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diff --git a/bin/nsupdate/nsupdate.rst b/bin/nsupdate/nsupdate.rst new file mode 100644 index 0000000..aad9b02 --- /dev/null +++ b/bin/nsupdate/nsupdate.rst @@ -0,0 +1,357 @@ +.. Copyright (C) Internet Systems Consortium, Inc. ("ISC") +.. +.. SPDX-License-Identifier: MPL-2.0 +.. +.. This Source Code Form is subject to the terms of the Mozilla Public +.. License, v. 2.0. If a copy of the MPL was not distributed with this +.. file, you can obtain one at https://mozilla.org/MPL/2.0/. +.. +.. See the COPYRIGHT file distributed with this work for additional +.. information regarding copyright ownership. + +.. highlight: console + +.. _man_nsupdate: + +nsupdate - dynamic DNS update utility +------------------------------------- + +Synopsis +~~~~~~~~ + +:program:`nsupdate` [**-d**] [**-D**] [**-i**] [**-L** level] [ [**-g**] | [**-o**] | [**-l**] | [**-y** [hmac:]keyname:secret] | [**-k** keyfile] ] [**-t** timeout] [**-u** udptimeout] [**-r** udpretries] [**-v**] [**-T**] [**-P**] [**-V**] [ [**-4**] | [**-6**] ] [filename] + +Description +~~~~~~~~~~~ + +``nsupdate`` is used to submit Dynamic DNS Update requests, as defined in +:rfc:`2136`, 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 ``nsupdate`` 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 +``nsupdate`` must be in the same zone. Requests are sent to the +zone's primary server, which is identified by the MNAME field of the +zone's SOA record. + +Transaction signatures can be used to authenticate the Dynamic DNS +updates. These use the TSIG resource record type described in :rfc:`2845`, +the SIG(0) record described in :rfc:`2535` and :rfc:`2931`, or GSS-TSIG as +described in :rfc:`3645`. + +TSIG relies on a shared secret that should only be known to ``nsupdate`` +and the name server. For instance, suitable ``key`` and ``server`` +statements are 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 is using TSIG +authentication. ``ddns-confgen`` can generate suitable +configuration fragments. ``nsupdate`` uses the ``-y`` or ``-k`` options +to provide the TSIG shared secret; these options are mutually exclusive. + +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. + +GSS-TSIG uses Kerberos credentials. Standard GSS-TSIG mode is switched +on with the ``-g`` flag. A non-standards-compliant variant of GSS-TSIG +used by Windows 2000 can be switched on with the ``-o`` flag. + +Options +~~~~~~~ + +``-4`` + This option sets use of IPv4 only. + +``-6`` + This option sets use of IPv6 only. + +``-d`` + This option sets debug mode, which provides tracing information about the update + requests that are made and the replies received from the name server. + +``-D`` + This option sets extra debug mode. + +``-i`` + This option forces interactive mode, even when standard input is not a terminal. + +``-k keyfile`` + This option indicates the file containing the TSIG authentication key. Keyfiles may be in + two formats: a single file containing a ``named.conf``-format ``key`` + statement, which may be generated automatically by ``ddns-confgen``; + or a pair of files whose names are of the format + ``K{name}.+157.+{random}.key`` and + ``K{name}.+157.+{random}.private``, which can be generated by + ``dnssec-keygen``. The ``-k`` option can also be used 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. + +``-l`` + This option sets local-host only mode, which sets the server address to localhost + (disabling the ``server`` so that the server address cannot be + overridden). Connections to the local server use a TSIG key + found in ``/var/run/named/session.key``, which is automatically + generated by ``named`` if any local ``primary`` zone has set + ``update-policy`` to ``local``. The location of this key file can be + overridden with the ``-k`` option. + +``-L level`` + This option sets the logging debug level. If zero, logging is disabled. + +``-p port`` + This option sets the port to use for connections to a name server. The default is + 53. + +``-P`` + This option prints the list of private BIND-specific resource record types whose + format is understood by ``nsupdate``. See also the ``-T`` option. + +``-r udpretries`` + This option sets the number of UDP retries. The default is 3. If zero, only one update + request is made. + +``-t timeout`` + 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. + +``-T`` + This option prints the list of IANA standard resource record types whose format is + understood by ``nsupdate``. ``nsupdate`` exits after the lists + are printed. The ``-T`` option can be combined with the ``-P`` + option. + + Other types can be entered using ``TYPEXXXXX`` where ``XXXXX`` is the + decimal value of the type with no leading zeros. The rdata, if + present, is parsed using the UNKNOWN rdata format, (<backslash> + <hash> <space> <length> <space> <hexstring>). + +``-u udptimeout`` + 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 + retries. + +``-v`` + This option specifies that TCP should be used even for small update requests. By default, ``nsupdate`` 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. TCP may + be preferable when a batch of update requests is made. + +``-V`` + This option prints the version number and exits. + +``-y [hmac:]keyname:secret`` + This option sets the literal TSIG authentication key. ``keyname`` is the name of the key, + and ``secret`` is the base64 encoded shared secret. ``hmac`` is the + name of the key algorithm; valid choices are ``hmac-md5``, + ``hmac-sha1``, ``hmac-sha224``, ``hmac-sha256``, ``hmac-sha384``, or + ``hmac-sha512``. If ``hmac`` is not specified, the default is + ``hmac-md5``, or if MD5 was disabled, ``hmac-sha256``. + + NOTE: 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 ps1 or in a history file maintained by + the user's shell. + +Input Format +~~~~~~~~~~~~ + +``nsupdate`` reads input from ``filename`` or standard input. Each +command is supplied on exactly one line of input. Some commands are for +administrative purposes; 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 are 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 either 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. + +The command formats and their meanings are as follows: + +``server servername port`` + This command sends all dynamic update requests to the name server ``servername``. + When no server statement is provided, ``nsupdate`` sends updates + to the primary server of the correct zone. The MNAME field of that + zone's SOA record identify the primary server for that zone. + ``port`` is the port number on ``servername`` where the dynamic + update requests are sent. If no port number is specified, the default + DNS port number of 53 is used. + + .. note:: This command has no effect when GSS-TSIG is in use. + +``local address port`` + This command sends all dynamic update requests using the local ``address``. When + no local statement is provided, ``nsupdate`` sends updates using + an address and port chosen by the system. ``port`` can also + be used to force requests to come from a specific port. If no port number + is specified, the system assigns one. + +``zone zonename`` + This command specifies that all updates are to be made to the zone ``zonename``. + If no ``zone`` statement is provided, ``nsupdate`` attempts to + determine the correct zone to update based on the rest of the input. + +``class classname`` + This command specifies the default class. If no ``class`` is specified, the default + class is ``IN``. + +``ttl seconds`` + This command specifies the default time-to-live, in seconds, for records to be added. The value + ``none`` clears the default TTL. + +``key hmac:keyname secret`` + This command specifies that all updates are to be TSIG-signed using the + ``keyname``-``secret`` pair. If ``hmac`` is specified, it sets + the signing algorithm in use. The default is ``hmac-md5``; if MD5 + was disabled, the default is ``hmac-sha256``. The ``key`` command overrides any key + specified on the command line via ``-y`` or ``-k``. + +``gsstsig`` + This command uses GSS-TSIG to sign the updates. This is equivalent to specifying + ``-g`` on the command line. + +``oldgsstsig`` + This command uses the Windows 2000 version of GSS-TSIG to sign the updates. This is + equivalent to specifying ``-o`` on the command line. + +``realm [realm_name]`` + When using GSS-TSIG, this command specifies the use of ``realm_name`` rather than the default realm + in ``krb5.conf``. If no realm is specified, the saved realm is + cleared. + +``check-names [yes_or_no]`` + This command turns on or off check-names processing on records to be added. + Check-names has no effect on prerequisites or records to be deleted. + By default check-names processing is on. If check-names processing + fails, the record is not added to the UPDATE message. + +``prereq nxdomain domain-name`` + This command requires that no resource record of any type exist with the name + ``domain-name``. + +``prereq yxdomain domain-name`` + This command requires that ``domain-name`` exist (as at least one resource + record, of any type). + +``prereq nxrrset domain-name class type`` + This command requires that no resource record exist of the specified ``type``, + ``class``, and ``domain-name``. If ``class`` is omitted, IN (Internet) + is assumed. + +``prereq yxrrset domain-name class type`` + This command requires that a resource record of the specified ``type``, + ``class`` and ``domain-name`` exist. If ``class`` is omitted, IN + (internet) is assumed. + +``prereq yxrrset domain-name class type data`` + With this command, the ``data`` from each set of prerequisites of this form sharing a + common ``type``, ``class``, and ``domain-name`` 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 ``type``, ``class``, and + ``domain-name``. The ``data`` are written in the standard text + representation of the resource record's RDATA. + +``update delete domain-name ttl class type data`` + This command deletes any resource records named ``domain-name``. If ``type`` and + ``data`` are provided, only matching resource records are removed. + The Internet class is assumed if ``class`` is not supplied. The + ``ttl`` is ignored, and is only allowed for compatibility. + +``update add domain-name ttl class type data`` + This command adds a new resource record with the specified ``ttl``, ``class``, and + ``data``. + +``show`` + This command displays the current message, containing all of the prerequisites and + updates specified since the last send. + +``send`` + This command sends the current message. This is equivalent to entering a blank + line. + +``answer`` + This command displays the answer. + +``debug`` + This command turns on debugging. + +``version`` + This command prints the version number. + +``help`` + This command prints a list of commands. + +Lines beginning with a semicolon (;) are comments and are ignored. + +Examples +~~~~~~~~ + +The examples below show how ``nsupdate`` can be used to insert and +delete resource records from the ``example.com`` zone. Notice that the +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 +server for ``example.com``. + +:: + + # nsupdate + > update delete oldhost.example.com A + > update add newhost.example.com 86400 A 172.16.1.1 + > send + +Any A records for ``oldhost.example.com`` are deleted, and an A record +for ``newhost.example.com`` with IP address 172.16.1.1 is added. The +newly added record has a TTL of 1 day (86400 seconds). + +:: + + # nsupdate + > prereq nxdomain nickname.example.com + > update add nickname.example.com 86400 CNAME somehost.example.com + > send + +The prerequisite condition tells the name server to verify that there are +no resource records of any type for ``nickname.example.com``. 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 :rfc:`1034` 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 :rfc:`2535` to allow CNAMEs to have RRSIG, +DNSKEY, and NSEC records.) + +Files +~~~~~ + +``/etc/resolv.conf`` + Used to identify the default name server + +``/var/run/named/session.key`` + Sets the default TSIG key for use in local-only mode + +``K{name}.+157.+{random}.key`` + Base-64 encoding of the HMAC-MD5 key created by ``dnssec-keygen``. + +``K{name}.+157.+{random}.private`` + Base-64 encoding of the HMAC-MD5 key created by ``dnssec-keygen``. + +See Also +~~~~~~~~ + +:rfc:`2136`, :rfc:`3007`, :rfc:`2104`, :rfc:`2845`, :rfc:`1034`, :rfc:`2535`, :rfc:`2931`, +:manpage:`named(8)`, :manpage:`ddns-confgen(8)`, :manpage:`dnssec-keygen(8)`. + +Bugs +~~~~ + +The TSIG key is redundantly stored in two separate files. This is a +consequence of ``nsupdate`` using the DST library for its cryptographic +operations, and may change in future releases. |