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<refentry xmlns:db="http://docbook.org/ns/docbook" version="5.0" xml:id="man.delv">
  <info>
    <date>2014-04-23</date>
  </info>
  <refentryinfo>
    <corpname>ISC</corpname>
    <corpauthor>Internet Systems Consortium, Inc.</corpauthor>
  </refentryinfo>

  <refmeta>
    <refentrytitle>delv</refentrytitle>
    <manvolnum>1</manvolnum>
    <refmiscinfo>BIND9</refmiscinfo>
  </refmeta>

  <refnamediv>
    <refname>delv</refname>
    <refpurpose>DNS lookup and validation utility</refpurpose>
  </refnamediv>

  <docinfo>
    <copyright>
      <year>2014</year>
      <year>2015</year>
      <year>2016</year>
      <year>2017</year>
      <year>2018</year>
      <year>2019</year>
      <holder>Internet Systems Consortium, Inc. ("ISC")</holder>
    </copyright>
  </docinfo>

  <refsynopsisdiv>
    <cmdsynopsis sepchar=" ">
      <command>delv</command>
      <arg choice="opt" rep="norepeat">@server</arg>
      <group choice="opt" rep="norepeat">
	<arg choice="opt" rep="norepeat"><option>-4</option></arg>
	<arg choice="opt" rep="norepeat"><option>-6</option></arg>
      </group>
      <arg choice="opt" rep="norepeat"><option>-a <replaceable class="parameter">anchor-file</replaceable></option></arg>
      <arg choice="opt" rep="norepeat"><option>-b <replaceable class="parameter">address</replaceable></option></arg>
      <arg choice="opt" rep="norepeat"><option>-c <replaceable class="parameter">class</replaceable></option></arg>
      <arg choice="opt" rep="norepeat"><option>-d <replaceable class="parameter">level</replaceable></option></arg>
      <arg choice="opt" rep="norepeat"><option>-i</option></arg>
      <arg choice="opt" rep="norepeat"><option>-m</option></arg>
      <arg choice="opt" rep="norepeat"><option>-p <replaceable class="parameter">port#</replaceable></option></arg>
      <arg choice="opt" rep="norepeat"><option>-q <replaceable class="parameter">name</replaceable></option></arg>
      <arg choice="opt" rep="norepeat"><option>-t <replaceable class="parameter">type</replaceable></option></arg>
      <arg choice="opt" rep="norepeat"><option>-x <replaceable class="parameter">addr</replaceable></option></arg>
      <arg choice="opt" rep="norepeat">name</arg>
      <arg choice="opt" rep="norepeat">type</arg>
      <arg choice="opt" rep="norepeat">class</arg>
      <arg choice="opt" rep="repeat">queryopt</arg>
    </cmdsynopsis>

    <cmdsynopsis sepchar=" ">
      <command>delv</command>
      <arg choice="opt" rep="norepeat"><option>-h</option></arg>
    </cmdsynopsis>

    <cmdsynopsis sepchar=" ">
      <command>delv</command>
      <arg choice="opt" rep="norepeat"><option>-v</option></arg>
    </cmdsynopsis>

    <cmdsynopsis sepchar=" ">
      <command>delv</command>
      <arg choice="opt" rep="repeat">queryopt</arg>
      <arg choice="opt" rep="repeat">query</arg>
    </cmdsynopsis>
  </refsynopsisdiv>

  <refsection><info><title>DESCRIPTION</title></info>

    <para><command>delv</command>
      is a tool for sending
      DNS queries and validating the results, using the same internal
      resolver and validator logic as <command>named</command>.
    </para>
    <para>
      <command>delv</command> will send to a specified name server all
      queries needed to fetch and validate the requested data; this
      includes the original requested query, subsequent queries to follow
      CNAME or DNAME chains, and queries for DNSKEY, DS and DLV records
      to establish a chain of trust for DNSSEC validation.
      It does not perform iterative resolution, but simulates the
      behavior of a name server configured for DNSSEC validating and
      forwarding.
    </para>
    <para>
      By default, responses are validated using built-in DNSSEC trust
      anchor for the root zone (".").  Records returned by
      <command>delv</command> are either fully validated or
      were not signed.  If validation fails, an explanation of
      the failure is included in the output; the validation process
      can be traced in detail.  Because <command>delv</command> does
      not rely on an external server to carry out validation, it can
      be used to check the validity of DNS responses in environments
      where local name servers may not be trustworthy.
    </para>
    <para>
      Unless it is told to query a specific name server,
      <command>delv</command> will try each of the servers listed in
      <filename>/etc/resolv.conf</filename>. If no usable server
      addresses are found, <command>delv</command> will send
      queries to the localhost addresses (127.0.0.1 for IPv4, ::1
      for IPv6).
    </para>
    <para>
      When no command line arguments or options are given,
      <command>delv</command> will perform an NS query for "."
      (the root zone).
    </para>
  </refsection>

  <refsection><info><title>SIMPLE USAGE</title></info>


    <para>
      A typical invocation of <command>delv</command> looks like:
      <programlisting> delv @server name type </programlisting>
      where:

      <variablelist>
	<varlistentry>
	  <term><constant>server</constant></term>
	  <listitem>
	    <para>
	      is the name or IP address of the name server to query.  This
	      can be an IPv4 address in dotted-decimal notation or an IPv6
	      address in colon-delimited notation.  When the supplied
	      <parameter>server</parameter> argument is a hostname,
	      <command>delv</command> resolves that name before
	      querying that name server (note, however, that this
	      initial lookup is <emphasis>not</emphasis> validated
	      by DNSSEC).
	    </para>
	    <para>
	      If no <parameter>server</parameter> argument is
	      provided, <command>delv</command> consults
	      <filename>/etc/resolv.conf</filename>; if an
	      address is found there, it queries the name server at
	      that address. If either of the <option>-4</option> or
	      <option>-6</option> options are in use, then
	      only addresses for the corresponding transport
	      will be tried.  If no usable addresses are found,
	      <command>delv</command> will send queries to
	      the localhost addresses (127.0.0.1 for IPv4,
	      ::1 for IPv6).
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><constant>name</constant></term>
	  <listitem>
	    <para>
	      is the domain name to be looked up.
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><constant>type</constant></term>
	  <listitem>
	    <para>
	      indicates what type of query is required &mdash;
	      ANY, A, MX, etc.
	      <parameter>type</parameter> can be any valid query
	      type.  If no
	      <parameter>type</parameter> argument is supplied,
	      <command>delv</command> will perform a lookup for an
	      A record.
	    </para>
	  </listitem>
	</varlistentry>

      </variablelist>
    </para>

  </refsection>

  <refsection><info><title>OPTIONS</title></info>

    <variablelist>

      <varlistentry>
	<term>-a <replaceable class="parameter">anchor-file</replaceable></term>
	<listitem>
	  <para>
	    Specifies a file from which to read DNSSEC trust anchors.
	    The default is <filename>/etc/bind.keys</filename>, which
	    is included with <acronym>BIND</acronym> 9 and contains
	    one or more trust anchors for the root zone (".").
	  </para>
	  <para>
	    Keys that do not match the root zone name are ignored.
            An alternate key name can be specified using the
	    <option>+root=NAME</option> options. DNSSEC Lookaside
            Validation can also be turned on by using the
	    <option>+dlv=NAME</option> to specify the name of a
            zone containing DLV records.
	  </para>
	  <para>
	    Note: When reading the trust anchor file,
	    <command>delv</command> treats <option>managed-keys</option>
	    statements and <option>trusted-keys</option> statements
	    identically.  That is, for a managed key, it is the
	    <emphasis>initial</emphasis> key that is trusted; RFC 5011
	    key management is not supported. <command>delv</command>
	    will not consult the managed-keys database maintained by
	    <command>named</command>. This means that if either of the
	    keys in <filename>/etc/bind.keys</filename> is revoked
	    and rolled over, it will be necessary to update
	    <filename>/etc/bind.keys</filename> to use DNSSEC
	    validation in <command>delv</command>.
	  </para>
	</listitem>
      </varlistentry>

      <varlistentry>
	<term>-b  <replaceable class="parameter">address</replaceable></term>
	<listitem>
	  <para>
	    Sets the source IP address of the query to
	    <parameter>address</parameter>.  This must be a valid address
	    on one of the host's network interfaces or "0.0.0.0" or "::".
	    An optional source port may be specified by appending
	    "#&lt;port&gt;"
	  </para>
	</listitem>
      </varlistentry>

      <varlistentry>
	<term>-c <replaceable class="parameter">class</replaceable></term>
	<listitem>
	  <para>
	    Sets the query class for the requested data. Currently,
	    only class "IN" is supported in <command>delv</command>
	    and any other value is ignored.
	  </para>
	</listitem>
      </varlistentry>

      <varlistentry>
	<term>-d <replaceable class="parameter">level</replaceable></term>
	<listitem>
	  <para>
	    Set the systemwide debug level to <option>level</option>.
	    The allowed range is from 0 to 99.
	    The default is 0 (no debugging).
	    Debugging traces from <command>delv</command> become
	    more verbose as the debug level increases.
	    See the <option>+mtrace</option>, <option>+rtrace</option>,
	    and <option>+vtrace</option> options below for additional
	    debugging details.
	  </para>
	</listitem>
      </varlistentry>

      <varlistentry>
	<term>-h</term>
	<listitem>
	  <para>
	    Display the <command>delv</command> help usage output and exit.
	  </para>
	</listitem>
      </varlistentry>

      <varlistentry>
	<term>-i</term>
	<listitem>
	  <para>
	    Insecure mode. This disables internal DNSSEC validation.
	    (Note, however, this does not set the CD bit on upstream
	    queries. If the server being queried is performing DNSSEC
	    validation, then it will not return invalid data; this
	    can cause <command>delv</command> to time out. When it
	    is necessary to examine invalid data to debug a DNSSEC
	    problem, use <command>dig +cd</command>.)
	  </para>
	</listitem>
      </varlistentry>

      <varlistentry>
	<term>-m</term>
	<listitem>
	  <para>
	    Enables memory usage debugging.
	  </para>
	</listitem>
      </varlistentry>

      <varlistentry>
	<term>-p <replaceable class="parameter">port#</replaceable></term>
	<listitem>
	  <para>
	    Specifies a destination port to use for queries instead of
	    the standard DNS port number 53.  This option would be used
	    with a name server that has been configured to listen
	    for queries on a non-standard port number.
	  </para>
	</listitem>
      </varlistentry>

      <varlistentry>
	<term>-q <replaceable class="parameter">name</replaceable></term>
	<listitem>
	  <para>
	    Sets the query name to <parameter>name</parameter>.
	    While the query name can be specified without using the
	    <option>-q</option>, it is sometimes necessary to disambiguate
	    names from types or classes (for example, when looking up the
	    name "ns", which could be misinterpreted as the type NS,
	    or "ch", which could be misinterpreted as class CH).
	  </para>
	</listitem>
      </varlistentry>

      <varlistentry>
	<term>-t <replaceable class="parameter">type</replaceable></term>
	<listitem>
	  <para>
	    Sets the query type to <parameter>type</parameter>, which
	    can be any valid query type supported in BIND 9 except
	    for zone transfer types AXFR and IXFR. As with
	    <option>-q</option>, this is useful to distinguish
	    query name type or class when they are ambiguous.
	    it is sometimes necessary to disambiguate names from types.
	  </para>
	  <para>
	    The default query type is "A", unless the <option>-x</option>
	    option is supplied to indicate a reverse lookup, in which case
	    it is "PTR".
	  </para>
	</listitem>
      </varlistentry>

      <varlistentry>
	<term>-v</term>
	<listitem>
	  <para>
	    Print the <command>delv</command> version and exit.
	  </para>
	</listitem>
      </varlistentry>

      <varlistentry>
	<term>-x <replaceable class="parameter">addr</replaceable></term>
	<listitem>
	  <para>
	    Performs a reverse lookup, mapping an addresses to
	    a name.  <parameter>addr</parameter> is an IPv4 address in
	    dotted-decimal notation, or a colon-delimited IPv6 address.
	    When <option>-x</option> is used, there is no need to provide
	    the <parameter>name</parameter> or <parameter>type</parameter>
	    arguments.  <command>delv</command> automatically performs a
	    lookup for a name like <literal>11.12.13.10.in-addr.arpa</literal>
	    and sets the query type to PTR.  IPv6 addresses are looked up
	    using nibble format under the IP6.ARPA domain.
	  </para>
	</listitem>
      </varlistentry>

      <varlistentry>
	<term>-4</term>
	<listitem>
	  <para>
	    Forces <command>delv</command> to only use IPv4.
	  </para>
	</listitem>
      </varlistentry>

      <varlistentry>
	<term>-6</term>
	<listitem>
	  <para>
	    Forces <command>delv</command> to only use IPv6.
	  </para>
	</listitem>
      </varlistentry>

    </variablelist>
  </refsection>

  <refsection><info><title>QUERY OPTIONS</title></info>


    <para><command>delv</command>
      provides a number of query options which affect the way results are
      displayed, and in some cases the way lookups are performed.
    </para>

    <para>
      Each query option is identified by a keyword preceded by a plus sign
      (<literal>+</literal>).  Some keywords set or reset an
      option.  These may be preceded by the string
      <literal>no</literal> to negate the meaning of that keyword.
      Other keywords assign values to options like the timeout interval.
      They have the form <option>+keyword=value</option>.
      The query options are:

      <variablelist>
	<varlistentry>
	  <term><option>+[no]cdflag</option></term>
	  <listitem>
	    <para>
	      Controls whether to set the CD (checking disabled) bit in
	      queries sent by <command>delv</command>. This may be useful
	      when troubleshooting DNSSEC problems from behind a validating
	      resolver. A validating resolver will block invalid responses,
	      making it difficult to retrieve them for analysis. Setting
	      the CD flag on queries will cause the resolver to return
	      invalid responses, which <command>delv</command> can then
	      validate internally and report the errors in detail.
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>+[no]class</option></term>
	  <listitem>
	    <para>
	      Controls whether to display the CLASS when printing
	      a record. The default is to display the CLASS.
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>+[no]ttl</option></term>
	  <listitem>
	    <para>
	      Controls whether to display the TTL when printing
	      a record. The default is to display the TTL.
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>+[no]rtrace</option></term>
	  <listitem>
	    <para>
	      Toggle resolver fetch logging. This reports the
	      name and type of each query sent by <command>delv</command>
	      in the process of carrying out the resolution and validation
	      process: this includes including the original query and
	      all subsequent queries to follow CNAMEs and to establish a
	      chain of trust for DNSSEC validation.
	    </para>
	    <para>
	      This is equivalent to setting the debug level to 1 in
	      the "resolver" logging category. Setting the systemwide
	      debug level to 1 using the <option>-d</option> option will
	      product the same output (but will affect other logging
	      categories as well).
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>+[no]mtrace</option></term>
	  <listitem>
	    <para>
	      Toggle message logging. This produces a detailed dump of
	      the responses received by <command>delv</command> in the
	      process of carrying out the resolution and validation process.
	    </para>
	    <para>
	      This is equivalent to setting the debug level to 10
	      for the "packets" module of the "resolver" logging
	      category. Setting the systemwide debug level to 10 using
	      the <option>-d</option> option will produce the same output
	      (but will affect other logging categories as well).
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>+[no]vtrace</option></term>
	  <listitem>
	    <para>
	      Toggle validation logging. This shows the internal
	      process of the validator as it determines whether an
	      answer is validly signed, unsigned, or invalid.
	    </para>
	    <para>
	      This is equivalent to setting the debug level to 3
	      for the "validator" module of the "dnssec" logging
	      category. Setting the systemwide debug level to 3 using
	      the <option>-d</option> option will produce the same output
	      (but will affect other logging categories as well).
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>+[no]short</option></term>
	  <listitem>
	    <para>
	      Provide a terse answer.  The default is to print the answer in a
	      verbose form.
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>+[no]comments</option></term>
	  <listitem>
	    <para>
	      Toggle the display of comment lines in the output.  The default
	      is to print comments.
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>+[no]rrcomments</option></term>
	  <listitem>
	    <para>
	      Toggle the display of per-record comments in the output (for
	      example, human-readable key information about DNSKEY records).
	      The default is to print per-record comments.
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>+[no]crypto</option></term>
	  <listitem>
	    <para>
	      Toggle the display of cryptographic fields in DNSSEC records.
	      The contents of these field are unnecessary to debug most DNSSEC
	      validation failures and removing them makes it easier to see
	      the common failures.  The default is to display the fields.
	      When omitted they are replaced by the string "[omitted]" or
	      in the DNSKEY case the key id is displayed as the replacement,
	      e.g. "[ key id = value ]".
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>+[no]trust</option></term>
	  <listitem>
	    <para>
	      Controls whether to display the trust level when printing
	      a record. The default is to display the trust level.
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>+[no]split[=W]</option></term>
	  <listitem>
	    <para>
	      Split long hex- or base64-formatted fields in resource
	      records into chunks of <parameter>W</parameter> characters
	      (where <parameter>W</parameter> is rounded up to the nearest
	      multiple of 4).
	      <parameter>+nosplit</parameter> or
	      <parameter>+split=0</parameter> causes fields not to be
	      split at all.  The default is 56 characters, or 44 characters
	      when multiline mode is active.
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>+[no]all</option></term>
	  <listitem>
	    <para>
	      Set or clear the display options
	      <option>+[no]comments</option>,
	      <option>+[no]rrcomments</option>, and
	      <option>+[no]trust</option> as a group.
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>+[no]multiline</option></term>
	  <listitem>
	    <para>
	      Print long records (such as RRSIG, DNSKEY, and SOA records)
	      in a verbose multi-line format with human-readable comments.
	      The default is to print each record on a single line, to
	      facilitate machine parsing of the <command>delv</command>
	      output.
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>+[no]dnssec</option></term>
	  <listitem>
	    <para>
	      Indicates whether to display RRSIG records in the
	      <command>delv</command> output.  The default is to
	      do so.  Note that (unlike in <command>dig</command>)
	      this does <emphasis>not</emphasis> control whether to
	      request DNSSEC records or whether to validate them.
	      DNSSEC records are always requested, and validation
	      will always occur unless suppressed by the use of
	      <option>-i</option> or <option>+noroot</option> and
	      <option>+nodlv</option>.
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>+[no]root[=ROOT]</option></term>
	  <listitem>
	    <para>
	      Indicates whether to perform conventional (non-lookaside)
	      DNSSEC validation, and if so, specifies the
	      name of a trust anchor.  The default is to validate using
	      a trust anchor of "." (the root zone), for which there is
	      a built-in key.  If specifying a different trust anchor,
	      then <option>-a</option> must be used to specify a file
	      containing the key.
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>+[no]dlv[=DLV]</option></term>
	  <listitem>
	    <para>
	      Indicates whether to perform DNSSEC lookaside validation,
	      and if so, specifies the name of the DLV trust anchor.
	      The <option>-a</option> option must also be used to specify
              a file containing the DLV key.
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>+[no]tcp</option></term>
	  <listitem>
	    <para>
	      Controls whether to use TCP when sending queries.
	      The default is to use UDP unless a truncated
	      response has been received.
	    </para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term><option>+[no]unknownformat</option></term>
	  <listitem>
	    <para>
	      Print all RDATA in unknown RR type presentation format
	      (RFC 3597). The default is to print RDATA for known types
	      in the type's presentation format.
	    </para>
	  </listitem>
	</varlistentry>
      </variablelist>

    </para>
  </refsection>

  <refsection><info><title>FILES</title></info>

    <para><filename>/etc/bind.keys</filename></para>
    <para><filename>/etc/resolv.conf</filename></para>
  </refsection>

  <refsection><info><title>SEE ALSO</title></info>

    <para><citerefentry>
	<refentrytitle>dig</refentrytitle><manvolnum>1</manvolnum>
      </citerefentry>,
      <citerefentry>
	<refentrytitle>named</refentrytitle><manvolnum>8</manvolnum>
      </citerefentry>,
      <citetitle>RFC4034</citetitle>,
      <citetitle>RFC4035</citetitle>,
      <citetitle>RFC4431</citetitle>,
      <citetitle>RFC5074</citetitle>,
      <citetitle>RFC5155</citetitle>.
    </para>
  </refsection>

</refentry>
