Provided by: bind9-dnsutils_9.20.0-2ubuntu3_amd64 
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 an alternate DNSSEC root zone trust
anchor.
By default, keys that do not match the root zone name (.) are ignored. If an
alternate key name is desired, it can be specified using the +root option.
Note: When reading trust anchors, 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. This means that if the default key built
in to delv is revoked, delv must be updated to a newer version in order to continue
validating.
-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:
+cdflag, +nocdflag
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.
+class, +noclass
This option controls whether to display the CLASS when printing a record. The
default is to display the CLASS.
+hint=FILE, +nohint
This option specifies a filename from which to load root hints; this will be used
to find the root name servers when name server mode (delv +ns) is in use. If the
option is not specified, built-in root hints will be used.
+ns, +nons
This option toggles name server mode. When this option is in use, the delv process
instantiates a full recursive resolver, and uses that to look up the requested
query name and type. Turning on this option also activates +mtrace, +strace and
+rtrace, so that every iterative query will be logged, including the full response
messages from each authoritatve server. These logged messages will be written to
stdout rather than stderr as usual, so that the full trace can be captured more
easily.
This is intended to be similar to the behavior of dig +trace, but because it uses
the same code as named, it much more accurately replicates the behavior of a
recursive name server with a cold cache that is processing a recursive query.
+qmin[=MODE], +noqmin
When used with +ns, this option enables QNAME minimization mode. Valid options of
MODE are relaxed and strict. By default, QNAME minimization is disabled. If +qmin
is specified but MODE is omitted, then relaxed mode will be used.
+ttl, +nottl
This option controls whether to display the TTL when printing a record. The default
is to display the TTL.
+rtrace, +nortrace
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.
+mtrace, +nomtrace
This option toggles logging of messages received. 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.
+strace, +nostrace
This option toggles logging of messages sent. This produces a detailed dump of the
queries sent by delv in the process of carrying out the resolution and validation
process. Turning on this option also activates +mtrace.
This is equivalent to setting the debug level to 11 for the "packets" module of the
"resolver" logging category. Setting the systemwide debug level to 11 using the -d
option produces the same output, but affects other logging categories as well.
+vtrace, +novtrace
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.
+short, +noshort
This option toggles between verbose and terse answers. The default is to print the
answer in a verbose form.
+comments, +nocomments
This option toggles the display of comment lines in the output. The default is to
print comments.
+rrcomments, +norrcomments
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.
+crypto, +nocrypto
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
].
+trust, +notrust
This option controls whether to display the trust level when printing a record.
The default is to display the trust level.
+split[=W], +nosplit
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.
+all, +noall
This option sets or clears the display options +comments, +rrcomments, and +trust
as a group.
+multiline, +nomultiline
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.
+dnssec, +nodnssec
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.
+root[=ROOT], +noroot
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.
+tcp, +notcp
This option controls whether to use TCP when sending queries. The default is to use
UDP unless a truncated response has been received.
+unknownformat, +nounknownformat
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.
+yaml, +noyaml
This option prints response data in YAML format.
FILES
/etc/resolv.conf
SEE ALSO
dig(1), named(8), RFC 4034, RFC 4035, RFC 4431, RFC 5074, RFC 5155.
AUTHOR
Internet Systems Consortium
COPYRIGHT
2024, Internet Systems Consortium