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NSLOOKUP(8C)                                                      NSLOOKUP(8C)



NAME
       nslookup - query domain name servers interactively

SYNOPSIS
       nslookup [ -l ] [ address ]

DESCRIPTION
       nslookup  is  an  interactive  program  to  query  Internet domain name
       servers. The user can contact servers to request  information  about  a
       specific host or print a list of hosts in the domain.

OPTIONS
       -l       Use  the  local  host's  name server instead of the servers in
                /etc/resolv.conf.  (If /etc/resolv.conf does not exist or does
                not  contain  server  information, the -l option does not have
                any effect).

       address  Use the name server on the host machine with the given  Inter-
                net address.

USAGE
   Overview
       The  Internet  domain  name-space  is  tree-structured,  with top-level
       domains such as:

              COM    commercial establishments
              EDU    educational institutions
              GOV    government agencies
              MIL    MILNET hosts

       If you are looking for a specific host,  you  need  to  know  something
       about  the  host's  organization  in  order  to determine the top-level
       domain it belongs to.  For instance, if you want to find  the  Internet
       address of a machine at UCLA, do the following:

       o      Connect  with  the root server using the root command.  The root
              server of the name space has knowledge of the top-level domains.

       o      Since UCLA is a university, its domain name is  ucla.edu.   Con-
              nect  with  a  server  for  the ucla.edu domain with the command
              serverucla.edu.  The response will print the names of hosts that
              act  as servers for that domain.  Note: the root server does not
              have  information  about  ucla.edu,  but  knows  the  names  and
              addresses  of  hosts  that do.  Once located by the root server,
              all future queries will be sent to the UCLA name server.

       o      To request information about a particular  host  in  the  domain
              (for  instance,  locus),  just type the host name.  To request a
              listing of hosts in the UCLA domain, use the ls command.  The ls
              command  requires  a  domain name (in this case, ucla.edu) as an
              argument.

       Note: if you are connected with a name server that  handles  more  than
       one domain, all lookups for host names must be fully specified with its
       domain.   For  instance,  the   domain   harvard.edu   is   served   by
       seismo.css.gov,   which  also  services  the  css.gov  and  cornell.edu
       domains. A lookup request for the host aiken in the harvard.edu  domain
       must be specified as aiken.harvard.edu.  However, the

              set domain=name

       and

              set defname

       commands  can  be  used  to  automatically append a domain name to each
       request.

       After a successful lookup of a host, use the finger command to see  who
       is  on the system, or to finger a specific person.  To get other infor-
       mation about the host, use the

              set querytype=value

       command to change the type of information desired and  request  another
       lookup.  (finger requires the type to be A.)

   Commands
       Commands  may  be  interrupted  at any time by typing CTRL-C.  To exit,
       type CTRL-D (EOF).  The command line length must be less than 80  char-
       acters.   Note:  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 it is 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 `lserver sri-nic.arpa'.)  The name
              of the root server can be changed with the set root command.

       finger [ name]
              Connect with the finger server on the  current  host,  which  is
              defined  by  a  previous  successful lookup for a host's address
              information (see the set  querytype=A  command).   As  with  the
              shell, output can be redirected to a named file using >> and >>>>.

       "ls [-ah]
              List  the  information available for domain.  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.   As  with  the
              shell,  output can be redirected to a named file using >> and >>>>.
              When output is directed to a file, hash marks  are  printed  for
              every 50 records received from the server.

       viewfilename
              Sort and list the output of the ls command with more(1).

       help

       ?      Print a brief summary of commands.

       setkeyword [ = 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]deb[ug]
                     Turn debugging mode on. A lot more information is printed
                     about  the  packet  sent  to the server and the resulting
                     answer.  The default is nodebug.

              [no]def[name]
                     Append the default domain  name  to  every  lookup.   The
                     default is nodefname.

              do[main]=filename
                     Change  the default domain name to filename.  The default
                     domain name is appended to all lookup requests if defname
                     option  has  been  set.   The  default  is  the  value in
                     /etc/resolv.conf.

              q[querytype]=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.
                     MB     The mailbox domain name.
                     MG     The mail group member.
                     MINFO  The mailbox or mail list information.

                     (Other  types specified in the RFC883 document are valid,
                     but are not very useful.)

              [no]recurse
                     Tell the name server to query other servers  if  it  does
                     not have the information.  The default is recurse.

              ret[ry]=count
                     Set  the number of times to retry a request before giving
                     up to count.  When a reply to a request is  not  received
                     within  a  certain amount of time (changed with set time-
                     out), the request is resent.  The default is count is 2.

              ro[ot]=host
                     Change the name of the root server to host.  This affects
                     the  root  command.   The  default  root  server  is sri-
                     nic.arpa.

              t[timeout]=interval
                     Change the time-out for a reply to interval seconds.  The
                     default interval is 10 seconds.

              [no]v[c]
                     Always use a virtual circuit when sending requests to the
                     server.  The default is novc.

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 pro-
       gram.

       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.

SEE ALSO
       resolver(3), resolv.conf(5), named(8C),

       RFC 1034, RFC 1035

                                 30 June 1989                     NSLOOKUP(8C)