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, us-
ing 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, 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 forward-
ing.
By default, responses are validated using built-in DNSSEC trust anchor
for the root zone ("."). Records returned by delv are either fully val-
idated 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 ad-
dresses 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).
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/re-
solv.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).
name is the domain name to be looked up.
type indicates what type of query is required MDASH ANY, A, MX, etc.
type can be any valid query type. If no type argument is sup-
plied, delv will perform a lookup for an A record.
OPTIONS
-a anchor-file
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 alter-
nate key name can be specified using the +root=NAME options.
Note: When reading the trust anchor file, delv treat trust-an-
chors 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 will not consult the man-
aged-keys database maintained by named. This means that if ei-
ther of the keys in /etc/bind.keys is revoked and rolled over,
it will be necessary to update /etc/bind.keys to use DNSSEC val-
idation in delv.
-b address
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
Sets the query class for the requested data. Currently, only
class "IN" is supported in delv and any other value is ignored.
-d level
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.
-h Display the delv help usage output and exit.
-i 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 +cd.)
-m Enables memory usage debugging.
-p port#
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.
-q name
Sets the query name to name. While the query name can be speci-
fied without using the -q, it is sometimes necessary to disam-
biguate 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
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 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 Print the delv version and exit.
-x addr
Performs a reverse lookup, mapping an addresses to a name. addr
is an IPv4 address in dotted-decimal notation, or a colon-delim-
ited 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 Forces delv to only use IPv4.
-6 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 +key-
word=value. The query options are:
+[no]cdflag
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.
+[no]class
Controls whether to display the CLASS when printing a record.
The default is to display the CLASS.
+[no]ttl
Controls whether to display the TTL when printing a record. The
default is to display the TTL.
+[no]rtrace
Toggle resolver fetch logging. This reports the name and type of
each query sent by delv in the process of carrying out the reso-
lution and validation process: this includes including the orig-
inal 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 "re-
solver" logging category. Setting the systemwide debug level to
1 using the -d option will product the same output (but will af-
fect other logging categories as well).
+[no]mtrace
Toggle message logging. This produces a detailed dump of the re-
sponses received by delv in the process of carrying out the res-
olution 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 will produce
the same output (but will affect other logging categories as
well).
+[no]vtrace
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 "val-
idator" 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).
+[no]short
Provide a terse answer. The default is to print the answer in a
verbose form.
+[no]comments
Toggle the display of comment lines in the output. The default
is to print comments.
+[no]rrcomments
Toggle the display of per-record comments in the output (for ex-
ample, human-readable key information about DNSKEY records). The
default is to print per-record comments.
+[no]crypto
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 ]".
+[no]trust
Controls whether to display the trust level when printing a
record. The default is to display the trust level.
+[no]split[=W]
Split long hex- or base64-formatted fields in resource records
into chunks of W characters (where W is rounded up to the near-
est 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
Set or clear the display options +[no]comments, +[no]rrcomments,
and +[no]trust as a group.
+[no]multiline
Print long records (such as RRSIG, DNSKEY, and SOA records) in a
verbose multi-line format with human-readable comments. The de-
fault is to print each record on a single line, to facilitate
machine parsing of the delv output.
+[no]dnssec
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.
+[no]root[=ROOT]
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
Controls whether to use TCP when sending queries. The default is
to use UDP unless a truncated response has been received.
+[no]unknownformat
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.
+[no]yaml
Print 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
2020, Internet Systems Consortium
9.16.8-Debian 2020-10-13 DELV(1)