nslookup(1) General Commands Manual nslookup(1)
nslookup - interactively query servers running BIND, or BIND and Hesiod together
/usr/ucb/nslookup [ host ][ server ]
/usr/ucb/nslookup [ - ][ server ]
The command queries the BIND/Hesiod servers. This command has two modes: interactive and non-interactive. Interactive mode allows you to
query the BIND/Hesiod server for information about various hosts and domains. Non-interactive mode allows you to obtain just the name and
Internet address of a host or domain.
Use interactive mode if you have no arguments to provide. In this case, queries the default BIND/Hesiod server. To specify a BIND/Hesiod
server to query, the first argument should be a dash (-) and the second argument should be the name of the server.
Use non-interactive mode when the name of the host you are looking up is the first argument. The optional second argument specifies a
BIND/Hesiod server. If you do not supply a second argument, the current BIND/Hesiod server is queried.
To terminate the command from within interactive mode, press <CTRL/D>. To terminate only the current lookup activity, press <CTRL/C>.
The host option is the name of the host for which you are looking up information. If you do not specify a server, the default server
is queried. You can specify the server by either name or IP address.
The - option returns the name and IP address of the default server, or the server you specify. It then places you in interactive
mode. If you do not specify a server, the default server is queried. You can specify the server by either name or IP address.
The command line length must be less than 80 characters. Any unrecognized command is interpreted as a host name. The following are the
Looks up information for host using the current default server or using server if it is specified.
Changes the default server to the server specified. This option uses the current default server.
Changes the default server to the server specified. This option uses the initial default server to look up information about the
root Changes the default server to the server for the root of the domain name space specified. Currently, the host ns.nic.ddn.mil is used.
finger [ name ] [ > [ > ] file ]
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=value command. The name field is optional; but if used, it specifies a user
name. You can use the > and >> options to redirect output to the file specified.
ls [ -adhlmst ] domain [ > [ > ] file ]
Lists the information available for the domain specified. The default output contains host names and their Internet addresses.
-a Lists aliases of hosts in the domain, CNAME entries.
-d Lists all entries in the domain.
-h Lists CPU and operating system information for the domain, HINFO entries.
-l Same as -d.
-m Lists mail exchangers in the domain, MX entries.
-s Lists well known services in the domain, WKS entries.
-t Lists Hesiod text information, TXT entries.
If you redirect the output to a file, hash marks are printed for every 50 records received from the server.
Sorts and lists the output of the command with the command.
help or ?
Print a brief summary of the commands and options.
Changes the set options that affect the lookups, except for keywords and which display information. Valid keywords are:
all Prints the current values of the options you can set, as well as information about the current default server.
ALL Prints the current values of the options you can set, as well as information about the current default server. In addition,
the ALL option prints the server state information.
[no]debug Turns on debugging mode. Verbose information is printed about the packet sent to the server and the resulting answer.
The default is nodebug , which you can abbreviate to [no]deb.
Appends the default domain name to every lookup. The default is nodefname, which you can abbreviate to [no]def.
Tells the BIND/Hesiod server to query other servers if it does not have the information. The default is recurse, and the
abbreviation is [no]rec.
[no]vc Uses a TCP connection when sending requests to the server. The default is novc, and the abbreviation is [no]v.
Changes the default domain to the domain name specified. The default domain name is appended to all lookup requests if the
defname option is set. The default value is set in the file, which you can abbreviate to do.
Changes the class of information returned from a query to one of the following values:
IN Internet (default)
The abbreviation for the class option is cl.
Changes the type of information returned from a query to value. The following is a list of the most common values:
A host Internet address (default)
CNAME canonical name for an alias
MX mail exchanger
NS name server
PTR host Internet name
SOA Start of authority
TXT A Hesiod data query
WKS A well known service
The abbreviation for the querytype option is q.
Sets the number of retries to the number specified. If 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 to be resent before
giving up. The default retry number is and the abbreviation for the retry option is ret.
root=host Changes the name of the root server to the host name specified. This affects the root command. The default is and the
abbreviation is ro.
Changes the time-out interval for waiting for a reply to the number specified (in seconds). The default is 10 seconds, and
the abbreviation for the timeout option is t.
The domain name space is tree-structured and has six top-level domains:
o ARPA (for ARPAnet hosts)
The ARPA domain is currently one of the top-level domains, but is being phased out.
o COM (for commercial establishments)
o EDU (for educational institutions)
o GOV (for government agencies)
o ORG (for not for profit organizations)
o MIL (for MILNET hosts)
If you are looking for a specific host, you need to know something about the host's organization in order to determine the top-level domain
it belongs to. For instance, if you want to find the Internet address of a host at UCLA, do the following:
1. Connect with the root server, using the command. The root server of the name space has knowledge of the top-level domains.
2. Connect with a server for the domain. The domain name for UCLA, which is a university, is To connect with this server, you can type:
> server ucla.edu
The response is the names of the hosts that act as servers for the domain Note that the root server does not have information about
but knows the names and addresses of hosts that do. All future queries are sent to the UCLA BIND server.
3. Request information about a particular host in the domain, for example, To do this, type the host name. To request a list of hosts in
the UCLA domain, use the command. The command requires a domain name (in this case, as an argument.
Note that if you are connected with a BIND server that handles more than one domain, all lookups for host names must be fully specified
with its domain. For instance, the domain is served by which also services the and domains. A lookup request for the host in the domain
must be specified as However, you can use the set domain=name and set defname commands to automatically append a domain name to each
After a successful lookup of a host, use the command to see who is on the system or to get information about a specific person. To get
other information about the host, use the set querytype=value command, which allows you to change the type of information obtained and
request another lookup. The command requires that the information requested information be of type A, a host Internet address.
If you have set up Hesiod on your ULTRIX system and would like to look at this information, you must use the and commands, where value is
HS and TXT respectively.
The following example presumes that the database is set up to be distributed with BIND/Hesiod. The answer received from the command is
that 128.45 is the network number for the network named in the networks.dec.com domain.
Default Server: localhost.dec.com
> set cl=hs
> set q=txt
If the lookup request was not successful, the command displays one of the following error messages:
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).
Depending on the query type set with the set querytype command, no information about the host was available, although the host name is
The host or domain name does not exist.
The connection to the BIND/Hesiod server was refused.
Network is unreachable
The connection to the BIND/Hesiod server cannot be made at the current time.
The BIND/Hesiod server found an internal inconsistency in its database and could not return a valid answer.
The BIND/Hesiod server refused to service the request.
The name server found that the request packet was not in the proper format. Contact your DIGITAL Field Service representative.
BIND server data file directory
BIND server boot file
BIND primary server hosts file
BIND primary server reverse address hosts file
BIND server local host reverse address host file
BIND server cache file
BIND data file
finger(1), more(1), nsquery(1), resolver(3), resolver(5), named(8)
Guide to the BIND/Hesiod Service