Several How to’s describe operational practices with DNSSEC:
Below, frequently used commands are described:
As automation is not very widespread, DS publication often needs to occur manually as follows:
pdnsutil zone show (pdnsutil show-zone prior to version 5.0)
to display DS and DNSKEY parameters,Some parents accept DS format, while some accept DNSKEY (and use it to derive DS records).
An increasing number of registries support automatic DNSSEC bootstrapping. This requires publication of CDS and/or CDNSKEY records in your zone, which parents can ingest to compute DS records from them. This works for both DS initialization (bootstrapping) and DS updates (rollovers).
CDS/CDNSKEY record publication can be enabled using
pdnsutil zone set-publish-cds or pdnsutil zone set-publish-cdnskey.
For bootstrapping, this method lacks authentication (there is no preexisting chain of trust). Some registries work around this by observing CDS/CDNSKEY records for a few days before acting on them; however, that is not really a replacement for authentication. An authentication method is described below.
The above issue is addressed by “authenticated bootstrapping”, which uses special signaling records with an existing chain of trust so that slow sanity checks can be skipped.
PowerDNS can generate these records automatically. If enabled, it is in effect server-wide, for all zones that have CDS/CDNSKEY records.
To enable, a signaling zone needs to be configured. Assuming you have a
nameserver that appears as ns1.example.net in delegations, you can
enable authenticated bootstrapping as follows:
Make sure that the nameserver ns1.example.net itself is in a secure
zone (with DS records);
Run
nshost=ns1.example.net
pdnsutil zone create _signal.$nshost $nshost # create NS record too
pdnsutil zone set-signaling _signal.$nshost
You can do this on ns1.example.net directly, or on another instance
serving the same zones. This is useful when not all instances are
PowerDNS. (Make sure to adjust NS records accordingly.)
Delegate the signaling zone (_signal.ns1.example.net) to this
PowerDNS instance, and publish DS records for the delegation.
The above steps need to be repeated for each NS hostname used by the domain(s) that you want to bootstrap (such as ``ns2.example.org`` etc.).
Note: A nameserver can’t bootstrap its own parent. (The above example
won’t work to bootstrap example.net; see step 1.) If no other zones
are served under that hostname, you can skip creating its signaling zone.
pdnsutil zone set-signaling _signal.$nshost is equivalent to securing
the zone, enabling NSEC3 narrow mode, and setting the SIGNALING-ZONE
metadata, which will make the zone behave as an RFC 9615 signaling zone.
pdnsutil zone dnssec-disable ZONE
or, prior to version 5.0:
pdnsutil disable-dnssec ZONE
Warning
Going insecure with a zone that has a DS record in the parent zone will make the zone BOGUS. Make sure the parent zone removes the DS record before going insecure.
As stated earlier, PowerDNS uses NSEC by default. If you want to use NSEC3 instead, issue:
pdnsutil zone set-nsec3 ZONE [PARAMETERS] ['narrow']
e.g.
pdnsutil zone set-nsec3 example.net '1 0 0 -'
or, prior to version 5.0:
pdnsutil set-nsec3 example.net '1 0 0 -'
The quoted part is the content of the NSEC3PARAM records, as defined in RFC 5155, in order:
1 (SHA1)1 for NSEC3 Opt-out, this best
set as 0- to use no saltOptionally, NSEC3 can be set to ‘narrow’ mode. For more information refer to (Hashed) Denial of Existence.
To convert a zone from NSEC3 to NSEC operations, run:
pdnsutil zone unset-nsec3 ZONE
or, prior to version 5.0:
pdnsutil unset-nsec3 ZONE
Warning
Don’t change from NSEC to NSEC3 (or the other way around) for zones with algorithm 5 (RSASHA1), 6 (DSA-NSEC3-SHA1) or 7 (RSASHA1-NSEC3-SHA1).
As RRSIGs can expire, secondary servers need to know when to re-transfer the zone. In most implementations (BIND, NSD), this is done by re-signing the full zone outside of the nameserver, increasing the SOA serial and serving the new zone on the primary.
With PowerDNS in Live-signing mode, the SOA serial is not increased by default when the RRSIG dates are rolled.
For zones that use Native replication replication PowerDNS will serve valid RRSIGs on all servers.
For primary zones (where replication happens by means of AXFR), PowerDNS secondaries will automatically re-transfer the zone when it notices the RRSIGs have changed, even when the SOA serial is not increased. This ensures the zone never serves old signatures.
If your DNS setup uses non-PowerDNS secondaries, the secondaries need to know when the signatures have been updated. This can be accomplished by setting the SOA-EDIT metadata for DNSSEC signed zones. This value controls how the value of the SOA serial is modified by PowerDNS.
Note
The SOA serial in the datastore will be untouched, SOA-EDIT is applied to DNS answers with the SOA record.
The default-soa-edit or default-soa-edit-signed configuration options can instead be set to ensure SOA-EDIT is set for every zone.
The ‘inception’ refers to the time that the RRSIGs got updated in live-signing mode. This happens every week (see Signatures). The inception time does not depend on local timezone, but some modes below will use localtime for representation.
Increments the serial with the number of weeks since the UNIX epoch. This should work in every setup; but the result won’t look like YYYYMMDDSS anymore.
For example: a serial of 12345678 will become 12348079 on Wednesday 13th of January 2016 (2401 weeks after the epoch).
Sets the new SOA serial number to the maximum of the old SOA serial number, and age in seconds of the last inception. This requires your backend zone to use the number of seconds since the UNIX epoch as SOA serial. The result is still the age in seconds of the last change to the zone, either by operator changes to the zone or the ‘addition’ of new RRSIGs.
As an example, a serial of 12345678 becomes 1452124800 on Wednesday 13th of January 2016.
Uses the YYYYMMDDSS format for SOA serial numbers. The “inception day” is determined using localtime to get the start of the current signing week (usually Sunday).
Important Notes: - Avoid using SS=00 in backend zones, as it may prevent proper zone transfers (AXFR/IXFR) to secondaries. - Serial overflow can occur if more than 99 updates are made in a single day. - This logic is not safe for zones with non-PowerDNS secondaries, as updates may not be detected reliably.
For full safety with non-PowerDNS secondaries, consider using SOA-EDIT=DEFAULT or managing serials explicitly.
Example:
Assume today is 2025-07-10 (Thursday) and the backend SOA serial is:
2025070901 becomes 2025070902 (still within the 3-day inception window)2025070800 becomes 2025070801 (within the window, SS < 99)2025070701 remains unchanged (outside the window)Sets the SOA serial to the number of seconds since the epoch.
Warning
Don’t combine this with AXFR - the secondaries would keep refreshing all the time. If you need fast updates, sync the backend databases directly with incremental updates (or use the same database server on the secondaries)
Ignore default-soa-edit and/or default-soa-edit-signed settings.
During typical PowerDNS operation, the private part of the signing keys are ‘online’, which can be compared to operating an HTTPS server, where the private key is available on the webserver for cryptographic purposes.
In some settings, having such (private) keying material available online is considered undesirable. In this case, consider running in pre-signed mode.
A slightly more complex approach is running a hidden primary in simple online signing mode, but on a highly secured system unreachable for the public. Internet-connected secondaries can then transfer the zones pre-signed from this primary over a secure private network. This topology offers substantial security benefits with regards to key material while maintaining ease of daily operation by PowerDNS’s features in online mode.
See also Pre-signed records.
DNSSEC has a performance impact, mostly measured in terms of additional memory used for the signature caches. In addition, on startup or AXFR-serving, a lot of signing needs to happen.
Most best practices are documented in RFC 6781.
In zones signed by PowerDNS (so non-presigned zones), some TTL values need to be filled in by PowerDNS. The TTL of RRSIG record sets is the TTL of the covered RRset. For CDS, CDNSKEY, DNSKEY, NSEC, NSEC3 and NSEC3PARAM, we use the SOA minimum (the last number in the SOA record). Except for CDS/CDNSKEY/DNSKEY, these TTLs are chosen because RFC 4034 demands it so.
If you want a ‘normal’ TTL (3600, 86400, etc.) for your DNSKEY but a low TTL on negative answers, set your SOA minimum TTL to the high number, and set the TTL on the SOA record itself to the low TTL you want for negative answers. Note that the NSEC/NSEC3 records proving those negatives will get the high TTL in that case, and this may affect subsequent resolution in resolvers that do aggressive NSEC caching (RFC 8198).
Note
NSEC/NSEC3 records get the negative TTL (which is the lowest of the SOA TTL and the SOA minimum), which means their TTL matches that of a response such as NXDOMAIN. This conforms to RFC 9077.
Prior to version 4.3.0, the behaviour was based on language in RFC 4034 and RFC 5155 about the NSEC/NSEC3 TTL.