nslookup(1M) TCP/IP R4.11 nslookup(1M)
NAME
nslookup - query Internet name servers interactively
SYNOPSIS
nslookup [ -option ... ] [ host-to-find | - [ server ]]
DESCRIPTION
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 domain.
ARGUMENTS
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 -querytype=hinfo -timeout=10
INTERACTIVE COMMANDS
Commands may be interrupted at any time by typing the INTR character
(e.g., control-C). To exit, type the EOF character (e.g., control-D)
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 (\).
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 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.
root Changes the default server to the server for the root of the
domain name space. Currently, the host ns.internic.net is
used. (This command is a synonym for lserver
ns.internic.net.) The name of the root server can be changed
with the set root command.
finger [name] [> filename]
finger [name] [>> filename]
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=A command). 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
following:
-t querytype
lists all records of the specified type (see querytype
below).
-a lists aliases of hosts in the domain. Synonym for -t
CNAME.
-d lists all records for the domain. Synonym for -t ANY.
Note that some servers may limit or disable zone transfers
resulting in a 'network unreachable' message.
-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) using the
viewer specified by the PAGER shell variable (or the more
command if PAGER is unspecified).
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
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, /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, /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]def)
[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)
[no]ignoretc
Ignore packet truncation errors.
(Default = noignoretc, abbreviation = [no]ig)
DIAGNOSTICS
If the lookup request was not successful, an error message is
printed. Possible errors include:
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.
FILES
/etc/resolv.conf initial domain name and name server
addresses.
$HOME/.nslookuprc user's initial options.
/usr/lib/nslookup.help summary of commands.
ENVIRONMENT
HOSTALIASES file containing host aliases.
LOCALDOMAIN overrides default domain.
SEE ALSO
resolver(3C), resolv.conf(4M), named(1M),
RFC-1034 ``Domain Names - Concepts and Facilities''
RFC-1035 ``Domain Names - Implementation and Specification''
AUTHOR
Andrew Cherenson
Licensed material--property of copyright holder(s)