nslookup.1 (2010 09)

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nslookup(1) nslookup(1)

(BIND 9.3)

NAME

nslookup - query name servers interactively

SYNOPSIS

Single Host Mode

nslookup [-swdebug][-setoption]... host [server ]

Interactive Mode

nslookup [-swdebug][-setoption]... [

- [server ]]

DESCRIPTION

The

nslookup program queries Internet domain name servers. It follows the conﬁgured name resolu-

tion algorithm of the host and queries NIS, DNS, and host tables.

In Single Host Mode (noninteractive),

nslookup queries a name server for information about one host

or domain. This mode occurs when you specify a host in the command.

In Interactive Mode,

nslookup lets you make several requests in the same session. For example, you

can query a name server for information about various hosts and domains or print a list of hosts in the

domain. This mode occurs when you omit the host (and server ) in the command or when you use the spe-

cial

- placeholder.

Options

-setoption

Set the setoption , as deﬁned for the set command. See The set Command subsection in the

INTERACTIVE COMMANDS section.

-swdebug

Turn on tracing during command initialization, causing the switch module to print out a trace

of the scan and parse actions on the hosts database entry in the /etc/nsswitch.conf

ﬁle (see nsswitch.conf(4)). It may be used to debug syntactic errors in the switch conﬁguration

ﬁle. See also the

set option [no]trace.

Note:

swdebug is not a set command option, so you cannot turn it off in interactive mode.

Operands

host The host name or IP address of a host system. If host is present, the command is executed

immediately (noninteractively). If it is omitted,

nslookup enters interactive mode.

- Set interactive mode. This placeholder is needed if you specify server for interactive mode.

server The host name or IP address of a domain name server. If omitted,

nslookup uses the policy

described in the Default Lookup Policy subsection.

Initialization File

The setoption s and

swdebug (see the Options subsection) can be speciﬁed in a .nslookuprc startup

ﬁle in the user’s home directory. Enter them one per line without the leading hyphen (-).

Default Lookup Policy

If a server has not been speciﬁed explicitly to override the switch policy,

nslookup initializes each of the

name services in the hosts database in the switch conﬁguration ﬁle /etc/nsswitch.conf (see

nsswitch.conf(4)), but uses the ﬁrst name service for lookup. The initialization of the name services may

cause a delay in obtaining the response if any of the name services is not responding. For example, con-

sider when the

hosts database is deﬁned with the following name services:

hosts : files dns nis

If the name servers mentioned in /etc/resolv.conf (see resolver (4)) are unavailable, there will be a

delay in trying to initialize the name servers. The handling of the query thereafter follows the switch pol-

icy, as would be expected.

nslookup contacts the name servers mentioned in /etc/resolv.conf sequentially but does not

cycle through them like the resolver routines do (see resolver (3N)).

Note:

nslookup should not be used as a command-line substitute for the resolver routines unless the

differences in resolution behavior between nslookup and the resolver routines are understood and are

acceptable for the scripting environment where nslookup will be employed.

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (6 pages)

PAGE 1
nslookup(1) nslookup(1) (BIND 9.3) NAME nslookup - query name servers interactively SYNOPSIS Single Host Mode nslookup [-swdebug] [-setoption ]... host [server ] Interactive Mode nslookup [-swdebug] [-setoption ]... [- [server ] ] DESCRIPTION The nslookup program queries Internet domain name servers. It follows the configured name resolution algorithm of the host and queries NIS, DNS, and host tables.
PAGE 2
nslookup(1) nslookup(1) (BIND 9.3) The following hosts name services are recognized: dns Use the servers defined in the /etc/resolv.conf file. files Use the entries in the /etc/hosts file. nis Use the maps at the NIS server. Note: NIS+ is not supported by nslookup. If the nisplus name service is included in the hosts database, it is ignored. there is no hosts database in the /etc/nsswitch.conf file or there /etc/nsswitch.conf file, nslookup uses this name service sequence: dns nis files.
PAGE 3
nslookup(1) nslookup(1) (BIND 9.3) The output can create/overwrite (>) or append to (>>) filename . When output is directed to a file, a # character is printed to standard output for every 50 records received from the server. lserver domain See the server command. policy Print out the policy read from the hosts database in the switch configuration file (see nsswitch.conf (4)).
PAGE 4
nslookup(1) nslookup(1) (BIND 9.3) IN The Internet class. CHAOS The Chaosnet class. HESIOD The MIT Athena Hesiod class. ANY Wildcard (any of the above). The class specifies the protocol group of the information. The default is class=IN. [no]d2 Turn on [turn off] exhaustive debugging mode. Essentially all fields of every packet are printed. The default is nod2. [no]deb[ug] Turn on [turn off] debugging mode. More information is printed about the packet sent to the server and the resulting answer.
PAGE 5
nslookup(1) nslookup(1) (BIND 9.3) ret[ry]=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 the set timeout command ), the timeout period is doubled and the request is resent. The retry value controls how many times a request is resent before giving up. The default is retry=4. ro[ot]=host Change the name of the root server to host . This affects the root command. The default is root=ns.nic.ddn.mil.
PAGE 6
nslookup(1) nslookup(1) (BIND 9.3) EXAMPLES To change the default query type to host information and the initial timeout to 10 seconds, and enter interactive mode: nslookup -query=hinfo -timeout=10 AUTHOR nslookup was developed by the Internet Systems Consortium (ISC). FILES $HOME/.nslookuprc User’s initial options. /etc/hosts Host name data base. /etc/nsswitch.conf Configuration file for the name-service switch. /etc/resolv.conf Initial domain name and name server addresses.