nslookup - query Internet name servers interactively
nslookup [-option] [name | -] [server]
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
prints 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 is
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.
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, with an initial timeout of 10 seconds, type:
nslookup -query=hinfo -timeout=10
The
-version option causes
nslookup to print the version number
and immediately exit.
- host [server]
- This command looks 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 search list is used to qualify the name.
To look up a host not in the current domain, append a period to the
name.
- server domain | lserver domain
- These commands 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 cannot be found, the names of servers that might have
the answer are returned.
- root
- This command is not implemented.
- finger
- This command is not implemented.
- ls
- This command is not implemented.
- view
- This command is not implemented.
- help
- This command is not implemented.
- ?
- This command is not implemented.
- exit
- This command exits the program.
- set keyword[=value]
- This command is used to change state information that
affects the lookups. Valid keywords are:
- all
- This keyword prints the current values of the frequently
used options to set. Information about the current default server
and host is also printed.
- class=value
- This keyword changes the query class to one of:
- IN
- the Internet class
- CH
- the Chaos class
- HS
- the Hesiod class
- ANY
- wildcard
The class specifies the protocol group of the information. The default is
IN; the abbreviation for this keyword is
cl.
- nodebug
- This keyword turns on or off the display of the full
response packet, and any intermediate response packets, when searching.
The default for this keyword is nodebug; the abbreviation for this
keyword is [no]deb.
- nod2
- This keyword turns debugging mode on or off. This displays
more about what nslookup is doing. The default is nod2.
- domain=name
- This keyword sets the search list to name.
- nosearch
- If the lookup request contains at least one period, but
does not end with a trailing period, this keyword appends the domain names
in the domain search list to the request until an answer is received. The
default is search.
- port=value
- This keyword changes the default TCP/UDP name server port
to value from its default, port 53. The abbreviation for this
keyword is po.
- querytype=value | type=value
- This keyword changes the type of the information query to
value. The defaults are A and then AAAA; the abbreviations for
these keywords are q and ty.
Please note that it is only possible to specify one query type. Only the
default behavior looks up both when an alternative is not specified.
- norecurse
- This keyword tells the name server to query other servers
if it does not have the information. The default is recurse; the
abbreviation for this keyword is [no]rec.
- ndots=number
- This keyword sets the number of dots (label separators) in
a domain that disables searching. Absolute names always stop
searching.
- retry=number
- This keyword sets the number of retries to
number.
- timeout=number
- This keyword changes the initial timeout interval to wait
for a reply to number, in seconds.
- novc
- This keyword indicates that a virtual circuit should always
be used when sending requests to the server. novc is the
default.
- nofail
- This keyword tries the next nameserver if a nameserver
responds with SERVFAIL or a referral (nofail), or terminates the query
(fail) on such a response. The default is nofail.
nslookup returns with an exit status of 1 if any query failed, and 0
otherwise.
If
nslookup has been built with IDN (internationalized domain name)
support, it can accept and display non-ASCII domain names.
nslookup
appropriately converts character encoding of a domain name before sending a
request to a DNS server or displaying a reply from the server. To turn off IDN
support, define the
IDN_DISABLE environment variable. IDN support is
disabled if the variable is set when
nslookup runs, or when the
standard output is not a tty.
/etc/resolv.conf
dig(1),
host(1),
named(8).
Internet Systems Consortium
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