Go to main content

man pages section 1M: System Administration Commands

Exit Print View

Updated: July 2017



dnssec-signzone - DNSSEC zone signing tool


dnssec-signzone [-Aaghptz] [-c class] [-d directory] 
     [-e end-time] [-f output-file] [-H iterations] [-I input_format]
     [-i interval] [-k key] [-l domain] [-N soa-serial-format] [-n ncpus]
     [-O output_format] [-o origin] [-r randomdev] [-s start-time]
     [-v level] [-3 salt] zonefile [key]...


The dnssec-signzone utility signs a zone. It generates NSEC and RRSIG records and produces a signed version of the zone. The security status of delegations from the signed zone (that is, whether the child zones are secure or not) is determined by the presence or absence of a keyset file for each child zone.


The following options are supported:


When generating an NSEC3 chain, set the OPTOUT flag on all NSEC3 records and do not generate NSEC3 records for insecure delegations.


Verify all generated signatures.

–c class

Specify the DNS class of the zone.

–d directory

Look for keyset files in directory.

–e end-time

Specify the date and time when the generated RRSIG records expire. As with start-time, an absolute time is indicated in YYYYMMDDHHMMSS notation. A time relative to the start time is indicated with +N, which is N seconds from the start time. A time relative to the current time is indicated with now+N. If no end-time is specified, 30 days from the start time is used as a default.

–f output-file

The name of the output file containing the signed zone. The default is to append .signed to the input file name.


Generate DS records for child zones from keyset files. Existing DS records will be removed.

–H iterations

When generating a NSEC3 chain use the number of interations specified by iterations. The default is 100.


Prints a short summary of the options and arguments to dnssec-signzone().

–I input-format

The format of the input zone file. Possible formats are text (default) and raw. This option is primarily intended for dynamic signed zones so that the dumped zone file in a non-text format containing updates can be signed directly. The use of this option serves no purpose for non-dynamic zones.

–i interval

Specify the cycle interval as an offset from the current time (in seconds). When a previously signed zone is passed as input, records could be resigned. If an RRSIG record expires after the cycle interval, it is retained. Otherwise, it is considered to be expiring soon and will be replaced.

The default cycle interval is one quarter of the difference between the signature end and start times. If neither end-time or start-time are specified, dnssec-signzone generates signatures that are valid for 30 days, with a cycle interval of 7.5 days. Any existing RRSIG records due to expire in less than 7.5 days would be replaced.

–j jitter

When signing a zone with a fixed signature lifetime, all RRSIG records issued at the time of signing expire simultaneously. If the zone is incrementally signed, that is, a previously-signed zone is passed as input to the signer, all expired signatures have to be regenerated at about the same time. The jitter option specifies a jitter window that will be used to randomize the signature-expire time, thus spreading incremental signature regeneration over time.

Signature lifetime jitter also benefits, to some extent, validators and servers by spreading out cache expiration. That is, if large numbers of RRSIGs from all caches do not expire at the same time, there will be less congestion than if all validators needed to refetch at almost the same time.

–k key

Treat specified key as a key-signing key, ignoring any key flags. This option can be specified multiple times.

–l domain

Generate a DLV set in addition to the key (DNSKEY) and DS sets. The domain is appended to the name of the records.

–N soa-serial-format

The SOA serial number format of the signed zone. Possible formats are keep (default), increment and unixtime, described as follows.


Do not modify the SOA serial number.


Increment the SOA serial number using RFC 1982 arithmetic.


Set the SOA serial number to the number of seconds since epoch.

–n nthreads

Specifies the number of threads to use. By default, one thread is started for each detected CPU.

–O output_format

The format of the output file containing the signed zone. Possible formats are text (default) and raw.

–o origin

Specify the zone origin. If not specified, the name of the zone file is assumed to be the origin.


Use pseudo-random data when signing the zone. This is faster, but less secure, than using real random data. This option may be useful when signing large zones or when the entropy source is limited.

–r randomdev

Specifies the source of randomness. If the operating system does not provide a /dev/random or equivalent device, the default source of randomness is keyboard input. randomdev specifies the name of a character device or file containing random data to be used instead of the default /dev/random. The special value keyboard indicates that keyboard input should be used.

–s start-time

Specify the date and time when the generated RRSIG records become valid. This can be either an absolute or relative time. An absolute start time is indicated by a number in YYYYMMDDHHMMSS notation; 20000530144500 denotes 14:45:00 UTC on May 30th, 2000. A relative start time is indicated by +N, which is N seconds from the current time. If no start-time is specified, the current time minus one hour (to allow for clock skew) is used.


Print statistics at completion.

–v level

Set the debugging level.


Ignore KSK flag on key when determining what to sign.

–3 salt

Generate a NSEC3 chain with the specified hex-encoded salt. A dash (-) can be used to indicate that no salt is to be used when generating the NSEC3 chain.


The following operands are supported:


The file containing the zone to be signed.


Specify which keys should be used to sign the zone. If no keys are specified, then the zone will be examined for DNSKEY records at the zone apex. If these are found and there are matching private keys in the current directory, these will be used for signing.


Example 1 Signing a Zone with a DSA Key

The following command signs the example.com zone with the DSA key generated in the example in the dnssec-keygen(1M) manual page (Kexample.com.+003+17247). The zone's keys must be in the master file (db.example.com). This invocation looks for keyset files in the current directory, so that DS records can be generated from them (–g).

% dnssec-signzone -g -o example.com db.example.com \

In the above example, dnssec-signzone creates the file db.example.com.signed. This file should be referenced in a zone statement in a named.conf file.

Example 2 Re-signing a Previously Signed Zone

The following commands re-sign a previously signed zone with default parameters. The private keys are assumed to be in the current directory.

% cp db.example.com.signed db.example.com
% dnssec-signzone -o example.com db.example.com \


See attributes(5) for descriptions of the following attributes:

Interface Stability

See Also

dnssec-keygen(1M), attributes(5)

RFC 4033

See the BIND 9 Administrator's Reference Manual. As of the date of publication of this man page, this document is available at https://kb.isc.org/article/AA-01031https://kb.isc.org/article/AA-01031.