nslookup(TC) nslookup(TC) Name nslookup - query name servers interactively Syntax 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 vari- ous 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. Options Interactive mode is entered in the following cases: + when no arguments are given (the default name server will be used), and + 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 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 informa- tion, and the default timeout to 10 seconds, type: nslookup -query=hinfo -timeout=10 Interactive commands Commands may be interrupted at any time by typing the system interrupt character (<Del> by default). To exit, type a <Ctrl>D (EOF). The com- mand line length must be less than 80 characters. Note that an unrecog- nized 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 not 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.nic.ddn.mil'' is used. (This command is a synonym for the lserver ns.nic.ddn.mil.) 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] 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, 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(C). help ? Prints a brief summary of commands. exit Exits the program. set keyword[=value] This command changes state information that affects the look- ups. 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. class=name Set query class to one of IN (Internet), CHAOS, HESIOD or ANY. (Default = IN) [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, abbrevi- ation = do) [no]ignore Ignore truncate error. (Default = noignore) port=port# Connect to name server using port#. (Default = well known port number) srchlist=domain Set search list to domain. 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 RFC1035 document are valid but are not 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 = ns.nic.ddn.mil, 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 com- monly 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 /usr/lib/nslookup.hlp /etc/resolv.conf initial domain name and name server addresses /usr/lib/nslookup.hlp summary of commands See also resolver(SLIB), resolver(SFF), named(ADMN) RFC-1034 ``Domain Names -- Concepts and Facilities'' RFC-1035 ``Domain Names -- Implementation and Specification''