Manual page for NSLOOKUP(8C)
nslookup - query domain name servers interactively
SYNOPSIS
nslookup
[
-l
] [
address
]
DESCRIPTION
nslookup
is an interactive program to query
Internet domain name servers. The user can contact servers to
request information about a specific host or print
a list of hosts in the domain.
OPTIONS
- -l
-
Use the local host's name server instead of the servers in
/etc/resolv.conf.
(If
/etc/resolv.conf
does not exist or does not contain server information, the
-l
option does not have any effect).
- address
-
Use the name server on the host machine
with the given Internet address.
USAGE
Overview
The Internet domain name-space is tree-structured, with
top-level domains such as:
-
- COM
-
commercial establishments
- EDU
-
educational institutions
- GOV
-
government agencies
- MIL
-
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 machine at
UCLA,
do the following:
- Connect with the root server using the
root
command.
The root server of the name space has knowledge of the top-level
domains.
- Since
UCLA
is a university, its domain name is
ucla.edu.
Connect with a server for the
ucla.edu
domain with the command
serverucla.edu.
The response will print
the names of hosts that act as servers for that domain.
Note: the root server does not have information about
ucla.edu,
but knows the names and addresses of hosts that do.
Once located by the root server,
all future queries will be sent to the
UCLA
name server.
- To request information about a particular host in the domain
(for instance,
locus),
just type the host name.
To request a listing of hosts in the
UCLA
domain, use the
ls
command.
The
ls
command requires a domain name (in this case,
ucla.edu)
as an argument.
Note: if you are connected with a name server that handles
more than one domain, all lookups for
host names must be fully specified with its domain.
For instance, the domain
harvard.edu
is served by
seismo.css.gov,
which also services the
css.gov
and
cornell.edu
domains. A lookup request for the host
aiken
in the
harvard.edu
domain must be specified as
aiken.harvard.edu.
However, the
set domain=name
and
set defname
commands can be used to automatically
append a domain name to each request.
After a successful lookup of a host, use the
finger
command to
see who is on the system, or to finger a specific person.
To get other information about the host, use the
set querytype=value
command to change the type of information desired and request another
lookup.
(finger
requires the type to be A.)
Commands
Commands may be interrupted at any time by typing
CTRL-C.
To exit, type
CTRL-D
(EOF).
The command line length must be less than 80 characters.
Note: 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 current 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
sri-nic.arpa
is used; this command is a synonym for
`lserver sri-nic.arpa'.)
The name of the root server can be changed with the
set root
command.
- finger [ name]
-
Connect with the finger server on the current host, which
is defined by a previous successful lookup for a host's
address information (see the
set querytype=A
command).
As with the shell, output can be redirected to a named file
using
>
and
>>.
- "ls [-ah]
-
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.
As with the shell, output can be redirected to a named file
using
>
and
>>.
When output is directed to a file, hash marks are printed for every
50 records received from the server.
- viewfilename
-
Sort and list the output of the
ls
command with
more.1
- help
-
- ?
-
Print a brief summary of commands.
- setkeyword
[
= 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]deb[ug]
-
Turn debugging mode on. A lot more information is printed about the
packet sent to the server and the resulting answer.
The default is
nodebug.
- [no]def[name]
-
Append the default domain name to every lookup.
The default is
nodefname.
- do[main]=filename
-
Change the default domain name to
filename.
The default domain name is appended to all lookup requests if
defname
option has been set.
The default is the value in
/etc/resolv.conf.
- q[querytype]=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.
- MB
-
The mailbox domain name.
- MG
-
The mail group member.
- MINFO
-
The mailbox or mail list information.
(Other types specified in the
RFC883
document are valid, but are not
very useful.)
- [no]recurse
-
Tell the name server to query other servers if it does not have the
information.
The default is
recurse.
- ret[ry]=count
-
Set the number of times to retry a request before giving up to
count.
When a reply to a request is not received within a certain
amount of time (changed with
set timeout),
the request is resent. The default is
count
is
2.
- ro[ot]=host
-
Change the name of the root server to
host.
This
affects the
root
command. The default root server is
sri-nic.arpa.
- t[timeout]=interval
-
Change the time-out for a reply to
interval
seconds.
The default
interval is
10
seconds.
- [no]v[c]
-
Always use a virtual circuit when sending requests to the server.
The default is
novc.
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
resolv.conf.5
named.8c
RFC 1034,
RFC 1035
[a manual with the abbreviation ADMIN]
Created by unroff & hp-tools.
© somebody (See intro for details). All Rights Reserved.
Last modified 11/5/97