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 option.

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:

+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.

+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 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.

+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/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

2025, Internet Systems Consortium

9.18.34 2025-02-11 DELV(1)