nslookup [-option ...] [host-to-find | -[server]]
Nslookup is a program to query Internet domain name servers. Nslookup has two modes: interactive and non-interactive. 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. Non-interactive mode is used to print just the name and requested information for a host or do main.
Interactive mode is entered in the following cases: a) when no arguments are given (the default name server will be used), b) when the first argument is a hyphen (-) and the second argument is the host name or Internet address of a name server. Non-interactive mode is used 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 host name or address of a name server. The options listed under the ``set'' command below 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 pre cede the arguments and are prefixed with a hyphen. For example, to change the default query type to host information, and the initial time out to 10 seconds, type: nslookup -query=hinfo -timeout=10
Commands may be interrupted at any time by typing a control-C. To exit, type a control-D (EOF) or type exit. The command line length must be less than 256 characters. To treat a built-in command as a host name, precede it with an escape character (.& .) N.B.: unrecognized command will be interpreted as a N.B.:0 0N.B.:1 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, the de fault domain name is appended to the name. (This behavior de pends on the state of the set options domain, srchlist, defname, and search.) To look up a host not in the current domain, append a period to the name. server domain lserver domain finger [name] [> filename] finger [name] [>> filename] Connects with the finger server on the current host. The cur rent host is defined when a previous lookup for a host was suc cessful and returned address information (see the ``set querytype=A'' command). The name is optional. > and >> can be used to redirect output in the usual manner. ls [option] domain [> filename] ls [option] domain [>> 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 follow ing: -t querytype lists all records of the specified type (see querytype be low). -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, 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. exit Exits the program. 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 frequently-used op tions to set. Information about the current default server and host is also printed. The class specifies the protocol group of the informa tion. (Default = IN; abbreviation = cl) [no] debug Turn debugging mode on. A lot more information is printed about the packet sent to the server and the re sulting answer. (Default = nodebug; abbreviation = [no]deb) [no] d2 Turn exhaustive debugging mode on. Essentially all fields of every packet are printed. (Default = nod2) domain=name Change the default domain name to name. The default do main name is appended to a lookup request depending on the state of the defname and search options. The do main 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(1), /etc/resolv.conf, or LOCALDOMAIN; abbreviation = do) srchlist=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 exam ple, 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'' com mand. Use the ``set all'' command to display the list. (Default = value based on hostname(1), /etc/resolv.conf, or LOCALDOMAIN; abbreviation = srchl) [no] defname If set, append the default domain name to a single-com ponent lookup request (i.e., one that does not contain a period). (Default = defname; abbreviation = [no]defname) (Default = 53; abbreviation = po) querytype=value type=value Change the type of information query to one of: A the host's Internet 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. NS the name server for the named zone. PTR the host name if the query is an Internet ad dress; otherwise, the pointer to other infor mation. SOA the domain's ``start-of-authority'' informa tion. 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 RFC-1035 document. (Default = A; abbreviations = q, ty) [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 timeout period is doubled and the request is resent. The retry value controls how many times a request is resent before giv ing up. (Default = 4, abbreviation = ret) root=host (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; abbreviation = [no]ig)
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 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 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 prop er format. It may indicate an error in nslookup.
/etc/resolv.conf initial domain name and name server ad dresses $HOME/.nslookuprc user's initial options Specification''.
Andrew Cherenson 4th Berkeley Distribution June 24, 1990 6
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