Updated: 2021/Apr/14


DELV(1)                             BIND 9                             DELV(1)



NAME
       delv - DNS lookup and validation utility

SYNOPSIS
       delv [@server] [ [-4] | [-6] ] [-a anchor-file] [-b address] [-c class]
       [-d level] [-i] [-m] [-p port#] [-q name] [-t type] [-x addr] [name]
       [type] [class] [queryopt...]

       delv [-h]

       delv [-v]

       delv [queryopt...] [query...]

DESCRIPTION
       delv is a tool for sending DNS queries and validating the results,
       using the same internal resolver and validator logic as named.

       delv sends 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, queries for
       DNSKEY, and DS 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.

       By default, responses are validated using the built-in DNSSEC trust
       anchor for the root zone ("."). Records returned by delv 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 delv 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.

       Unless it is told to query a specific name server, delv tries each of
       the servers listed in /etc/resolv.conf. If no usable server addresses
       are found, delv sends queries to the localhost addresses (127.0.0.1 for
       IPv4, ::1 for IPv6).

       When no command-line arguments or options are given, delv performs an
       NS query for "." (the root zone).

SIMPLE USAGE
       A typical invocation of delv looks like:

          delv @server name type

       where:

       server 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 server argument
              is a hostname, delv resolves that name before querying that name
              server (note, however, that this initial lookup is not validated
              by DNSSEC).

              If no server argument is provided, delv consults
              /etc/resolv.conf; if an address is found there, it queries the
              name server at that address. If either of the -4 or -6 options
              is in use, then only addresses for the corresponding transport
              are tried. If no usable addresses are found, delv sends queries
              to the localhost addresses (127.0.0.1 for IPv4, ::1 for IPv6).

       name   is the domain name to be looked up.

       type   indicates what type of query is required - ANY, A, MX, etc.
              type can be any valid query type. If no type argument is
              supplied, delv performs a lookup for an A record.

OPTIONS

       -a anchor-file
              This option specifies a file from which to read DNSSEC trust
              anchors. The default is /etc/bind.keys, which is included with
              BIND 9 and contains one or more trust anchors for the root zone
              (".").

              Keys that do not match the root zone name are ignored. An
              alternate key name can be specified using the +root=NAME
              options.

              Note: When reading the trust anchor file, delv treats
              trust-anchors, initial-key, and static-key identically. That is,
              for a managed key, it is the initial key that is trusted; RFC
              5011 key management is not supported. delv does not consult the
              managed-keys database maintained by named, which means that if
              either of the keys in /etc/bind.keys is revoked and rolled over,
              /etc/bind.keys must be updated to use DNSSEC validation in delv.

       -b address
              This option sets the source IP address of the query to address.
              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 #<port>

       -c class
              This option sets the query class for the requested data.
              Currently, only class "IN" is supported in delv and any other
              value is ignored.

       -d level
              This option sets the systemwide debug level to level. The
              allowed range is from 0 to 99. The default is 0 (no debugging).
              Debugging traces from delv become more verbose as the debug
              level increases. See the +mtrace, +rtrace, and +vtrace options
              below for additional debugging details.

       -h     This option displays the delv help usage output and exits.

       -i     This option sets insecure mode, which disables internal DNSSEC
              validation. (Note, however, that this does not set the CD bit on
              upstream queries. If the server being queried is performing
              DNSSEC validation, then it does not return invalid data; this
              can cause delv to time out. When it is necessary to examine
              invalid data to debug a DNSSEC problem, use dig +cd.)

       -m     This option enables memory usage debugging.

       -p port#
              This option specifies a destination port to use for queries,
              instead of the standard DNS port number 53. This option is used
              with a name server that has been configured to listen for
              queries on a non-standard port number.

       -q name
              This option sets the query name to name. While the query name
              can be specified without using the -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).

       -t type
              This option sets the query type to type, which can be any valid
              query type supported in BIND 9 except for zone transfer types
              AXFR and IXFR. As with -q, this is useful to distinguish
              query-name types or classes when they are ambiguous. It is
              sometimes necessary to disambiguate names from types.

              The default query type is "A", unless the -x option is supplied
              to indicate a reverse lookup, in which case it is "PTR".

       -v     This option prints the delv version and exits.

       -x addr
              This option performs a reverse lookup, mapping an address to a
              name. addr is an IPv4 address in dotted-decimal notation, or a
              colon-delimited IPv6 address. When -x is used, there is no need
              to provide the name or type arguments; delv automatically
              performs a lookup for a name like 11.12.13.10.in-addr.arpa and
              sets the query type to PTR. IPv6 addresses are looked up using
              nibble format under the IP6.ARPA domain.

       -4     This option forces delv to only use IPv4.

       -6     This option forces delv to only use IPv6.

QUERY OPTIONS
       delv provides a number of query options which affect the way results
       are displayed, and in some cases the way lookups are performed.

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

       +[no]cdflag
              This option controls whether to set the CD (checking disabled)
              bit in queries sent by delv. This may be useful when
              troubleshooting DNSSEC problems from behind a validating
              resolver. A validating resolver blocks invalid responses, making
              it difficult to retrieve them for analysis. Setting the CD flag
              on queries causes the resolver to return invalid responses,
              which delv can then validate internally and report the errors in
              detail.

       +[no]class
              This option controls whether to display the CLASS when printing
              a record. The default is to display the CLASS.

       +[no]ttl
              This option controls whether to display the TTL when printing a
              record. The default is to display the TTL.

       +[no]rtrace
              This option toggles resolver fetch logging. This reports the
              name and type of each query sent by delv in the process of
              carrying out the resolution and validation process, including
              the original query and all subsequent queries to follow CNAMEs
              and to establish a chain of trust for DNSSEC validation.

              This is equivalent to setting the debug level to 1 in the
              "resolver" logging category. Setting the systemwide debug level
              to 1 using the -d option produces the same output, but affects
              other logging categories as well.

       +[no]mtrace
              This option toggles message logging. This produces a detailed
              dump of the responses received by delv in the process of
              carrying out the resolution and validation process.

              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 -d option produces the
              same output, but affects other logging categories as well.

       +[no]vtrace
              This option toggles validation logging. This shows the internal
              process of the validator as it determines whether an answer is
              validly signed, unsigned, or invalid.

              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 -d option produces the
              same output, but affects other logging categories as well.

       +[no]short
              This option toggles between verbose and terse answers. The
              default is to print the answer in a verbose form.

       +[no]comments
              This option toggles the display of comment lines in the output.
              The default is to print comments.

       +[no]rrcomments
              This option toggles 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.

       +[no]crypto
              This option toggles the display of cryptographic fields in
              DNSSEC records. The contents of these fields 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 ].

       +[no]trust
              This option controls whether to display the trust level when
              printing a record.  The default is to display the trust level.

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

       +[no]all
              This option sets or clears the display options +[no]comments,
              +[no]rrcomments, and +[no]trust as a group.

       +[no]multiline
              This option prints 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 delv output.

       +[no]dnssec
              This option indicates whether to display RRSIG records in the
              delv output.  The default is to do so. Note that (unlike in dig)
              this does not control whether to request DNSSEC records or to
              validate them. DNSSEC records are always requested, and
              validation always occurs unless suppressed by the use of -i or
              +noroot.

       +[no]root[=ROOT]
              This option indicates whether to perform conventional 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 -a must be used to specify a file
              containing the key.

       +[no]tcp
              This option controls whether to use TCP when sending queries.
              The default is to use UDP unless a truncated response has been
              received.

       +[no]unknownformat
              This option prints 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.

       +[no]yaml
              This option prints response data in YAML format.

FILES
       /etc/bind.keys

       /etc/resolv.conf

SEE ALSO
       dig(1), named(8), RFC 4034, RFC 4035, RFC 4431, RFC 5074, RFC 5155.

AUTHOR
       Internet Systems Consortium

COPYRIGHT
       2021, Internet Systems Consortium



9.16.12                                                                DELV(1)