nslookup(1)nslookup(1)Namenslookup - interactively query servers running BIND, or BIND and Hesiod
together
Syntax
/usr/ucb/nslookup [ host ][ server ]
/usr/ucb/nslookup [ - ][ server ]
Description
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 cur‐
rent 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>.
Non-interactive Options
host [server]
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.
- [server]
The - option returns the name and IP address of the default
server, or the server you specify. It then places you in interac‐
tive mode. If you do not specify a server, the default server is
queried. You can specify the server by either name or IP address.
Interactive Options
The command line length must be less than 80 characters. Any unrecog‐
nized command is interpreted as a host name. The following are the
standard options:
host [server]
Looks up information for host using the current default server or
using server if it is specified.
server server
Changes the default server to the server specified. This option
uses the current default server.
lserver server
Changes the default server to the server specified. This option
uses the initial default server to look up information about the
server specified.
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.
view file
Sorts and lists the output of the command with the command.
help or ?
Print a brief summary of the commands and options.
set keyword[=value]
Changes the set options that affect the lookups, except for key‐
words 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.
[no]defname
Appends the default domain name to every lookup. The
default is nodefname, which you can abbreviate to
[no]def.
[no]recurse
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.
domain=name
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.
class=value
Changes the class of information returned from a query
to one of the following values:
IN Internet (default)
HS Hesiod
ANY any
The abbreviation for the class option is cl.
querytype=value
Changes the type of information returned from a query to
value. The following is a list of the most common val‐
ues:
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.
retry=number
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.
timeout=number
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.
Tutorial
The domain name space is tree-structured and has six top-level domains:
· ARPA (for ARPAnet hosts)
The ARPA domain is currently one of the top-level domains, but is
being phased out.
· COM (for commercial establishments)
· EDU (for educational institutions)
· GOV (for government agencies)
· ORG (for not for profit organizations)
· 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:
# nslookup
> 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 ser‐
vices 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 request.
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.
Hesiod Tutorial
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 dis‐
tributed with BIND/Hesiod. The answer received from the command is
that 128.45 is the network number for the network named in the net‐
works.dec.com domain.
# nslookup
Default Server: localhost.dec.com
Address: 127.0.0.1
> set cl=hs
> set q=txt
> ethernet.networks
Server: localhost.dec.com
Address: 127.0.0.1
ethernet.networks.dec.com ethernet:128.45
>
Diagnostics
If the lookup request was not successful, the command displays one of
the following error messages:
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, although the host name is
valid.
Non-existent domain
The host or domain name does not exist.
Connection refused
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.
Server failure
The BIND/Hesiod server found an internal inconsistency in its database
and could not return a valid answer.
Refused
The BIND/Hesiod server refused to service the request.
Format error
The name server found that the request packet was not in the proper
format. Contact your DIGITAL Field Service representative.
Files
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
See Alsofinger(1), more(1), nsquery(1), resolver(3), resolver(5), named(8)
Guide to the BIND/Hesiod Service
nslookup(1)