nsupdate9 Command

Purpose

Dynamic DNS update utility.

Syntax

nsupdate9 [-d] [-y [ hmac: ] keyname: secret | -k keyfile] [ -t timeout ] [ -u udptimeout ] [ -r udpretries ] [-v] [filename]

Description

The nsupdate9 command is used to submit Dynamic DNS Update requests as defined in RFC2136 to a name server. This allows resource records to be added or 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.

Zones that are under dynamic control via nsupdate9 or a DHCP server should not be edited by hand. Manual edits could conflict with dynamic updates and cause data to be lost.

The resource records that are dynamically added or removed with nsupdate9 have to be in the same zone. Requests are sent to the zone's master server. This is identified by the MNAME field of the zone's SOA record.

The -d option makes nsupdate9 operate in debug mode. This provides tracing information about the update requests that are made and the replies received from the name server.

Transaction signatures can be used to authenticate the Dynamic DNS updates. These use the TSIG resource record type described in RFC2845 or the SIG(0) record described in RFC3535 and RFC2931. The signatures rely on a shared secret that should only be known to nsupdate9 and the name server. Currently, the only supported encryption algorithm for TSIG is HMAC-MD5, which is defined in RFC 2104. Once other algorithms are defined for TSIG, applications will need to ensure they select the appropriate algorithm as well as the key when authenticating each other. For instance suitable key and server statements would be added to /etc/named.conf so that the name server can associate the appropriate secret key and algorithm with the IP address of the client application that will be using TSIG authentication. 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. nsupdate9 does not read /etc/named.conf.

nsupdate9 uses the -y or -k option to provide the shared secret needed to generate a TSIG record for authenticating Dynamic DNS update requests. The default type is HMAC-MD5. These options are mutually exclusive. With the -k option, nsupdate9 reads the shared secret from the file keyfile, whose name is of the form K{name}.+157.+{random}.private. For historical reasons, the file K{name}.+157.+{random}.key must also be present. When the -y option is used, a signature is generated from [ hmac: ] keyname:secret. keyname is the name of the key, and secret is the base64 encoded shared secret. Use of the -y option is discouraged because the shared secret is supplied as a command line argument in clear text. This may be visible in the output from ps(1) or in a history file maintained by the user's shell.

You can also use the -k flag to specify a SIG(0) key used to authenticate Dynamic DNS update requests. In this case, the key specified is not an HMAC-MD5 key.

By default nsupdate9 uses UDP to send update requests to the name server unless they are too large to fit in a UDP request in which case TCP is used. The -v option makes nsupdate9 use a TCP connection. This may be preferable when a batch of update requests is made.

Flags

Parameters

Input Format

nsupdate9 reads input from the file filename or standard input. Each command is supplied on exactly one line of input. Some commands are for administrative purposes. The others are either update instructions or 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 entire update request is to succeed. Updates will be rejected if the tests for the prerequisite conditions fail.

Every update request consists of zero or more prerequisites and zero or more updates. This allows a suitably authenticated update request to proceed if some specified resource records are present or missing from the zone. A blank input line (or the send command) causes the accumulated commands to be sent as one Dynamic DNS update request to the name server.

Security

Attention RBAC users and Trusted AIX® users: This command can perform privileged operations. Only privileged users can run privileged operations. For more information about authorizations and privileges, see Privileged Command Database in Security. For a list of privileges and the authorizations associated with this command, see the lssecattr command or the getcmdattr subcommand.

Examples

# nsupdate9
> update delete oldhost.example.com A
> update add newhost.example.com 86400 A 172.16.1.1
>

# nsupdate9 
> prereq nxdomain nickname.example.com 
> update add nickname.example.com CNAME somehost.example.com 
> send

# nsupdate9
> update delete 61.26.31.9.in-addr.arpa 0 IN PTR
> update add 61.26.31.9.in-addr.arpa 86400 IN PTR newhost.example.com.                          

Files