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 nslookup(1)							 nslookup(1)




 NAME
      nslookup - query name servers interactively

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

      nslookup [-option ...] [- [server]]

 DESCRIPTION
      nslookup is a program to query Internet domain name servers.  nslookup
      has been extended to follow the configured name resolution algorithm
      of the host and to query NIS, as well as, DNS and host tables.

      Both an interactive and non-interactive mode are available with
      nslookup.	 Interactive mode allows the user to query a name server for
      information about various hosts and domains, or print a list of hosts
      in the domain.  Non-interactive mode is used to query a name server
      for information about one host or domain.

      By default, nslookup accesses name services for name and address
      resolution based on the policy information obtained from the switch
      configuration file /etc/nsswitch.conf.  When the policy is set to use
      NIS or /etc/hosts first, or when DNS is first but unavailable, then
      nslookup will only provide a limited command set (a help command while
      in this situation will show what actions are possible when querying
      NIS or /etc/hosts).  To override the switch policy and query DNS
      servers directly, the server command can be used to specify a
      nameserver. This same overriding of the switch policy can also be done
      by providing a nameserver as the second argument on the command line.
      In this case, nslookup will ignore the switch policy and directly
      query nameservers, until a reset command is issued. Whenever an action
      is taken that causes the switch policy to be overridden, a warning
      message is displayed.

      Note, NIS+ is not supported by nslookup.	If the hosts source nisplus
      is found in the /etc/nsswitch.conf file. It will be ignored.

 ARGUMENTS
      Interactive mode is entered in the following cases:

	   +  No arguments are given.

	   +  The first argument is a hyphen (-).  The optional second
	      argument is a host name or Internet (IP) 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 is a
      host name or Internet address of a name server.





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 nslookup(1)							 nslookup(1)




      Options listed under the set command below can be specified one per
      line in the .nslookuprc file in the user's home directory.
      Alternatively, these options may be specified on the command line by
      prefixing them with a hyphen and they must precede other command line
      arguments.  For example, to change the default query type to host
      information, and the initial timeout to 10 seconds, type:

	   nslookup -query=hinfo -timeout=10

      The command line option -swdebug may be used to debug syntactic errors
      in the switch configuration file. This option turns on tracing during
      initialization, causing the switch module to print out a trace of the
      scan and parse actions on the "hosts" entry (see nsswitch.conf(4)) in
      the /etc/nsswitch.conf file.

    Interactive Commands
      Commands can be interrupted at any time by using the interrupt
      character.  To exit, type a Ctrl-D (EOF) or type exit.  To treat a
      built-in command as a host name, precede it with an escape character
      (\).  When using NIS or the host table, only host names and Internet
      addresses are allowed as commands.  An unrecognized command is
      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 returned.  If host is a name and
		     does not have a trailing period, one or more domains
		     are appended to the name (this behavior depends on the
		     state of the set options domain, srchlist, defname, and
		     search).  Answers from a name server's cache are
		     labeled ``non-authoritative.''

      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.  When
		     server is used while the current name service being
		     pointed to is either NIS or /etc/hosts, then the switch
		     policy will be overridden until a reset is issued.

      root	     Changes the default server to the server for the root
		     of the domain name space.	Currently, the host
		     ns.nic.ddn.mil is used (this command is a synonym for
		     lserverns.nic.ddn.mil).  The name of the root server
		     can be changed with the set root command.

      policy	     Prints out the policy read from the switch
		     configuration file. The number of name services
		     specified in the file are shown, as well as the order
		     and criteria on how the name services are to be used.



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 nslookup(1)							 nslookup(1)




		     The four statuses of the criteria are represented by
		     the four positions within the square brackets. The
		     order of the statuses are: SUCCESS, NOTFOUND, UNAVAIL
		     and TRYAGAIN. The two actions of the criteria are
		     represented by the two possible letters used in the
		     four status positions: R for return and C for continue.
		     However, if no criteria is specified between two
		     sources, then the default actions are assigned to the
		     statuses:
			  SUCCESS=	  return
			  NOTFOUND=	  continue
			  UNAVAIL=	  continue
			  TRYAGAIN=	  continue

      finger [name] [>&gt&gt> filename]
      finger [name] [>&gt&gt>>&gt&gt> 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.
		     >&gt&gt> and >&gt&gt>>&gt&gt> can be used to redirect output in the usual
		     manner.

      ls [option] domain [>&gt&gt> filename]
      ls [option] domain [>&gt&gt>>&gt&gt> 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:

			  -t querytype	 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 -t WKS).

		     When output is directed to a file, # characters are
		     printed for every 50 records received from the server.

      view filename  Sorts and lists the output of previous ls command(s)
		     using more (see more(1)).



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      help
      ?		     Prints a brief summary of commands.

      exit	     Exits the program.

      reset	     Returns to the use of the configured name service
		     switch policy and resets to use the original
		     nameservers.

      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.

			  cl[ass]=value	 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)

			  [no]deb[ug]	 Turn debugging mode on.  More
					 information is printed about the
					 packet sent to the server and the
					 resulting answer.  (Default =
					 nodebug)

			  [no]d2	 Turn exhaustive debugging mode on.
					 Essentially all fields of every
					 packet are printed.  (Default =
					 nod2)

			  [no]def[name]	 If set, append the default domain
					 name to a single-component lookup
					 request (i.e., one that does not
					 contain a period character).
					 (Default = defname)



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			  do[main]=name	 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)

			  [no]ig[nore]	 Ignore truncation errors.  (Default
					 = noignore)

			  q[uerytype]=value
			  ty[pe]=value	 Change the type of information
					 returned from a query to one of:

					      A		  Host's Internet
							  address

					      ANY	  All types of data

					      CNAME	  Canonical name for
							  an alias

					      GID	  Group ID

					      HINFO	  Host CPU and
							  operating system
							  type

					      MB	  Mailbox domain
							  name

					      MG	  Mail group member

					      MINFO	  Mailbox or mail
							  list information

					      MR	  Mail rename domain
							  name





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					      MX	  Mail exchanger

					      NS	  Name server for
							  the named zone

					      PTR	  Host name if the
							  query is an
							  Internet address,
							  otherwise the
							  pointer to other
							  information.

					      SOA	  Start of authority
							  record

					      TXT	  Text information

					      UID	  User ID

					      UINFO	  User information

					      WKS	  Well-known service
							  description

			  po[rt]=value	 Change the default TCP/UDP name
					 server port to value.	(Default =
					 53)

			  [no]rec[urse]	 Tell the name server to query other
					 servers if it does not have the
					 information.  (Default = recurse)

			  ret[ry]=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 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)

			  ro[ot]=host	 Change the name of the root server
					 to host.  This affects the root
					 command.  (Default =
					 ns.nic.ddn.mil)

			  [no]sea[rch]	 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



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 nslookup(1)							 nslookup(1)




					 list to the request until an answer
					 is received.  See hostname(5).
					 (Default = search)

			  srchl[ist]=name1/name2/...
					 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,
					 /etc/resolv.conf or LOCALDOMAIN)

			  [no]swtr[ace]	 When set, this flag causes nslookup
					 to print out information about the
					 sources used for resolving a name
					 or an address lookup. This flag
					 traces the behavior generated by
					 the switch policy.  (Default =
					 noswtrace)

			  t[imeout]=number
					 Change the initial timeout interval
					 for waiting for a reply to number
					 seconds.  Each retry doubles the
					 timeout period.  (Default = 5
					 seconds)

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





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	   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 server could not be made at the
		present time.

	   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.

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

 AUTHOR
      nslookup was developed by the University of California, Berkeley.

 FILES
      /etc/resolv.conf		    Initial domain name and name server
				    addresses
      $HOME/.nslookuprc		    User's initial options

 SEE ALSO
      named(1M), resolver(3N), resolver(4), nsswitch.conf(4), hostname(5),

      RFC1034, RFC1035















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