DELV(1) BIND9 DELV(1)
delv - DNS lookup and validation utility
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 [queryopt...] [query...]
delv (Domain Entity Lookup & Validation) is a tool for sending DNS
queries and validating the results, using the the same internal resolver
and validator logic as named.
delv 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
By default, responses are validated using built-in DNSSEC trust anchors
for the root zone (".") and for the ISC DNSSEC lookaside validation zone
("dlv.isc.org"). 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 will try each of
the servers listed in /etc/resolv.conf. If no usable server addresses are
found, delv will send queries to the localhost addresses (127.0.0.1 for
IPv4, ::1 for IPv6).
When no command line arguments or options are given, delv will perform an
NS query for "." (the root zone).
A typical invocation of delv looks like:
delv @server name type
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 are in use, then only
addresses for the corresponding transport will be tried. If no usable
addresses are found, delv will send queries to the localhost
addresses (127.0.0.1 for IPv4, ::1 for IPv6).
is the domain name to be looked up.
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 will
perform a lookup for an A record.
Specifies a file from which to read DNSSEC trust anchors. The default
is /etc/bind.keys, which is included with BIND 9 and contains trust
anchors for the root zone (".") and for the ISC DNSSEC lookaside
validation zone ("dlv.isc.org").
Keys that do not match the root or DLV trust-anchor names are
ignored; these key names can be overridden using the +dlv=NAME or
Note: When reading the trust anchor file, delv treats managed-keys
statements and trusted-keys statements identically. That is, for a
managed key, it is the initial key that is trusted; RFC 5011 key
management is not supported. delv will not consult the managed-keys
database maintained by named. This means that if either of the keys
in /etc/bind.keys is revoked and rolled over, it will be necessary to
update /etc/bind.keys to use DNSSEC validation in delv.
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>"
Sets the query class for the requested data. Currently, only class
"IN" is supported in delv and any other value is ignored.
Set 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.
Display the delv help usage output and exit.
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 delv to time out. When it is
necessary to examine invalid data to debug a DNSSEC problem, use dig
Enables memory usage debugging.
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.
Sets the query name to name. While the query name can be specified
without using the -q, 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).
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 type or class when
they are ambiguous. it is sometimes necessary to disambiguate names
The default query type is "A", unless the -x option is supplied to
indicate a reverse lookup, in which case it is "PTR".
Print the delv version and exit.
Performs a reverse lookup, mapping an addresses 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
22.214.171.124.in-addr.arpa and sets the query type to PTR. IPv6
addresses are looked up using nibble format under the IP6.ARPA
Forces delv to only use IPv4.
Forces delv to only use IPv6.
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:
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 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 delv can then validate internally and report
the errors in detail.
Controls whether to display the CLASS when printing a record. The
default is to display the CLASS.
Controls whether to display the TTL when printing a record. The
default is to display the TTL.
Toggle 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: this includes 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 will product the same output (but will affect other logging
categories as well).
Toggle 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 the
"packets" module of the "resolver" logging category. Setting the
systemwide debug level to 10 using the -d option will produce the
same output (but will affect other logging categories as well).
Toggle 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 the
"validator" module of the "dnssec" logging category. Setting the
systemwide debug level to 3 using the -d option will produce the same
output (but will affect other logging categories as well).
Provide a terse answer. The default is to print the answer in a
Toggle the display of comment lines in the output. The default is to
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.
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 ]".
Controls whether to display the trust level when printing a record.
The default is to display the trust level.
Split 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
Set or clear the display options +[no]comments, +[no]rrcomments, and
+[no]trust as a group.
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 delv output.
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 whether to validate them. DNSSEC
records are always requested, and validation will always occur unless
suppressed by the use of -i or +noroot and +nodlv.
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 -a must be used to specify a file containing the key.
Indicates whether to perform DNSSEC lookaside validation, and if so,
specifies the name of the DLV trust anchor. The default is to perform
lookaside validation using a trust anchor of "dlv.isc.org", for which
there is a built-in key. If specifying a different name, then -a must
be used to specify a file containing the DLV key.
The delv command does not use the host name and address resolution or the
DNS query routing mechanisms used by other processes running on macOS.
The results of name or address queries printed by delv may differ from
those found by other processes that use the macOS native name and address
resolution mechanisms. The results of DNS queries may also differ from
queries that use the macOS DNS routing library.
dig(1), named(8), RFC4034, RFC4035, RFC4431, RFC5074, RFC5155.
Internet Systems Consortium, Inc.
Copyright © 2014-2016 Internet Systems Consortium, Inc. ("ISC")
ISC 2018-05-25 DELV(1)