Visit Our UNIX and Linux User Community

Linux and UNIX Man Pages

Test Your Knowledge in Computers #224
Difficulty: Easy
True or False?
Linux & Unix Commands - Search Man Pages

nslookup(1) [bsd man page]

NSLOOKUP(1)						      General Commands Manual						       NSLOOKUP(1)

nslookup - query name servers interactively SYNOPSIS
nslookup [ host-to-find | - [ server address | server name ]] 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 various 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. ARGUMENTS
Interactive mode is entered in the following cases: a) when no arguments are given (the default name server will be used), and b) when the first argument is a hyphen (-) and the second argument is the host name 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 speci- fies a name server. INTERACTIVE COMMANDS
Commands may be interrupted at any time by typing a control-C. To exit, type a control-D (EOF). The command line length must be less than 80 characters. N.B. 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 cur- rent 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 is used. (This command is a synonym for the lserver 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. 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, hash marks are printed for every 50 records received from the server. view filename Sorts and lists the output of previous ls command(s) with more(1). help ? Prints a brief summary of commands. 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. [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, abbreviation = do) 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 RFC883 document are valid but aren't 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 =, 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 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 program. 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), resolver(5), named(8), RFC882, RFC883 AUTHOR
Andrew Cherenson 4.3 Berkeley Distribution November 21, 1987 NSLOOKUP(1)

Featured Tech Videos