.\" $OpenBSD: nslookup.1,v 1.1 2020/02/07 09:58:52 florian Exp $
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.Dd $Mdocdate: February 7 2020 $
.Dt NSLOOKUP 1
.Os
.Sh NAME
.Nm nslookup
.Nd query Internet name servers interactively
.Sh SYNOPSIS
.Nm
.Op Fl option
.Op Ar name | -
.Op Ar server
.Sh DESCRIPTION
The
.Nm
command queries Internet domain name servers.
It 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.
.Pp
Interactive mode is entered in the following cases:
.Bl -enum
.It
when no arguments are given (the default name server will be used)
.It
when the first argument is a hyphen (-) and the second argument is
the host name or Internet address of a name server.
.El
.Pp
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.
.Pp
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:
.Bd -literal -offset indent
nslookup -query=hinfo -timeout=10
.Ed
.Pp
The
.Fl version
option causes
.Nm
to print the version
number and immediately exits.
.Sh INTERACTIVE COMMANDS
.Bl -tag -width Ds -compact
.It Ic exit
Exit the program.
.Pp
.It Ic host Op Ar 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 search list is used
to qualify the name.
.Pp
To look up a host not in the current domain, append a period to the name.
.Pp
.It Ic lserver Ar domain
.It Ic server Ar domain
Change the default server to
.Ar domain ;
.Ic lserver
uses the initial server to look up information about
.Cm domain ,
while
.Ic 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.
.Pp
.It Ic set Cm keyword Ns = Ns Ar value
This command is used to change state information that affects the lookups.
Some keywords may be abbreviated, as shown in parentheses.
Valid keywords are:
.Bl -tag -width Ds
.It Cm all
Prints the current values of the frequently used options to
.Ic set .
Information about the  current default server and host is also printed.
.It Cm class Ns = Ns Ar value
.Pq Cm cl
Change the query class to one of:
.Pp
.Bl -tag -width Ds -compact
.It Cm ANY
wildcard
.It Cm CH
the Chaos class
.It Cm HS
the Hesiod class
.It Cm IN
the Internet class
.El
.Pp
The class specifies the protocol group of the information.
The default is
.Cm IN .
.It Xo
.Op Cm no Ns
.Cm d2
.Xc
Turn debugging mode on or off.
This displays more about what nslookup is doing.
The default is
.Cm nod2 .
.It Xo
.Op Cm no Ns
.Cm debug
.Xc
.Pq Cm nodeb
Turn on or off the display of the full response packet and any intermediate
response packets when searching.
The default is
.Cm nodebug .
.It Cm domain Ns = Ns Ar name
Sets the search list to
.Ar name .
.It Xo
.Op Cm no Ns
.Cm fail
.Xc
Try the next name server if a name server responds with SERVFAIL or a referral
.Pq Cm nofail
or terminate query
.Pq Cm fail
on such a response.
The default is
.Cm nofail .
.It Cm ndots Ns = Ns Ar number
Set the number of dots (label separators) in a domain that will disable
searching.
Absolute names always stop searching.
.It Cm port Ns = Ns Ar value
.Pq Cm po
Change the default TCP/UDP name server port to
.Ar value .
The default is port 53.
.It Oo Cm query Oc Ns Cm type Ns = Ns Ar value
.Pq Cm q , ty
Change the type of the information query.
The default is
.Sq A .
.It Xo
.Op Cm no Ns
.Cm recurse
.Xc
.Pq Cm rec
Tell the name server to query other servers if it does not have the information.
The default is
.Cm recurse .
.It Cm retry Ns = Ns Ar number
Set the number of retries to number.
.It Xo
.Op Cm no Ns
.Cm search
.Xc
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.
The default is
.Cm search .
.It Cm timeout Ns = Ns Ar number
Change the initial timeout interval for waiting for a
reply to number seconds.
.It Xo
.Op Cm no Ns
.Cm vc
.Xc
Always use a virtual circuit when sending requests to the server.
The default is
.Cm novc .
.El
.Pp
.It Ic ?\&
not implemented
.It Ic finger
not implemented
.It Ic help
not implemented
.It Ic ls
not implemented
.It Ic root
not implemented
.It Ic view
not implemented
.El
.Sh FILES
.Pa /etc/resolv.conf
.Sh EXIT STATUS
The
.Nm
command returns with an exit status of 1 if any query failed, and 0 otherwise.
.Sh SEE ALSO
.Xr dig 1 ,
.Xr host 1
.Sh AUTHORS
.An -nosplit
.An Internet Systems Consortium, Inc .