query  other
servers if it does
                       not have the information.

                       (Default   =   recurse;   abbreviation   =

                       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
                       the server.

                       (Default = novc; abbreviation = [no]v)

FILES    [Toc]    [Back]

     /etc/resolv.conf     initial domain name and name server addresses

DIAGNOSTICS    [Toc]    [Back]

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

     Timed 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 response from server
            No name server is running on the server machine.

     No records
            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.

     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 ls
and finger

     Server failure
            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.

     Format error
            The name server found that the request packet was not
in the proper
 format.  It may indicate an error in nslookup.

SEE ALSO    [Toc]    [Back]

     dig(1), resolver(3), resolver(5), named(8)

     RFC 1034   Domain Names - Concepts and Facilities
     RFC 1035   Domain Names - Implementation and Specification

AUTHORS    [Toc]    [Back]

     Andrew Cherenson

OpenBSD     3.6                           June      24,      1990
[ Back ]
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