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.\" Man page generated from reStructuredText.
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.TH "NSUPDATE" "1" "@RELEASE_DATE@" "@PACKAGE_VERSION@" "BIND 9"
.SH NAME
nsupdate \- dynamic DNS update utility
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.SH SYNOPSIS
.sp
\fBnsupdate\fP [\fB\-d\fP] [\fB\-D\fP] [\fB\-i\fP] [\fB\-L\fP level] [ [\fB\-g\fP] | [\fB\-o\fP] | [\fB\-l\fP] | [\fB\-y\fP [hmac:]keyname:secret] | [\fB\-k\fP keyfile] ] [\fB\-t\fP timeout] [\fB\-u\fP udptimeout] [\fB\-r\fP udpretries] [\fB\-v\fP] [\fB\-T\fP] [\fB\-P\fP] [\fB\-V\fP] [ [\fB\-4\fP] | [\fB\-6\fP] ] [filename]
.SH DESCRIPTION
.sp
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\fBnsupdate\fP is used to submit Dynamic DNS Update requests, as defined in
\fI\%RFC 2136\fP, to a name server. This allows resource records to be added or
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removed from a zone without manually editing the zone file. A single
update request can contain requests to add or remove more than one
resource record.
.sp
Zones that are under dynamic control via \fBnsupdate\fP or a DHCP server
should not be edited by hand. Manual edits could conflict with dynamic
updates and cause data to be lost.
.sp
The resource records that are dynamically added or removed with
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\fBnsupdate\fP must be in the same zone. Requests are sent to the
zone\(aqs primary server, which is identified by the MNAME field of the
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zone\(aqs SOA record.
.sp
Transaction signatures can be used to authenticate the Dynamic DNS
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updates. These use the TSIG resource record type described in \fI\%RFC 2845\fP,
the SIG(0) record described in \fI\%RFC 2535\fP and \fI\%RFC 2931\fP, or GSS\-TSIG as
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described in \fI\%RFC 3645\fP\&.
.sp
TSIG relies on a shared secret that should only be known to \fBnsupdate\fP
and the name server. For instance, suitable \fBkey\fP and \fBserver\fP
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statements are added to \fB/etc/named.conf\fP so that the name server
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can associate the appropriate secret key and algorithm with the IP
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address of the client application that is using TSIG
authentication. \fBddns\-confgen\fP can generate suitable
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configuration fragments. \fBnsupdate\fP uses the \fB\-y\fP or \fB\-k\fP options
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to provide the TSIG shared secret; these options are mutually exclusive.
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.sp
SIG(0) uses public key cryptography. To use a SIG(0) key, the public key
must be stored in a KEY record in a zone served by the name server.
.sp
GSS\-TSIG uses Kerberos credentials. Standard GSS\-TSIG mode is switched
on with the \fB\-g\fP flag. A non\-standards\-compliant variant of GSS\-TSIG
used by Windows 2000 can be switched on with the \fB\-o\fP flag.
.SH OPTIONS
.INDENT 0.0
.TP
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.B \fB\-4\fP
This option sets use of IPv4 only.
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.TP
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.B \fB\-6\fP
This option sets use of IPv6 only.
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.TP
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.B \fB\-d\fP
This option sets debug mode, which provides tracing information about the update
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requests that are made and the replies received from the name server.
.TP
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.B \fB\-D\fP
This option sets extra debug mode.
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.TP
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.B \fB\-i\fP
This option forces interactive mode, even when standard input is not a terminal.
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.TP
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.B \fB\-k keyfile\fP
This option indicates the file containing the TSIG authentication key. Keyfiles may be in
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two formats: a single file containing a \fBnamed.conf\fP\-format \fBkey\fP
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statement, which may be generated automatically by \fBddns\-confgen\fP;
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or a pair of files whose names are of the format
\fBK{name}.+157.+{random}.key\fP and
\fBK{name}.+157.+{random}.private\fP, which can be generated by
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\fBdnssec\-keygen\fP\&. The \fB\-k\fP option can also be used to specify a SIG(0)
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key used to authenticate Dynamic DNS update requests. In this case,
the key specified is not an HMAC\-MD5 key.
.TP
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.B \fB\-l\fP
This option sets local\-host only mode, which sets the server address to localhost
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(disabling the \fBserver\fP so that the server address cannot be
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overridden). Connections to the local server use a TSIG key
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found in \fB/var/run/named/session.key\fP, which is automatically
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generated by \fBnamed\fP if any local \fBprimary\fP zone has set
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\fBupdate\-policy\fP to \fBlocal\fP\&. The location of this key file can be
overridden with the \fB\-k\fP option.
.TP
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.B \fB\-L level\fP
This option sets the logging debug level. If zero, logging is disabled.
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.TP
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.B \fB\-p port\fP
This option sets the port to use for connections to a name server. The default is
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53.
.TP
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.B \fB\-P\fP
This option prints the list of private BIND\-specific resource record types whose
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format is understood by \fBnsupdate\fP\&. See also the \fB\-T\fP option.
.TP
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.B \fB\-r udpretries\fP
This option sets the number of UDP retries. The default is 3. If zero, only one update
request is made.
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.TP
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.B \fB\-t timeout\fP
This option sets the maximum time an update request can take before it is aborted. The
default is 300 seconds. If zero, the timeout is disabled.
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.TP
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.B \fB\-T\fP
This option prints the list of IANA standard resource record types whose format is
understood by \fBnsupdate\fP\&. \fBnsupdate\fP exits after the lists
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are printed. The \fB\-T\fP option can be combined with the \fB\-P\fP
option.
.sp
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Other types can be entered using \fBTYPEXXXXX\fP where \fBXXXXX\fP is the
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decimal value of the type with no leading zeros. The rdata, if
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present, is parsed using the UNKNOWN rdata format, (<backslash>
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<hash> <space> <length> <space> <hexstring>).
.TP
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.B \fB\-u udptimeout\fP
This option sets the UDP retry interval. The default is 3 seconds. If zero, the
interval is computed from the timeout interval and number of UDP
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retries.
.TP
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.B \fB\-v\fP
This option specifies that TCP should be used even for small update requests. By default, \fBnsupdate\fP uses
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UDP to send update requests to the name server unless they are too
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large to fit in a UDP request, in which case TCP is used. TCP may
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be preferable when a batch of update requests is made.
.TP
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.B \fB\-V\fP
This option prints the version number and exits.
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.TP
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.B \fB\-y [hmac:]keyname:secret\fP
This option sets the literal TSIG authentication key. \fBkeyname\fP is the name of the key,
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and \fBsecret\fP is the base64 encoded shared secret. \fBhmac\fP is the
name of the key algorithm; valid choices are \fBhmac\-md5\fP,
\fBhmac\-sha1\fP, \fBhmac\-sha224\fP, \fBhmac\-sha256\fP, \fBhmac\-sha384\fP, or
\fBhmac\-sha512\fP\&. If \fBhmac\fP is not specified, the default is
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\fBhmac\-md5\fP, or if MD5 was disabled, \fBhmac\-sha256\fP\&.
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.sp
NOTE: Use of the \fB\-y\fP option is discouraged because the shared
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secret is supplied as a command\-line argument in clear text. This may
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be visible in the output from ps1 or in a history file maintained by
the user\(aqs shell.
.UNINDENT
.SH INPUT FORMAT
.sp
\fBnsupdate\fP reads input from \fBfilename\fP or standard input. Each
command is supplied on exactly one line of input. Some commands are for
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administrative purposes; others are either update instructions or
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prerequisite checks on the contents of the zone. These checks set
conditions that some name or set of resource records (RRset) either
exists or is absent from the zone. These conditions must be met if the
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entire update request is to succeed. Updates are rejected if the
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tests for the prerequisite conditions fail.
.sp
Every update request consists of zero or more prerequisites and zero or
more updates. This allows a suitably authenticated update request to
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proceed if some specified resource records are either present or missing from
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the zone. A blank input line (or the \fBsend\fP command) causes the
accumulated commands to be sent as one Dynamic DNS update request to the
name server.
.sp
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The command formats and their meanings are as follows:
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.INDENT 0.0
.TP
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.B \fBserver servername port\fP
This command sends all dynamic update requests to the name server \fBservername\fP\&.
When no server statement is provided, \fBnsupdate\fP sends updates
to the primary server of the correct zone. The MNAME field of that
zone\(aqs SOA record identify the primary server for that zone.
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\fBport\fP is the port number on \fBservername\fP where the dynamic
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update requests are sent. If no port number is specified, the default
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DNS port number of 53 is used.
.TP
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.B \fBlocal address port\fP
This command sends all dynamic update requests using the local \fBaddress\fP\&. When
no local statement is provided, \fBnsupdate\fP sends updates using
an address and port chosen by the system. \fBport\fP can also
be used to force requests to come from a specific port. If no port number
is specified, the system assigns one.
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.TP
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.B \fBzone zonename\fP
This command specifies that all updates are to be made to the zone \fBzonename\fP\&.
If no \fBzone\fP statement is provided, \fBnsupdate\fP attempts to
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determine the correct zone to update based on the rest of the input.
.TP
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.B \fBclass classname\fP
This command specifies the default class. If no \fBclass\fP is specified, the default
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class is \fBIN\fP\&.
.TP
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.B \fBttl seconds\fP
This command specifies the default time\-to\-live, in seconds, for records to be added. The value
\fBnone\fP clears the default TTL.
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.TP
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.B \fBkey hmac:keyname secret\fP
This command specifies that all updates are to be TSIG\-signed using the
\fBkeyname\fP\-\fBsecret\fP pair. If \fBhmac\fP is specified, it sets
the signing algorithm in use. The default is \fBhmac\-md5\fP; if MD5
was disabled, the default is \fBhmac\-sha256\fP\&. The \fBkey\fP command overrides any key
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specified on the command line via \fB\-y\fP or \fB\-k\fP\&.
.TP
.B \fBgsstsig\fP
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This command uses GSS\-TSIG to sign the updates. This is equivalent to specifying
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\fB\-g\fP on the command line.
.TP
.B \fBoldgsstsig\fP
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This command uses the Windows 2000 version of GSS\-TSIG to sign the updates. This is
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equivalent to specifying \fB\-o\fP on the command line.
.TP
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.B \fBrealm [realm_name]\fP
When using GSS\-TSIG, this command specifies the use of \fBrealm_name\fP rather than the default realm
in \fBkrb5.conf\fP\&. If no realm is specified, the saved realm is
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cleared.
.TP
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.B \fBcheck\-names [yes_or_no]\fP
This command turns on or off check\-names processing on records to be added.
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Check\-names has no effect on prerequisites or records to be deleted.
By default check\-names processing is on. If check\-names processing
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fails, the record is not added to the UPDATE message.
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.TP
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.B \fBprereq nxdomain domain\-name\fP
This command requires that no resource record of any type exist with the name
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\fBdomain\-name\fP\&.
.TP
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.B \fBprereq yxdomain domain\-name\fP
This command requires that \fBdomain\-name\fP exist (as at least one resource
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record, of any type).
.TP
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.B \fBprereq nxrrset domain\-name class type\fP
This command requires that no resource record exist of the specified \fBtype\fP,
\fBclass\fP, and \fBdomain\-name\fP\&. If \fBclass\fP is omitted, IN (Internet)
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is assumed.
.TP
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.B \fBprereq yxrrset domain\-name class type\fP
This command requires that a resource record of the specified \fBtype\fP,
\fBclass\fP and \fBdomain\-name\fP exist. If \fBclass\fP is omitted, IN
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(internet) is assumed.
.TP
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.B \fBprereq yxrrset domain\-name class type data\fP
With this command, the \fBdata\fP from each set of prerequisites of this form sharing a
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common \fBtype\fP, \fBclass\fP, and \fBdomain\-name\fP are combined to form
a set of RRs. This set of RRs must exactly match the set of RRs
existing in the zone at the given \fBtype\fP, \fBclass\fP, and
\fBdomain\-name\fP\&. The \fBdata\fP are written in the standard text
representation of the resource record\(aqs RDATA.
.TP
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.B \fBupdate delete domain\-name ttl class type data\fP
This command deletes any resource records named \fBdomain\-name\fP\&. If \fBtype\fP and
\fBdata\fP are provided, only matching resource records are removed.
The Internet class is assumed if \fBclass\fP is not supplied. The
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\fBttl\fP is ignored, and is only allowed for compatibility.
.TP
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.B \fBupdate add domain\-name ttl class type data\fP
This command adds a new resource record with the specified \fBttl\fP, \fBclass\fP, and
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\fBdata\fP\&.
.TP
.B \fBshow\fP
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This command displays the current message, containing all of the prerequisites and
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updates specified since the last send.
.TP
.B \fBsend\fP
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This command sends the current message. This is equivalent to entering a blank
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line.
.TP
.B \fBanswer\fP
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This command displays the answer.
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.TP
.B \fBdebug\fP
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This command turns on debugging.
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.TP
.B \fBversion\fP
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This command prints the version number.
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.TP
.B \fBhelp\fP
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This command prints a list of commands.
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.UNINDENT
.sp
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Lines beginning with a semicolon (;) are comments and are ignored.
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.SH EXAMPLES
.sp
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The examples below show how \fBnsupdate\fP can be used to insert and
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delete resource records from the \fBexample.com\fP zone. Notice that the
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input in each example contains a trailing blank line, so that a group of
commands is sent as one dynamic update request to the primary name
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server for \fBexample.com\fP\&.
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
# nsupdate
> update delete oldhost.example.com A
> update add newhost.example.com 86400 A 172.16.1.1
> send
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
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Any A records for \fBoldhost.example.com\fP are deleted, and an A record
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for \fBnewhost.example.com\fP with IP address 172.16.1.1 is added. The
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newly added record has a TTL of 1 day (86400 seconds).
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.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
# nsupdate
> prereq nxdomain nickname.example.com
> update add nickname.example.com 86400 CNAME somehost.example.com
> send
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
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The prerequisite condition tells the name server to verify that there are
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no resource records of any type for \fBnickname.example.com\fP\&. If there
are, the update request fails. If this name does not exist, a CNAME for
it is added. This ensures that when the CNAME is added, it cannot
conflict with the long\-standing rule in \fI\%RFC 1034\fP that a name must not
exist as any other record type if it exists as a CNAME. (The rule has
been updated for DNSSEC in \fI\%RFC 2535\fP to allow CNAMEs to have RRSIG,
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DNSKEY, and NSEC records.)
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.SH FILES
.INDENT 0.0
.TP
.B \fB/etc/resolv.conf\fP
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Used to identify the default name server
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.TP
.B \fB/var/run/named/session.key\fP
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Sets the default TSIG key for use in local\-only mode
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.TP
.B \fBK{name}.+157.+{random}.key\fP
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Base\-64 encoding of the HMAC\-MD5 key created by \fBdnssec\-keygen\fP\&.
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.TP
.B \fBK{name}.+157.+{random}.private\fP
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Base\-64 encoding of the HMAC\-MD5 key created by \fBdnssec\-keygen\fP\&.
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.UNINDENT
.SH SEE ALSO
.sp
\fI\%RFC 2136\fP, \fI\%RFC 3007\fP, \fI\%RFC 2104\fP, \fI\%RFC 2845\fP, \fI\%RFC 1034\fP, \fI\%RFC 2535\fP, \fI\%RFC 2931\fP,
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\fBnamed(8)\fP, \fBtsig\-keygen(8)\fP, \fBdnssec\-keygen(8)\fP\&.
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.SH BUGS
.sp
The TSIG key is redundantly stored in two separate files. This is a
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consequence of \fBnsupdate\fP using the DST library for its cryptographic
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operations, and may change in future releases.
.SH AUTHOR
Internet Systems Consortium
.SH COPYRIGHT
2020, Internet Systems Consortium
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