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 -query=hinfo -timeout=10
INTERACTIVE COMMANDS
Commands may be interrupted at any time by typing a control-C.
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.
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).
The
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
''
-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) with
more(1).
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 =
Op Ic 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 =
Op Ic 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 =
Op Ic 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 =
Op Ic 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 =
Op Ic no
v
[no
]
ignoretc
Ignore packet truncation errors.
(Default =
noignoretc ;
abbreviation =
Op Ic no
ig
DIAGNOSTICS
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
''
response from server
No name server is running on the server machine.
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/share/misc/nslookup.help
summary of commands
ENVIRONMENT
HOSTALIASES
file containing host aliases
LOCALDOMAIN
overrides default domain
SEE ALSO
named(8),
resolver(3),
resolver(5);
RFC-1034,
``Domain Names - Concepts and Facilities''
RFC-1035,
``Domain Names - Implementation and Specification''
