nslookup - query Internet name servers interactively
nslookup [-option ...] [host-to-find | -[server]]
Nslookup is a program to query Internet domain name servers. 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 domain.
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 precede
the arguments and are prefixed with a hyphen. For example, to
change the default query type to host information, and the
initial timeout
to 10 seconds, type:
nslookup -query=hinfo -timeout=10
Commands may be interrupted at any time by typing a controlC. 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.: 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 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 default
domain name is appended to the name. (This
behavior depends
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
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.
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 options
to set. Information about the current default
server and host is also printed.
class=value
Change the query class to one of:
IN the Internet class
CHAOS the Chaos class
HESIOD the MIT Athena Hesiod class
ANY wildcard (any of the above)
The class specifies the protocol group of
the information.
(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 resulting
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
domain name is appended to a lookup request depending
on the state of the defname and search options. The
domain 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 example,
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'' command.
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-component
lookup request (i.e., one that does
not contain
a period).
(Default = defname; abbreviation =
[no]defname)
[no]search
If the lookup request contains at least
one period but
doesn't end with a trailing period, append
the domain
names in the domain search list to the request until an
answer is received.
(Default = search; abbreviation = [no]sea)
port=value
Change the default TCP/UDP name server
port to value.
(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 address;
otherwise, the pointer to
other information.
SOA the domain's ``start-of-authority'' information.
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 giving
up.
(Default = 4, abbreviation = ret)
root=host
Change the name of the root server to
host. This affects
the ``root'' command.
(Default = ns.internic.net.; abbreviation
= ro)
timeout=number
Change the initial timeout interval for
waiting for a
reply to number seconds. Each retry doubles the timeout
period.
(Default = 5 seconds; abbreviation = ti)
[no]vc Always use a virtual circuit when sending
requests to
the server.
(Default = novc; abbreviation = [no]v)
/etc/resolv.conf initial domain name and name server addresses
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 proper
format. It may indicate an error in nslookup.
dig(1), resolver(3), resolver(5), named(8)
RFC 1034 Domain Names - Concepts and Facilities
RFC 1035 Domain Names - Implementation and Specification
Andrew Cherenson
OpenBSD 3.6 June 24, 1990
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