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nslookup(8)							  nslookup(8)



NAME

  nslookup - Queries Internet name servers interactively

SYNOPSIS

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

DESCRIPTION

  The nslookup command is a program that is used to query Internet domain
  name servers.	 The nslookup command has two modes: interactive and nonin-
  teractive.

  Noninteractive mode
      Noninteractive mode is used to print just	the name and requested infor-
      mation for a host	or domain.  Noninteractive mode	is invoked 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 hostname or
      address of a name	server.

  Interactive mode
      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.  Interactive mode	is invoked when	you specify nslookup without
      arguments	(the default name server will be used),	or when	the first
      argument you specify is a	- (dash) and the second	argument is the	host-
      name or Internet address of a name server.

  The options listed under the set command 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 - (dash).  For example, to change the
  default query	type to	host information, and the initial time-out to 10
  seconds, enter:

       nslookup	-query=hinfo  -timeout=10

  Interactive Commands


  Commands may be interrupted at any time by entering <&lt;Ctrl-c>&gt;.	To exit,
  enter	<&lt;Ctrl-d>&gt; (EOF) or type exit. The command line length must be less
  than 256 characters.	To treat a built-in command as a hostname, precede it
  with an escape character \ (backslash). Note that an unrecognized command
  will be interpreted as a hostname.

  host [server]
      Looks 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 . (dot) to the name.

  server domain

  lserver domain
      Changes 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 cannot	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 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 command.

  finger [name]	[>&gt; filename]

  finger [name]	[>&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. The>&gt;	and >&gt;>&gt; (redirection symbols) can be used to redirect
      output in	the usual manner.

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

  ls [option] domain [>&gt;>&gt; filename]
      Lists the	information available for domain, optionally creating or
      appending	to filename. The default output	contains hostnames and their
      Internet addresses.  option can be one of	the following:

      -t querytype
	  Lists	all records of the specified type (see querytype later in
	  this reference page).

      -a  Lists	aliases	of hosts in the	domain.	 This option is	a synonym for
	  -t CNAME.

      -d  Lists	all records for	the domain.  This option is a synonym for -t
	  ANY.

      -h  Lists	CPU and	operating system information for the domain. This
	  option is a synonym for -t HINFO.

      -s  Lists	well-known services of hosts in	the domain. This option	is a
	  synonym for -t WKS.  When output is directed to a file, # (number
	  signs) are printed for every 50 records received from	the server.

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

  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	look-
      ups. 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.

      class=value
	      Changes 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	pro-
		  tocol	group of the information. (Default = IN, abbreviation
		  = cl)

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

      domain=name
	      Changes 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 com-
	      ponents 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 dif-
	      ferent list. Use the set all command to display the list.
	      (Default = value from hostname, /etc/resolv.conf or LOCAL-
	      DOMAIN, abbreviation = do)

      srchlist=name1/name2/...
	      Changes the default domain name to name1 and the domain search
	      list to name1, name2, and	so on. 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, abbreviation = srchl)

      [no]defname
	      If set, appends the default domain name to a single-component
	      lookup request (that is, one that	does not contain a dot).
	      (Default = defname, abbreviation = [no]def)

      [no]search
	      If the lookup request contains at	least one . (dot) but does
	      not end with a trailing dot, appends the domain names in the
	      domain search list to the	request	until an answer	is received.
	      (Default = search, abbreviation =	[no]sea)

      port=value
	      Changes the default TCP/UDP name server port to value.
	      (Default = 53, abbreviation = po)

      querytype=value

      type=value
	      Changes the type of information query to one of:

	      A	  The host's IPv4 address.

	      AAAA
		  The host's IPv6 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.

	      NAPTR
		  The Naming AUthority PoinTeR that contains rules for map-
		  ping parts of	Uniform	Resource Identifiers (URIs) to domain
		  names.

	      NS  The name server for the named	zone.

	      PTR The hostname if the query is an Internet address; otherwise
		  the pointer to other information.

	      SOA The domain's start-of-authority information.

	      SRV The host that	can provide a specific resolution service.

	      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 RFC1035 document.
		  (Default = A,	abbreviations =	q, ty)

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

      retry=number
	      Sets the number of retries to number. When a reply to a request
	      is not received within a certain amount of time (changed with
	      set time-out), 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, abbreviation = ret)

      root=host
	      Changes the name of the root server to host.  This affects the
	      root command. (Default = ns.internic.net., abbreviation =	ro)

      timeout=number
	      Changes the initial timeout interval for waiting for a reply to
	      number seconds. Each retry doubles the timeout period. (Default
	      =	5 seconds, abbreviation	= ti)

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

      [no]ignoretc
	      Ignore packet truncation errors. (Default	= noignoretc, abbre-
	      viation =	[no]ig)




EXIT STATUS

  In noninteractive mode, nslookup can return the following values:

  0   A	match was found.

  1   No match was found, or an	error occurred.

ERRORS

  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 hostname is valid.	The query type is specified
      with the set querytype command.

  Nonexistent 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 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.

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

FILES

  /usr/bin/nslookup
      Specifies	the command path

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

  $HOME/.nslookuprc
      User's initial options

  /usr/share/misc/nslookup.help
      Summary of commands







SEE ALSO

  Commands: named(8)

  Functions: resolver(4)

  Files: resolv.conf(4)

  Specifications:  RFC1034, RFC1035