{ "mode": "man", "parameter": "DELV", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/DELV/1/json", "generated": "2026-06-15T14:38:46Z", "synopsis": "delv [@server] [ [-4] | [-6] ] [-a anchor-file] [-b address] [-c class] [-d level] [-i] [-m]\n[-p port#] [-q name] [-t type] [-x addr] [name] [type] [class] [queryopt...]\ndelv [-h]\ndelv [-v]\ndelv [queryopt...] [query...]", "sections": { "NAME": { "content": "delv - DNS lookup and validation utility\n", "subsections": [] }, "SYNOPSIS": { "content": "delv [@server] [ [-4] | [-6] ] [-a anchor-file] [-b address] [-c class] [-d level] [-i] [-m]\n[-p port#] [-q name] [-t type] [-x addr] [name] [type] [class] [queryopt...]\n\ndelv [-h]\n\ndelv [-v]\n\ndelv [queryopt...] [query...]\n", "subsections": [] }, "DESCRIPTION": { "content": "delv is a tool for sending DNS queries and validating the results, using the same internal\nresolver and validator logic as named.\n\ndelv sends to a specified name server all queries needed to fetch and validate the requested\ndata; this includes the original requested query, subsequent queries to follow CNAME or DNAME\nchains, queries for DNSKEY, and DS records to establish a chain of trust for DNSSEC valida‐\ntion. It does not perform iterative resolution, but simulates the behavior of a name server\nconfigured for DNSSEC validating and forwarding.\n\nBy default, responses are validated using the built-in DNSSEC trust anchor for the root zone\n(\".\"). Records returned by delv are either fully validated or were not signed. If validation\nfails, an explanation of the failure is included in the output; the validation process can be\ntraced in detail. Because delv does not rely on an external server to carry out validation,\nit can be used to check the validity of DNS responses in environments where local name\nservers may not be trustworthy.\n\nUnless it is told to query a specific name server, delv tries each of the servers listed in\n/etc/resolv.conf. If no usable server addresses are found, delv sends queries to the local‐\nhost addresses (127.0.0.1 for IPv4, ::1 for IPv6).\n\nWhen no command-line arguments or options are given, delv performs an NS query for \".\" (the\nroot zone).\n", "subsections": [] }, "SIMPLE USAGE": { "content": "A typical invocation of delv looks like:\n\ndelv @server name type\n\nwhere:\n\nserver is the name or IP address of the name server to query. This can be an IPv4 address in\ndotted-decimal notation or an IPv6 address in colon-delimited notation. When the sup‐\nplied server argument is a hostname, delv resolves that name before querying that name\nserver (note, however, that this initial lookup is not validated by DNSSEC).\n\nIf no server argument is provided, delv consults /etc/resolv.conf; if an address is\nfound there, it queries the name server at that address. If either of the -4 or -6 op‐\ntions is in use, then only addresses for the corresponding transport are tried. If no\nusable addresses are found, delv sends queries to the localhost addresses (127.0.0.1\nfor IPv4, ::1 for IPv6).\n\nname is the domain name to be looked up.\n\ntype indicates what type of query is required - ANY, A, MX, etc. type can be any valid\nquery type. If no type argument is supplied, delv performs a lookup for an A record.\n", "subsections": [] }, "OPTIONS": { "content": "", "subsections": [ { "name": "-a anchor-file", "content": "This option specifies a file from which to read DNSSEC trust anchors. The default is\n/etc/bind/bind.keys, which is included with BIND 9 and contains one or more trust an‐\nchors for the root zone (\".\").\n\nKeys that do not match the root zone name are ignored. An alternate key name can be\nspecified using the +root option.\n\nNote: When reading the trust anchor file, delv treats trust-anchors, initial-key, and\nstatic-key identically. That is, for a managed key, it is the initial key that is\ntrusted; RFC 5011 key management is not supported. delv does not consult the man‐\naged-keys database maintained by named, which means that if either of the keys in\n/etc/bind/bind.keys is revoked and rolled over, /etc/bind/bind.keys must be updated to\nuse DNSSEC validation in delv.\n", "flag": "-a" }, { "name": "-b address", "content": "This option sets the source IP address of the query to address. This must be a valid\naddress on one of the host's network interfaces, or 0.0.0.0, or ::. An optional source\nport may be specified by appending #\n", "flag": "-b" }, { "name": "-c class", "content": "This option sets the query class for the requested data. Currently, only class \"IN\" is\nsupported in delv and any other value is ignored.\n", "flag": "-c" }, { "name": "-d level", "content": "This option sets the systemwide debug level to level. The allowed range is from 0 to\n99. The default is 0 (no debugging). Debugging traces from delv become more verbose as\nthe debug level increases. See the +mtrace, +rtrace, and +vtrace options below for ad‐\nditional debugging details.\n", "flag": "-d" }, { "name": "-h", "content": "", "flag": "-h" }, { "name": "-i", "content": "ever, that this does not set the CD bit on upstream queries. If the server being\nqueried is performing DNSSEC validation, then it does not return invalid data; this\ncan cause delv to time out. When it is necessary to examine invalid data to debug a\nDNSSEC problem, use dig +cd.)\n", "flag": "-i" }, { "name": "-m", "content": "", "flag": "-m" }, { "name": "-p port#", "content": "This option specifies a destination port to use for queries, instead of the standard\nDNS port number 53. This option is used with a name server that has been configured to\nlisten for queries on a non-standard port number.\n", "flag": "-p" }, { "name": "-q name", "content": "This option sets the query name to name. While the query name can be specified without\nusing the -q option, it is sometimes necessary to disambiguate names from types or\nclasses (for example, when looking up the name \"ns\", which could be misinterpreted as\nthe type NS, or \"ch\", which could be misinterpreted as class CH).\n", "flag": "-q" }, { "name": "-t type", "content": "This option sets the query type to type, which can be any valid query type supported\nin BIND 9 except for zone transfer types AXFR and IXFR. As with -q, this is useful to\ndistinguish query-name types or classes when they are ambiguous. It is sometimes nec‐\nessary to disambiguate names from types.\n\nThe default query type is \"A\", unless the -x option is supplied to indicate a reverse\nlookup, in which case it is \"PTR\".\n", "flag": "-t" }, { "name": "-v", "content": "", "flag": "-v" }, { "name": "-x addr", "content": "This option performs a reverse lookup, mapping an address to a name. addr is an IPv4\naddress in dotted-decimal notation, or a colon-delimited IPv6 address. When -x is\nused, there is no need to provide the name or type arguments; delv automatically per‐\nforms a lookup for a name like 11.12.13.10.in-addr.arpa and sets the query type to\nPTR. IPv6 addresses are looked up using nibble format under the IP6.ARPA domain.\n", "flag": "-x" }, { "name": "-4", "content": "", "flag": "-4" }, { "name": "-6", "content": "", "flag": "-6" } ] }, "QUERY OPTIONS": { "content": "delv provides a number of query options which affect the way results are displayed, and in\nsome cases the way lookups are performed.\n\nEach query option is identified by a keyword preceded by a plus sign (+). Some keywords set\nor reset an option. These may be preceded by the string no to negate the meaning of that key‐\nword. Other keywords assign values to options like the timeout interval. They have the form\n+keyword=value. The query options are:\n", "subsections": [ { "name": "+cdflag, +nocdflag", "content": "This option controls whether to set the CD (checking disabled) bit in queries sent by\ndelv. This may be useful when troubleshooting DNSSEC problems from behind a validating\nresolver. A validating resolver blocks invalid responses, making it difficult to re‐\ntrieve them for analysis. Setting the CD flag on queries causes the resolver to return\ninvalid responses, which delv can then validate internally and report the errors in\ndetail.\n" }, { "name": "+class, +noclass", "content": "This option controls whether to display the CLASS when printing a record. The default\nis to display the CLASS.\n" }, { "name": "+ttl, +nottl", "content": "This option controls whether to display the TTL when printing a record. The default is\nto display the TTL.\n" }, { "name": "+rtrace, +nortrace", "content": "This option toggles resolver fetch logging. This reports the name and type of each\nquery sent by delv in the process of carrying out the resolution and validation\nprocess, including the original query and all subsequent queries to follow CNAMEs and\nto establish a chain of trust for DNSSEC validation.\n\nThis is equivalent to setting the debug level to 1 in the \"resolver\" logging category.\nSetting the systemwide debug level to 1 using the -d option produces the same output,\nbut affects other logging categories as well.\n" }, { "name": "+mtrace, +nomtrace", "content": "This option toggles message logging. This produces a detailed dump of the responses\nreceived by delv in the process of carrying out the resolution and validation process.\n\nThis is equivalent to setting the debug level to 10 for the \"packets\" module of the\n\"resolver\" logging category. Setting the systemwide debug level to 10 using the -d op‐\ntion produces the same output, but affects other logging categories as well.\n" }, { "name": "+vtrace, +novtrace", "content": "This option toggles validation logging. This shows the internal process of the valida‐\ntor as it determines whether an answer is validly signed, unsigned, or invalid.\n\nThis is equivalent to setting the debug level to 3 for the \"validator\" module of the\n\"dnssec\" logging category. Setting the systemwide debug level to 3 using the -d option\nproduces the same output, but affects other logging categories as well.\n" }, { "name": "+short, +noshort", "content": "This option toggles between verbose and terse answers. The default is to print the an‐\nswer in a verbose form.\n" }, { "name": "+comments, +nocomments", "content": "This option toggles the display of comment lines in the output. The default is to\nprint comments.\n" }, { "name": "+rrcomments, +norrcomments", "content": "This option toggles the display of per-record comments in the output (for example, hu‐\nman-readable key information about DNSKEY records). The default is to print per-record\ncomments.\n" }, { "name": "+crypto, +nocrypto", "content": "This option toggles the display of cryptographic fields in DNSSEC records. The con‐\ntents of these fields are unnecessary to debug most DNSSEC validation failures and re‐\nmoving them makes it easier to see the common failures. The default is to display the\nfields. When omitted, they are replaced by the string [omitted] or, in the DNSKEY\ncase, the key ID is displayed as the replacement, e.g. [ key id = value ].\n" }, { "name": "+trust, +notrust", "content": "This option controls whether to display the trust level when printing a record. The\ndefault is to display the trust level.\n" }, { "name": "+split[=W], +nosplit", "content": "This option splits long hex- or base64-formatted fields in resource records into\nchunks of W characters (where W is rounded up to the nearest multiple of 4). +nosplit\nor +split=0 causes fields not to be split at all. The default is 56 characters, or 44\ncharacters when multiline mode is active.\n" }, { "name": "+all, +noall", "content": "This option sets or clears the display options +comments, +rrcomments, and +trust as a\ngroup.\n" }, { "name": "+multiline, +nomultiline", "content": "This option prints long records (such as RRSIG, DNSKEY, and SOA records) in a verbose\nmulti-line format with human-readable comments. The default is to print each record on\na single line, to facilitate machine parsing of the delv output.\n" }, { "name": "+dnssec, +nodnssec", "content": "This option indicates whether to display RRSIG records in the delv output. The de‐\nfault is to do so. Note that (unlike in dig) this does not control whether to request\nDNSSEC records or to validate them. DNSSEC records are always requested, and valida‐\ntion always occurs unless suppressed by the use of -i or +noroot.\n" }, { "name": "+root[=ROOT], +noroot", "content": "This option indicates whether to perform conventional DNSSEC validation, and if so,\nspecifies the name of a trust anchor. The default is to validate using a trust anchor\nof \".\" (the root zone), for which there is a built-in key. If specifying a different\ntrust anchor, then -a must be used to specify a file containing the key.\n" }, { "name": "+tcp, +notcp", "content": "This option controls whether to use TCP when sending queries. The default is to use\nUDP unless a truncated response has been received.\n" }, { "name": "+unknownformat, +nounknownformat", "content": "This option prints all RDATA in unknown RR-type presentation format (RFC 3597). The\ndefault is to print RDATA for known types in the type's presentation format.\n" }, { "name": "+yaml, +noyaml", "content": "This option prints response data in YAML format.\n" } ] }, "FILES": { "content": "", "subsections": [ { "name": "/etc/bind/bind.keys", "content": "" }, { "name": "/etc/resolv.conf", "content": "" } ] }, "SEE ALSO": { "content": "dig(1), named(8), RFC 4034, RFC 4035, RFC 4431, RFC 5074, RFC 5155.\n", "subsections": [] }, "AUTHOR": { "content": "Internet Systems Consortium\n", "subsections": [] }, "COPYRIGHT": { "content": "2026, Internet Systems Consortium\n\n\n\n\n9.18.39-0ubuntu0.22.04.4-Ubuntu 2025-08-13 DELV(1)", "subsections": [] } }, "summary": "delv - DNS lookup and validation utility", "flags": [ { "flag": "-a", "long": null, "arg": null, "description": "This option specifies a file from which to read DNSSEC trust anchors. The default is /etc/bind/bind.keys, which is included with BIND 9 and contains one or more trust an‐ chors 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 man‐ aged-keys database maintained by named, which means that if either of the keys in /etc/bind/bind.keys is revoked and rolled over, /etc/bind/bind.keys must be updated to use DNSSEC validation in delv." }, { "flag": "-b", "long": null, "arg": null, "description": "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 #" }, { "flag": "-c", "long": null, "arg": null, "description": "This option sets the query class for the requested data. Currently, only class \"IN\" is supported in delv and any other value is ignored." }, { "flag": "-d", "long": null, "arg": null, "description": "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 ad‐ ditional debugging details." }, { "flag": "-h", "long": null, "arg": null, "description": "" }, { "flag": "-i", "long": null, "arg": null, "description": "ever, 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.)" }, { "flag": "-m", "long": null, "arg": null, "description": "" }, { "flag": "-p", "long": null, "arg": null, "description": "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." }, { "flag": "-q", "long": null, "arg": null, "description": "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)." }, { "flag": "-t", "long": null, "arg": null, "description": "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 nec‐ essary 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\"." }, { "flag": "-v", "long": null, "arg": null, "description": "" }, { "flag": "-x", "long": null, "arg": null, "description": "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 per‐ forms 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." }, { "flag": "-4", "long": null, "arg": null, "description": "" }, { "flag": "-6", "long": null, "arg": null, "description": "" } ], "examples": [], "see_also": [ { "name": "dig", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/dig/1/json" }, { "name": "named", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/named/8/json" } ] }