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KNOT.CONF(5) Knot DNS KNOT.CONF(5)

NAME
knot.conf - Knot DNS configuration file

DESCRIPTION
Configuration files for Knot DNS use simplified YAML format. Simplified
means that not all of the features are supported.

For the description of configuration items, we have to declare a meaning of
the following symbols:

* INT a Integer

* STR a Textual string

* HEXSTR a Hexadecimal string (with 0x prefix)

* BOOL a Boolean value (on/off or true/false)

* TIME a Number of seconds, an integer with a possible time multiplier suf-
fix (s ~ 1, m ~ 60, h ~ 3600, d ~ 24 * 3600, w ~ 7 * 24 * 3600, M ~ 30 *
24 * 3600, y ~ 365 * 24 * 3600)

* SIZE a Number of bytes, an integer with a possible size multiplier suffix
(B ~ 1, K ~ 1024, M ~ 1024^2 or G ~ 1024^3)

* BASE64 a Base64 encoded string

* ADDR a IPv4 or IPv6 address

* DNAME a Domain name

* ... a Multi-valued item, order of the values is preserved

* [ ] a Optional value

* | a Choice

The configuration consists of several fixed sections and optional module
sections. There are 18 fixed sections (module, server, xdp, control, log,
statistics, database, keystore, key, remote, remotes, acl, submission,
dnskey-sync, policy, external`, template, zone). Module sections are pre-
fixed with the mod- prefix (e.g. mod-stats).

Most of the sections (e.g. zone) are sequences of settings blocks. Each
settings block begins with a unique identifier, which can be used as a ref-
erence from other sections (such an identifier must be defined in advance).

A multi-valued item can be specified either as a YAML sequence:

address: [10.0.0.1, 10.0.0.2]

or as more single-valued items each on an extra line:

address: 10.0.0.1
address: 10.0.0.2

If an item value contains spaces or other special characters, it is neces-
sary to enclose such a value within double quotes " ".

If not specified otherwise, an item representing a file or a directory path
may be defined either as an absolute path (starting with /), or a path rel-
ative to the same directory as the default value of the item.

COMMENTS
A comment begins with a # character and is ignored during processing. Also
each configuration section or sequence block allows a permanent comment us-
ing the comment item which is stored in the server beside the configura-
tion.

INCLUDING CONFIGURATION
Another configuration file or files, matching a pattern, can be included at
the top level in the current file.

include: STR

include
A path or a matching pattern specifying one or more files that are included
at the place of the include option position in the configuration. If the
path is not absolute, then it is considered to be relative to the current
file. The pattern can be an arbitrary string meeting POSIX glob require-
ments, e.g. dir/*.conf. Matching files are processed in sorted order.

Default: not set

CLEARING CONFIGURATION SECTIONS
It's possible to clear specified configuration sections at given phases of
the configuration parsing.

clear: STR

clear
A matching pattern specifying configuration sections that are cleared when
this item is parsed. This allows overriding of existing configuration in
the configuration database when including a configuration file or ensures
that some configuration wasn't specified in previous includes.

NOTE:
For the pattern matching the POSIX function fnmatch() is used. On Linux,
the GNU extension FNM_EXTMATCH is enabled, which allows extended pattern
matching. Examples:

* clear: zone a Clears the zone section.

* clear: mod-* a Clears all module sections.

* clear: "[!z]*" a Clears all sections not beginning with letter z.

* clear: !(zone) a (GNU only) Clears all sections except the zone one.

* clear: @(zone|template) a (GNU only) Clears the zone and template sec-
tions.

Default: not set

MODULE SECTION
Dynamic modules loading configuration.

NOTE:
If configured with non-empty --with-moduledir=path parameter, all shared
modules in this directory will be automatically loaded.

module:
- id: STR
file: STR

id
A module identifier in the form of the mod- prefix and module name suffix.

file
A path to a shared library file with the module implementation.

WARNING:
If the path is not absolute, the library is searched in the set of sys-
tem directories. See man dlopen for more details.

Default: ${libdir}/knot/modules-${version}/module_name.so (or ${path}/mod-
ule_name.so if configured with --with-moduledir=path)

SERVER SECTION
General options related to the server.

server:
identity: [STR]
version: [STR]
nsid: [STR|HEXSTR]
rundir: STR
user: STR[:STR]
pidfile: STR
udp-workers: INT
tcp-workers: INT
background-workers: INT
async-start: BOOL
tcp-idle-timeout: TIME
tcp-io-timeout: INT
tcp-remote-io-timeout: INT
tcp-max-clients: INT
tcp-reuseport: BOOL
tcp-fastopen: BOOL
quic-max-clients: INT
quic-outbuf-max-size: SIZE
quic-idle-close-timeout: TIME
remote-pool-limit: INT
remote-pool-timeout: TIME
remote-retry-delay: INT
socket-affinity: BOOL
udp-max-payload: SIZE
udp-max-payload-ipv4: SIZE
udp-max-payload-ipv6: SIZE
key-file: STR
cert-file: STR
ca-file: STR ...
edns-client-subnet: BOOL
answer-rotation: BOOL
automatic-acl: BOOL
proxy-allowlist: ADDR[/INT] | ADDR-ADDR ...
dbus-event: none | running | zone-updated | external-verify | ksk-submission | dnssec-invalid ...
dbus-init-delay: TIME
listen: ADDR[%STR][@INT] | STR ...
listen-quic: ADDR[%STR][@INT] ...
listen-tls: ADDR[%STR][@INT] ...

CAUTION:
When you change configuration parameters dynamically or via configura-
tion file reload, some parameters in the Server section require restart-
ing the Knot server so that the changes take effect. See below for the
details.

identity
An identity of the server returned in the response to the query for TXT
record id.server. or hostname.bind. in the CHAOS class (RFC 4892). Set to
an empty value to disable.

Default: FQDN hostname

version
A version of the server software returned in the response to the query for
TXT record version.server. or version.bind. in the CHAOS class (RFC 4892).
Set to an empty value to disable.

Default: server version

nsid
A DNS name server identifier (RFC 5001). Set to an empty value to disable.

Default: FQDN hostname at the moment of the daemon start

rundir
A path for storing run-time data (PID file, unix sockets, etc.). A non-ab-
solute path is relative to the knotd startup directory.

Depending on the usage of this parameter, its change may require restart of
the Knot server to take effect.

Default: ${localstatedir}/run/knot (configured with --with-rundir=path)

user
A system user with an optional system group (user:group) under which the
server is run after starting and binding to interfaces. Linux capabilities
are employed if supported.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: root:root

pidfile
A PID file location.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: rundir/knot.pid

udp-workers
A number of UDP workers (threads) used to process incoming queries over
UDP.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: equal to the number of online CPUs

tcp-workers
A number of TCP workers (threads) used to process incoming queries over
TCP.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: equal to the number of online CPUs, default value is at least 10

background-workers
A number of workers (threads) used to execute background operations (zone
loading, zone updates, etc.).

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: equal to the number of online CPUs, default value is at most 10

async-start
If enabled, server doesn't wait for the zones to be loaded and starts re-
sponding immediately with SERVFAIL answers until the zone loads.

Default: off

tcp-idle-timeout
Maximum idle time (in seconds) between requests on an inbound TCP connec-
tion. It means if there is no activity on an inbound TCP connection during
this limit, the connection is closed by the server.

Minimum: 1

Default: 10

tcp-io-timeout
Maximum time (in milliseconds) to receive or send one DNS message over an
inbound TCP connection. It means this limit applies to normal DNS queries
and replies, incoming DDNS, and outgoing zone transfers. The timeout is
measured since some data is already available for processing. Set to 0 for
infinity.

Default: 500 (milliseconds)

CAUTION:
In order to reduce the risk of Slow Loris attacks, it's recommended set-
ting this limit as low as possible on public servers.

tcp-remote-io-timeout
Maximum time (in milliseconds) to receive or send one DNS message over an
outbound TCP/QUIC/TLS connection which has already been established to a
configured remote server. It means this limit applies to incoming zone
transfers, sending NOTIFY, DDNS forwarding, and DS check or push. This
timeout includes the time needed for a network round-trip and for a query
processing by the remote. Set to 0 for infinity.

Default: 5000 (milliseconds)

tcp-reuseport
If enabled, each TCP worker listens on its own socket and the OS kernel
socket load balancing is employed using SO_REUSEPORT (or SO_REUSEPORT_LB on
FreeBSD). Due to the lack of one shared socket, the server can offer higher
response rate processing over TCP. However, in the case of time-consuming
requests (e.g. zone transfers of a TLD zone), enabled reuseport may result
in delayed or not being responded client requests. So it is advisable to
use this option on secondary servers.

NOTE:
This option is ignored for UNIX sockets.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: off

tcp-fastopen
If enabled, use TCP Fast Open for outbound TCP communication (client side):
incoming zone transfers, sending NOTIFY, and DDNS forwarding. This mode
simplifies TCP handshake and can result in better networking performance.
TCP Fast Open for inbound TCP communication (server side) isn't affected by
this configuration as it's enabled automatically if supported by OS.

NOTE:
The TCP Fast Open support must also be enabled on the OS level:

* Linux/macOS: ensure kernel parameter net.ipv4.tcp_fastopen is 2 or 3
for server side, and 1 or 3 for client side.

* FreeBSD: ensure kernel parameter net.inet.tcp.fastopen.server_enable
is 1 for server side, and net.inet.tcp.fastopen.client_enable is 1 for
client side.

Default: off

quic-max-clients
A maximum number of QUIC clients connected in parallel.

See also quic.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Minimum: 128

Default: 10000 (ten thousand)

quic-outbuf-max-size
Maximum cumulative size of memory used for buffers of unACKed sent mes-
sages. This limit is per one UDP worker.

NOTE:
Temporarily, more memory can be occupied by the buffers until some con-
nections are cleared to free some memory and enforce the limit.

Set low if little memory is available (together with quic-max-clients
since QUIC connections are memory-heavy). Set to high value if outgoing
zone transfers of big zone over QUIC are expected.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Minimum: 1M (1 MiB)

Default: 100M (100 MiB)

quic-idle-close-timeout
Time in seconds, after which any idle QUIC connection is gracefully closed.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Minimum: 1

Default: 4

remote-pool-limit
If nonzero, the server will keep up to this number of outgoing TCP connec-
tions open for later use. This is an optimization to avoid frequent opening
of TCP connections to the same remote.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: 0

remote-pool-timeout
The timeout in seconds after which the unused kept-open outgoing TCP con-
nections to remote servers are closed.

Default: 5

remote-retry-delay
When a connection attempt times out to some remote address, this informa-
tion will be kept for this specified time (in milliseconds) and other con-
nections to the same address won't be attempted. This prevents repetitive
waiting for timeout on an unreachable remote.

Default: 0

socket-affinity
If enabled and if SO_REUSEPORT is available on Linux, all configured net-
work sockets are bound to UDP and TCP workers in order to increase the net-
working performance. This mode isn't recommended for setups where the num-
ber of network card queues is lower than the number of UDP or TCP workers.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: off

tcp-max-clients
A maximum number of TCP clients connected in parallel, set this below the
file descriptor limit to avoid resource exhaustion.

NOTE:
It is advisable to adjust the maximum number of open files per process
in your operating system configuration.

Default: one half of the file descriptor limit for the server process

udp-max-payload
Maximum EDNS0 UDP payload size default for both IPv4 and IPv6.

Default: 1232

udp-max-payload-ipv4
Maximum EDNS0 UDP payload size for IPv4.

Default: 1232

udp-max-payload-ipv6
Maximum EDNS0 UDP payload size for IPv6.

Default: 1232

key-file
Path to a server key PEM file which is used for DNS over QUIC/TLS communi-
cation. A non-absolute path of a user specified key file is relative to
the /usr/local/etc/knot directory.

Default: auto-generated key

cert-file
Path to a server certificate PEM file which is used for DNS over QUIC/TLS
communication. A non-absolute path is relative to the /usr/local/etc/knot
directory.

Default: one-time in-memory certificate

ca-file
Specifies one or more paths to load trusted Certificate Authorities (CAs)
from. An empty string ("") means the systemas default trusted CAs. The
loaded CAs are used for remote certificate validation (cert-hostname,
cert-hostname, and zone-db-cert-hostname).

Default: not set

edns-client-subnet
Enable or disable EDNS Client Subnet support. If enabled, responses to
queries containing the EDNS Client Subnet option always contain a valid
EDNS Client Subnet option according to RFC 7871.

Default: off

answer-rotation
Enable or disable sorted-rrset rotation in the answer section of normal
replies. The rotation shift is simply determined by a query ID.

Default: off

automatic-acl
If enabled, automatic ACL setting of configured remotes is considered when
evaluating authorized operations.

Default: off

proxy-allowlist
An ordered list of IP addresses, network subnets, or network ranges which
are allowed as a source address of proxied DNS traffic over UDP. The sup-
ported proxy protocol is haproxy PROXY v2.

NOTE:
TCP is not supported.

Default: not set

dbus-event
Specification of server or zone states which emit a D-Bus signal on the
system bus. The bus name is cz.nic.knotd, the object path is /cz/nic/knotd,
and the interface name is cz.nic.knotd.events.

Possible values:

* none a No signal is emitted.

* running a Two signals may be emitted:

* started a Emitted when the server is started and all configured zones
(including catalog zones and their members) are loaded or successfully
bootstrapped.

* stopped a Emitted when the server shutdown sequence is initiated.

* zone-updated a Two signals may be emitted:

* zone_updated a Emitted when a zone has been successfully updated. Pa-
rameters: zone name and zone SOA serial.

* zone_not_updated a Emitted when a zone has not been successfully up-
dated. Parameters: zone name.

* external-verify a The signal external_verify is emitted when a zone is
awaiting external validation before applying changes. Parameters: zone
name and new zone SOA serial.

* keys-updated a The signal keys_updated is emitted when a DNSSEC key set
is updated. Parameters: zone name.

* ksk-submission a The signal zone_ksk_submission is emitted if a ready KSK
is present when the zone is signed. Parameters: zone name, KSK keytag,
and KSK KASP id.

* dnssec-invalid a The signal zone_dnssec_invalid is emitted when DNSSEC
validation fails or when ZONEMD verification fails. Parameters: zone
name and remaining seconds until an RRSIG expires.

NOTE:
This function requires systemd version at least 221 or libdbus.

TIP:
A few sample script templates can be found in the project repository.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: none

dbus-init-delay
Time in seconds which the server waits upon D-Bus initialization to ensure
the D-Bus client is ready to receive signals.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Minimum: 0

Default: 1

listen
One or more IP addresses on which the server listens for incoming queries.
An optional port specification (default is 53) can be appended to each ad-
dress using the @ separator. Use the wildcard address 0.0.0.0 for all con-
figured IPv4 addresses or :: for all configured IPv6 addresses. On Linux, a
wildcard address can be followed by % and an interface name to limit wild-
card binding to a specific interface. A filesystem path can be specified to
listen on a local UNIX SOCK_STREAM socket. A non-absolute path (i.e. not
starting with /) is interpreted relative to rundir. Binding to non-local
addresses is automatically enabled if supported by the operating system.

Change of this parameter requires restart of the Knot server to take ef-
fect.

NOTE:
Non-local address binding or wildcard address binding to a specific in-
terface might require setting sysctl -w net.ipv4.ip_nonlocal_bind=1 and
sysctl -w net.ipv6.ip_nonlocal_bind=1.

Default: not set

listen-quic
One or more IP addresses and optionally ports (default is 853) on which the
server listens for incoming queries over QUIC protocol.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: not set

listen-tls
One or more IP addresses and optionally ports (default is 853) on which the
server listens for incoming queries over TLS protocol (DoT).

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: not set

XDP SECTION
Various options related to XDP listening, especially TCP.

xdp:
listen: STR[@INT] | ADDR[@INT] ...
udp: BOOL
tcp: BOOL
quic: BOOL
quic-port: INT
tcp-max-clients: INT
tcp-inbuf-max-size: SIZE
tcp-outbuf-max-size: SIZE
tcp-idle-close-timeout: TIME
tcp-idle-reset-timeout: TIME
tcp-resend-timeout: TIME
route-check: BOOL
zero-copy: BOOL
ring-size: INT
busypoll-budget: INT
busypoll-timeout: INT

CAUTION:
When you change configuration parameters dynamically or via configura-
tion file reload, some parameters in the XDP section require restarting
the Knot server so that the changes take effect.

listen
One or more network device names (e.g. ens786f0) on which the Mode XDP is
enabled. Alternatively, an IP address can be used instead of a device name,
but the server will still listen on all addresses belonging to the same in-
terface! Optional port specification (default is 53) can be appended to
each device name or address using @ separator.

Change of this parameter requires restart of the Knot server to take ef-
fect.

CAUTION:
If XDP workers only process regular DNS traffic over UDP, it is strongly
recommended to also listen on the addresses which are intended to offer
the DNS service, at least to fulfil the DNS requirement for working TCP.

NOTE:
Incoming DDNS over XDP isn't supported. The server always responds with
SERVFAIL.

Default: not set

udp
If enabled, DNS over UDP is processed with XDP workers.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: on

tcp
If enabled, DNS over TCP traffic is processed with XDP workers.

The TCP stack limitations:

* Congestion control is not implemented.

* Lost packets that do not contain TCP payload may not be resend.

* Not optimized for transfers of non-trivial zones.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: off

quic
If enabled, DNS over QUIC is processed with XDP workers.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: off

quic-port
DNS over QUIC will listen on the interfaces configured by listen, but on
different port, configured by this option.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: 853

tcp-max-clients
A maximum number of TCP clients connected in parallel.

Minimum: 1024

Default: 1000000 (one million)

tcp-inbuf-max-size
Maximum cumulative size of memory used for buffers of incompletely received
messages.

Minimum: 1M (1 MiB)

Default: 100M (100 MiB)

tcp-outbuf-max-size
Maximum cumulative size of memory used for buffers of unACKed sent mes-
sages.

Minimum: 1M (1 MiB)

Default: 100M (100 MiB)

tcp-idle-close-timeout
Time in seconds, after which any idle connection is gracefully closed.

Minimum: 1

Default: 10

tcp-idle-reset-timeout
Time in seconds, after which any idle connection is forcibly closed.

Minimum: 1

Default: 20

tcp-resend-timeout
Resend outgoing data packets (with DNS response payload) if not ACKed be-
fore this timeout (in seconds).

Minimum: 1

Default: 5

route-check
If enabled, routing information from the operating system is considered
when processing every incoming DNS packet received over the XDP interface:

* If the outgoing interface of the corresponding DNS response differs from
the incoming one, the packet is processed normally by UDP/TCP workers
(XDP isn't used).

* If the destination address is blackholed, unreachable, or prohibited, the
DNS packet is dropped without any response.

* The destination MAC address and possible VLAN tag for the response are
taken from the routing system.

If disabled, symmetrical routing is applied. It means that the query source
MAC address is used as a response destination MAC address. Possible VLAN
tag is preserved.

Change of this parameter requires restart of the Knot server to take ef-
fect.

NOTE:
This mode requires forwarding enabled on the loopback interface (sysctl
-w net.ipv4.conf.lo.forwarding=1 and sysctl -w net.ipv6.conf.lo.forward-
ing=1). If forwarding is disabled, all incoming DNS packets are
dropped!

Only VLAN 802.1Q is supported.

Default: off

zero-copy
If enabled and supported by the configured network device, zero-copy mode
can be used. For testing purposes or if there is an issue with the kernel
or device driver, disabling zero-copy may help, at the cost of lower per-
formance.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: on

ring-size
Size of RX, FQ, TX, and CQ rings.

Change of this parameter requires restart of the Knot server to take ef-
fect.

NOTE:
This value should be at least as high as the configured RX size of the
network device in the XDP mode.

Default: 2048

busypoll-budget
If set to a positive value, preferred busy polling is enabled with the
specified budget.

Change of this parameter requires restart of the Knot server to take ef-
fect.

NOTE:
Preferred busy polling also requires setting napi_defer_hard_irqs and
gro_flush_timeout for the appropriate network interface. E.g.:

echo 2 | sudo tee /sys/class/net/<interface>/napi_defer_hard_irqs
echo 200000 | sudo tee /sys/class/net/<interface>/gro_flush_timeout

NOTE:
A recommended value is between 8 and 64.

Default: 0 (disabled)

busypoll-timeout
Timeout in microseconds of preferrred busy polling if enabled by
busypoll-budget.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: 20 (20 microseconds)

CONTROL SECTION
Configuration of the server control interface.

control:
listen: STR ...
backlog: INT
timeout: TIME

listen
A UNIX socket path where the server listens for control commands.

Multiple sockets can be configured for parallel independent use, but their
number is limited (currently to 4), and some operations might be delayed
due to mutexes.

WARNING:
Transaction-like operations, such as conf-begin/set/commit/abort or
zone-begin/set/commit/abort, must be performed using the same socket.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: rundir/knot.sock

backlog
The control UNIX socket listen backlog size.

Change of this parameter requires restart of the Knot server to take ef-
fect.

Default: 5

timeout
Maximum time (in seconds) the control socket operations can take. Set to 0
for infinity.

Default: 5

LOG SECTION
Server can be configured to log to the standard output, standard error out-
put, syslog (or systemd journal if systemd is enabled) or into an arbitrary
file.

There are 6 logging severity levels:

* critical a Non-recoverable error resulting in server shutdown.

* error a Recoverable error, action should be taken.

* warning a Warning that might require user action.

* notice a Server notice or hint.

* info a Informational message.

* debug a Debug or detailed message.

In the case of a missing log section, warning or more serious messages will
be logged to both standard error output and syslog. The info and notice
messages will be logged to standard output.

target
A logging output.

Possible values:

* stdout a Standard output.

* stderr a Standard error output.

* syslog a Syslog or systemd journal.

* file_name a A specific file.

With syslog target, syslog service is used. However, if Knot DNS has been
compiled with systemd support and operating system has been booted with
systemd, systemd journal is used for logging instead of syslog.

A file_name may be specified as an absolute path or a path relative to the
knotd startup directory.

server
Minimum severity level for messages related to general operation of the
server to be logged.

Default: not set

control
Minimum severity level for messages related to server control to be logged.

Default: not set

zone
Minimum severity level for messages related to zones to be logged.

Default: not set

quic
Minimum severity level for messages related to QUIC to be logged.

Default: not set

any
Minimum severity level for all message types, except quic, to be logged.

Default: not set

STATISTICS SECTION
Periodic server statistics dumping.

statistics:
timer: TIME
file: STR
append: BOOL

timer
A period (in seconds) after which all available statistics metrics will by
written to the file.

Default: not set

file
A file path of statistics output in the YAML format.

Default: rundir/stats.yaml

append
If enabled, the output will be appended to the file instead of file re-
placement.

Default: off

DATABASE SECTION
Configuration of databases for zone contents, DNSSEC metadata, or event
timers.

database:
storage: STR
journal-db: STR
journal-db-mode: robust | asynchronous
journal-db-max-size: SIZE
kasp-db: STR
kasp-db-max-size: SIZE
timer-db: STR
timer-db-max-size: SIZE
timer-db-sync: never | shutdown | immediate | TIME
catalog-db: str
catalog-db-max-size: SIZE
zone-db-listen: ADDR[@INT] | STR[@INT] ...
zone-db-tls: BOOL
zone-db-cert-key: BASE64 ...
zone-db-cert-hostname: STR ...

storage
A data directory for storing journal, KASP, and timer databases. A non-ab-
solute path is relative to the knotd startup directory.

Default: ${localstatedir}/lib/knot (configured with --with-storage=path)

journal-db
An explicit specification of the persistent journal database directory.

Default: storage/journal

journal-db-mode
Specifies journal LMDB backend configuration, which influences performance
and durability.

Possible values:

* robust a The journal database disk synchronization ensures database dura-
bility but is generally slower.

* asynchronous a The journal database disk synchronization is optimized for
better performance at the expense of lower database durability in the
case of a crash. This mode is recommended on secondary servers with many
zones.

Default: robust

journal-db-max-size
The hard limit for the journal database maximum size. There is no cleanup
logic in journal to recover from reaching this limit. Journal simply starts
refusing changes across all zones. Decreasing this value has no effect if
it is lower than the actual database file size.

It is recommended to limit journal-max-usage per-zone instead of
journal-db-max-size in most cases. Please keep this value larger than the
sum of all zones' journal usage limits. See more details regarding journal
behaviour.

NOTE:
This value also influences server's usage of virtual memory.

Default: 20G (20 GiB), or 512M (512 MiB) for 32-bit

kasp-db
An explicit specification of the KASP database directory.

Default: storage/keys

kasp-db-max-size
The hard limit for the KASP database maximum size.

NOTE:
This value also influences server's usage of virtual memory.

Default: 10G (10 GiB), or 512M (512 MiB) for 32-bit

timer-db
An explicit specification of the persistent timer database directory.

Default: storage/timers

timer-db-max-size
The hard limit for the timer database maximum size.

NOTE:
This value also influences server's usage of virtual memory.

Default: 5G (5 GiB), or 512M (512 MiB) for 32-bit

timer-db-sync
Specifies when zone timers should be written to the persistent timer data-
base.

Possible values:

* never a Never written.

* shutdown a Written once when the server is shut down.

* immediate a Each zone writes its timers whenever they are modified. This
mode might slow down zones' events if many zones are configured.

* INT a A dedicated thread continuously iterates through the configured
zones and writes their timers at the specified non-zero interval (in sec-
onds).

Default: shutdown

catalog-db
An explicit specification of the zone catalog database directory. Only use-
ful if Catalog zones are enabled.

Default: storage/catalog

catalog-db-max-size
The hard limit for the catalog database maximum size.

NOTE:
This value also influences server's usage of virtual memory.

Default: 20G (20 GiB), or 512M (512 MiB) for 32-bit

zone-db-listen
An ordered list of IP addresses or hostnames, and optionally ports (default
is 6379), or absolute UNIX socket paths (starting with /) of running Redis
(or compatible) instances to be used for reading and/or writing zone con-
tents. See zone-db-input and zone-db-output.

The listen parameters are tried sequentially until a usable connection is
established. The connected database can be a master, a replica, or a sen-
tinel. If it is a sentinel, it is used to acquire connection parameters of
a master database.

Default: not set

zone-db-tls
If enabled, TLS 1.3 will be used for communication with the zone database.

Default: off

zone-db-cert-key
An ordered list of up to 4 public key PINs of the zone database's certifi-
cate. If the list is non-empty, communication with the zone database is
only possible over TLS, and a peer certificate is required. The peer cer-
tificate's public key must match one of the specified PINs.

Default: not set

zone-db-cert-hostname
An ordered list of up to 4 hostnames to be matched against the zone data-
base's certificate. At least one hostname must match for the certificate to
be considered valid (see ca-file). If the list is non-empty, communication
with the zone database is only possible over TLS, and a peer certificate is
required.

Default: not set

KEYSTORE SECTION
DNSSEC keystore configuration.

keystore:
- id: STR
backend: pem | pkcs11
config: STR
ksk-only: BOOL
key-label: BOOL

id
A keystore identifier.

backend
A key storage backend type.

Possible values:

* pem a PEM files.

* pkcs11 a PKCS #11 storage.

Default: pem

config
A backend specific configuration. A directory with PEM files (the path can
be specified as a relative path to kasp-db) or a configuration string for
PKCS #11 storage (<pkcs11-uri> <module-path>). The PKCS #11 URI Scheme is
defined in RFC 7512.

NOTE:
Example configuration string for PKCS #11:

"pkcs11:token=knot;pin-value=1234 /usr/lib64/pkcs11/libsofthsm2.so"

Default: kasp-db/keys

ksk-only
Newly generated keys are stored in this keystore only if they are KSKs or
CSKs. Zone signing keys will be stored in subsequent keystore without this
option enabled.

Default: off

key-label
If enabled in combination with the PKCS #11 backend, generated keys are la-
beled in the form <zone_name> KSK|ZSK.

Default: off

KEY SECTION
Shared TSIG keys used to authenticate communication with the server.

id
A key name identifier.

NOTE:
This value MUST be exactly the same as the name of the TSIG key on the
opposite primary/secondary server(s).

algorithm
A TSIG key algorithm. See TSIG Algorithm Numbers.

Possible values:

* hmac-md5

* hmac-sha1

* hmac-sha224

* hmac-sha256

* hmac-sha384

* hmac-sha512

Default: hmac-sha256

secret
Shared key secret.

Default: not set

REMOTE SECTION
Definitions of remote servers for outgoing connections (source of a zone
transfer, target for a notification, etc.).

remote:
- id: STR
address: ADDR[@INT] | STR ...
via: ADDR[@INT] ...
quic: BOOL
tls: BOOL
key: key_id
cert-key: BASE64 ...
cert-hostname: STR ...
block-notify-after-transfer: BOOL
no-edns: BOOL
automatic-acl: BOOL

id
A remote identifier.

address
An ordered list of destination IP addresses or UNIX socket paths which are
used for communication with the remote server. Non-absolute path (i.e. not
starting with /) is relative to rundir. Optional destination port (default
is 53 for UDP/TCP and 853 for QUIC) can be appended to the address using @
separator. The addresses are tried in sequence until the remote is
reached.

Default: not set

NOTE:
If the remote is contacted and it refuses to perform requested action,
no more addresses will be tried for this remote.

via
An ordered list of source IP addresses which are used as source addresses
for communication with the remote. For the N-th remote address, the last,
but at most N-th, specified via address of the same family is used. This
option can help if the server listens on more addresses. Optional source
port (default is random) can be appended to the address using @ separator.

Default: not set

NOTE:
For the following configuration:

remote:
- id: example
address: [198.51.100.10, 2001:db8::10, 198.51.100.20, 2001:db8::20]
via: [198.51.100.1, 198.51.100.2, 2001:db8::1]

the (via -> address) mapping is:

* 198.51.100.1 -> 198.51.100.10

* 2001:db8::1 -> 2001:db8::10

* 198.51.100.2 -> 198.51.100.20

* 2001:db8::1 -> 2001:db8::20

quic
If this option is set, the QUIC protocol will be used for outgoing communi-
cation with this remote.

NOTE:
One connection per each remote is opened; remote-pool-limit does not
take effect for QUIC. However, fast QUIC handshakes utilizing obtained
session tickets are used for reopening connections to recently (up to 1
day) queried remotes.

Default: off

tls
If this option is set, the TLS (DoT) protocol will be used for outgoing
communication with this remote.

Default: off

key
A reference to the TSIG key which is used to authenticate the communication
with the remote server.

Default: not set

cert-key
An ordered list of up to 4 remote certificate public key PINs. If the list
is non-empty, communication with the remote is only possible via QUIC or
TLS protocols, and a peer certificate is required. The peer certificate key
must match one of the specified PINs.

A PIN is a unique identifier that represents the public key of the peer
certificate. It's a base64-encoded SHA-256 hash of the public key. This
identifier usually remains the same on a certificate renewal.

Default: not set

cert-hostname
An ordered list of up to 4 hostnames to match against peer's certificate.
At least one must match for successful certificate validation (see
ca-file). If the list is non-empty, communication with the remote is only
possible via QUIC or TLS protocols, and a peer certificate is required.

Default: not set

block-notify-after-transfer
When incoming AXFR/IXFR from this remote (as a primary server), suppress
sending NOTIFY messages to all configured secondary servers.

Default: off

no-edns
If enabled, no OPT record (EDNS) is inserted to outgoing requests to this
remote server. This mode is necessary for communication with some broken
DNS implementations (e.g. Windows Server 2016).

Additionally, if TCP is used for zone refresh, the SOA query and the subse-
quent AXFR/IXFR query do not share the same TCP connection. This mode al-
lows transfers from some broken DNS implementations (e.g. ixfrdist).

NOTE:
This option effectively disables zone expire timer updates via EDNS EX-
PIRE option specified in RFC 7314.

Default: off

automatic-acl
If enabled, some authorized operations for the remote are automatically al-
lowed based on the context:

* Incoming NOTIFY is allowed from the remote if it's configured as a
primary server for the zone.

* Outgoing zone transfer is allowed to the remote if it's configured as a
NOTIFY target for the zone.

Automatic ACL rules are evaluated before explicit zone ACL configuration.

NOTE:
This functionality requires global activation via automatic-acl in the
server section.

Default: on

REMOTES SECTION
Definitions of groups of remote servers. Remote grouping can simplify the
configuration.

remotes:
- id: STR
remote: remote_id ...

id
A remote group identifier.

remote
An ordered list of references to remote server definitions.

Default: not set

ACL SECTION
Access control list rule definitions. An ACL rule is a description of one
or more authorized actions (zone transfer request, zone change notifica-
tion, and dynamic DNS update) which are allowed to be processed or denied.
Queries which don't require authorization are always allowed.

id
An ACL rule identifier.

address
An ordered list of IP addresses, absolute UNIX socket paths, network sub-
nets, or network ranges. The query's source address must match one of them.
If this item is not set, address match is not required.

Default: not set

key
An ordered list of references to TSIG keys. The query must match one of
them. If this item is not set, transaction authentication is not used.

Default: not set

cert-key
An ordered list of remote certificate public key PINs. If the list is
non-empty, communication with the remote is only possible via QUIC or TLS
protocols, and a peer certificate is required. The peer certificate key
must match one of the specified PINs.

Default: not set

cert-hostname
An ordered list of hostnames to match against peer's certificate. At least
one must match for successful certificate validation (see ca-file). If the
list is non-empty, communication with the remote is only possible via QUIC
or TLS protocols, and a peer certificate is required.

Default: not set

remote
An ordered list of references remote and remotes. The query must match the
remote parameters.

NOTE:
This option cannot be combined with the address, key, protocol,
cert-key, or cert-hostname option in the same ACL rule.

Default: not set

action
An ordered list of allowed, or denied, actions (request types).

Possible values:

* query a Allow regular DNS query. As normal queries are always allowed,
this action is only useful in combination with TSIG key.

* notify a Allow incoming notify (NOTIFY).

* transfer a Allow zone transfer (AXFR, IXFR).

* update a Allow zone updates (DDNS).

Default: query

protocol
List of allowed protocols.

Possible values:

* udp a UDP protocol.

* tcp a TCP protocol.

* tls a TLS protocol.

* quic a QUIC protocol.

Default: not set (any)

deny
If enabled, instead of allowing, deny the matching combination of the spec-
ified items.

Default: off

update-type
A list of allowed types of Resource Records in a zone update. Every record
in an update must match one of the specified types.

Default: not set

update-owner
This option restricts possible owners of Resource Records in a zone update
by comparing them to either the TSIG key identity, the current zone name,
or to a list of domain names given by the update-owner-name option. The
comparison method is given by the update-owner-match option.

Possible values:

* key a The owner of each updated RR must match the identity of the TSIG
key if used.

* name a The owner of each updated RR must match at least one name in the
update-owner-name list.

* zone a The owner of each updated RR must match the current zone name.

Default: not set

update-owner-match
This option defines how the owners of Resource Records in an update are
matched to the domain name(s) set by the update-owner option.

Possible values:

* sub-or-equal a The owner of each RR in an update must either be equal to
or be a subdomain of at least one domain name set by update-owner.

* equal a The owner of each updated RR must be equal to at least one domain
name set by update-owner.

* sub a The owner of each updated RR must be a subdomain of, but MUST NOT
be equal to at least one domain name set by update-owner.

* pattern a The owner of each updated RR must match a pattern specified by
update-owner. The pattern can be an arbitrary FQDN or non-FQDN domain
name. If a label consists of one * (asterisk) character, it matches any
label. More asterisk labels can be specified.

Default: sub-or-equal

update-owner-name
A list of allowed owners of RRs in a zone update used with update-owner set
to name. Every listed owner name which is not FQDN (i.e. it doesn't end in
a dot) is considered as if it was appended with the target zone name. Such
a relative owner name specification allows better ACL rule reusability
across multiple zones.

Default: not set

SUBMISSION SECTION
Parameters of KSK submission checks.

submission:
- id: STR
parent: remote_id | remotes_id ...
check-interval: TIME
timeout: TIME
parent-delay: TIME

id
A submission identifier.

parent
A list of references remote and remotes to parent's DNS servers to be
checked for presence of corresponding DS records in the case of KSK submis-
sion. All of them must have a corresponding DS for the rollover to con-
tinue. If none is specified, the rollover must be pushed forward manually.

Default: not set

TIP:
A DNSSEC-validating resolver can be set as a parent.

check-interval
Interval (in seconds) for periodic checks of DS presence on parent's DNS
servers, in the case of the KSK submission.

Default: 1h (1 hour)

timeout
After this time period (in seconds) the KSK submission is automatically
considered successful, even if all the checks were negative or no parents
are configured. Set to 0 for infinity.

Default: 0

parent-delay
After successful parent DS check, wait for this period (in seconds) before
continuing the next key roll-over step. This delay shall cover the propaga-
tion delay of update in the parent zone.

NOTE:
This delay only affects automatic KSK submission with parent queries.
For KSK submission resulting in timeout or manually confirmed by knotc
zone-ksk-submitted, the parent-delay doesn't apply.

Default: 0

DNSKEY-SYNC SECTION
Parameters of DNSKEY dynamic-update synchronization.

dnskey-sync:
- id: STR
remote: remote_id | remotes_id ...
check-interval: TIME

id
A dnskey-sync identifier.

remote
A list of references remote and remotes to other signers or common master,
which the DDNS updates with DNSKEY/CDNSKEY/CDS records shall be sent to.

Default: not set

check-interval
If the last DNSKEY sync failed or resulted in any change, re-check the con-
sistence after this interval (in seconds) and re-try if needed.

Default: 60 (1 minute)

POLICY SECTION
DNSSEC policy configuration.

policy:
- id: STR
keystore: keystore_id ...
manual: BOOL
single-type-signing: BOOL
algorithm: rsasha1 | rsasha1-nsec3-sha1 | rsasha256 | rsasha512 | ecdsap256sha256 | ecdsap384sha384 | ed25519 | ed448
ksk-size: SIZE
zsk-size: SIZE
ksk-shared: BOOL
dnskey-ttl: TIME
zone-max-ttl: TIME
keytag-modulo: INT/INT
ksk-lifetime: TIME
zsk-lifetime: TIME
delete-delay: TIME
propagation-delay: TIME
rrsig-lifetime: TIME
rrsig-refresh: TIME
rrsig-pre-refresh: TIME
reproducible-signing: BOOL
nsec3: BOOL
nsec3-iterations: INT
nsec3-opt-out: BOOL
nsec3-salt-length: INT
nsec3-salt-lifetime: TIME
signing-threads: INT
ksk-submission: submission_id
ds-push: remote_id | remotes_id ...
cds-cdnskey-publish: none | delete-dnssec | rollover | always | double-ds
cds-digest-type: sha256 | sha384
dnskey-management: full | incremental
offline-ksk: BOOL
unsafe-operation: none | no-check-keyset | no-update-dnskey | no-update-nsec | no-update-expired ...

id
A policy identifier.

keystore
A reference to a keystore holding private key material for zones.

If multiple keystores are specified, private keys for signing are looked up
in all of them. But newly generated keys are stored in the first one (or in
the first one without enabled ksk-only in the case of a new ZSK) in the
specified order.

NOTE:
If multiple keystores are configured and a zone is being restored with
the back up feature, all restored private keys are stored into the first
referenced keystore.

NOTE:
A configured keystore called "default" won't be used unless explicitly
referenced.

Default: an imaginary keystore with all default values

manual
If enabled, automatic key management is not used.

Default: off

single-type-signing
If enabled, Single-Type Signing Scheme is used in the automatic key manage-
ment mode.

Default: off (module onlinesign has default on)

algorithm
An algorithm of signing keys and issued signatures. See DNSSEC Algorithm
Numbers.

Possible values:

* rsasha1

* rsasha1-nsec3-sha1

* rsasha256

* rsasha512

* ecdsap256sha256

* ecdsap384sha384

* ed25519

* ed448

NOTE:
Ed448 algorithm is only available if compiled with GnuTLS 3.6.12+ and
Nettle 3.6+.

Default: ecdsap256sha256

ksk-size
A length of newly generated KSK or CSK keys.

Default: 2048 (rsa*), 256 (ecdsap256), 384 (ecdsap384), 256 (ed25519), 456
(ed448)

zsk-size
A length of newly generated ZSK keys.

Default: see default for ksk-size

ksk-shared
If enabled, all zones with this policy assigned will share one or more
KSKs. More KSKs can be shared during a KSK rollover.

WARNING:
As the shared KSK set is bound to the policy id, renaming the policy
breaks this connection and new shared KSK set is initiated when a new
KSK is needed.

Default: off

dnskey-ttl
A TTL value for DNSKEY records added into zone apex.

NOTE:
Has influence over ZSK key lifetime.

WARNING:
Ensure all DNSKEYs with updated TTL are propagated before any subsequent
DNSKEY rollover starts.

Default: zone SOA TTL

zone-max-ttl
Declare (override) maximal TTL value among all the records in zone.

NOTE:
It's generally recommended to override the maximal TTL computation by
setting this explicitly whenever possible. It's required for DNSSEC Of-
fline KSK and really reasonable when records are generated dynamically
(e.g. by a module).

Default: computed after zone is loaded

keytag-modulo
Specifies that the keytags of any generated keys shall be congruent by
specified modulo. The option value must be a string in the format R/M,
where R < M <= 256 are positive integers. Whenever a DNSSEC key is gener-
ated, it is ensured that keytag % M == R. This prevents keytag conflict in
DNSSEC Offline KSK or DNSSEC multi-signer (and possibly other) setups.

NOTE:
This only applies to newly generated keys when they are generated. Keys
from before this option and keys imported from elsewhere might not ful-
fill the policy.

Default: 0/1

ksk-lifetime
A period (in seconds) between KSK generation and the next rollover initia-
tion.

NOTE:
KSK key lifetime is also influenced by propagation-delay, dnskey-ttl,
and KSK submission delay.

Zero (aka infinity) value causes no KSK rollover as a result.

This applies for CSK lifetime if single-type-signing is enabled.

Default: 0 (infinity)

zsk-lifetime
A period (in seconds) between ZSK activation and the next rollover initia-
tion.

NOTE:
More exactly, this period is measured since a ZSK is activated, and af-
ter this, a new ZSK is generated to replace it within following
roll-over.

As a consequence, in normal operation, this results in the period of ZSK
generation being zsk-lifetime + propagation-delay + dnskey_ttl.

Zero (aka infinity) value causes no ZSK rollover as a result.

Default: 30d (30 days)

delete-delay
Once a key (KSK or ZSK) is rolled-over and removed from the zone, keep it
in the KASP database for at least this period (in seconds) before deleting
it completely. This might be useful in some troubleshooting cases when res-
urrection is needed.

Default: 0

propagation-delay
An extra delay added for each key rollover step. This value (in seconds)
should be high enough to cover propagation of data from the primary server
to all secondary servers, as well as the duration of signing routine itself
and possible outages in signing and propagation infrastructure. In other
words, this delay should ensure that within this period of time after
planned change of the key set, all public-facing secondaries will already
serve new DNSKEY RRSet for sure.

NOTE:
Has influence over ZSK key lifetime.

Default: 1h (1 hour)

rrsig-lifetime
A validity period (in seconds) of newly issued signatures.

NOTE:
The RRSIG's signature inception time is set to 90 minutes in the past.
This time period is not counted to the signature lifetime.

Default: 14d (14 days)

rrsig-refresh
A period (in seconds) how long at least before a signature expiration the
signature will be refreshed, in order to prevent expired RRSIGs on sec-
ondary servers or resolvers' caches.

Default: 0.1 * rrsig-lifetime + propagation-delay + zone-max-ttl

If dnssec-validation is enabled:

Default: 1d (1 day)

rrsig-pre-refresh
A period (in seconds) how long at most before a signature refresh time the
signature might be refreshed, in order to refresh RRSIGs in bigger batches
on a frequently updated zone (avoid re-sign event too often).

Default: 1h (1 hour)

reproducible-signing
For ECDSA algorithms, generate RRSIG signatures deterministically (RFC
6979). Besides better theoretical cryptographic security, this mode allows
significant speed-up of loading signed (by the same method) zones. However,
the zone signing is a bit slower.

Default: off

nsec3
Specifies if NSEC3 will be used instead of NSEC.

Default: off

nsec3-iterations
A number of additional times the hashing is performed.

Default: 0

nsec3-opt-out
If set, NSEC3 records won't be created for insecure delegations. This
speeds up the zone signing and reduces overall zone size.

WARNING:
NSEC3 with the Opt-Out bit set no longer works as a proof of non-exis-
tence in this zone.

Default: off

nsec3-salt-length
A length of a salt field in octets, which is appended to the original owner
name before hashing.

Default: 0

nsec3-salt-lifetime
A validity period (in seconds) of newly issued salt field.

Zero value means infinity.

Special value -1 triggers re-salt every time when active ZSK changes. This
optimizes the number of big changes to the zone.

Default: 30d (30 days)

signing-threads
When signing zone or update, use this number of threads for parallel sign-
ing.

Those are extra threads independent of Background workers.

NOTE:
Some steps of the DNSSEC signing operation are not parallelized.

Default: 1 (no extra threads)

ksk-submission
A reference to submission section holding parameters of KSK submission
checks.

Default: not set

ds-push
Optional references remote and remotes to authoritative DNS server of the
parent's zone. The remote server must be configured to accept DS record up-
dates via DDNS. Whenever a CDS record in the local zone is changed, the
corresponding DS record is sent as a dynamic update (DDNS) to the parent
DNS server. All previous DS records are deleted within the DDNS message.
It's possible to manage both child and parent zones by the same Knot DNS
server.

NOTE:
This feature requires cds-cdnskey-publish not to be set to none.

NOTE:
The mentioned change to CDS record usually means that a KSK roll-over is
running and the new key being rolled-in is in "ready" state already for
the period of propagation-delay.

NOTE:
Module Onlinesign doesn't support DS push.

NOTE:
When turning this feature on while a KSK roll-over is already running,
it might not take effect for the already-running roll-over.

Default: not set

dnskey-sync
A reference to dnskey-sync section holding parameters of DNSKEY synchro-
nization.

Default: not set

cds-cdnskey-publish
Controls if and how shall the CDS and CDNSKEY be published in the zone.

Possible values:

* none a Never publish any CDS or CDNSKEY records in the zone.

* delete-dnssec a Publish special CDS and CDNSKEY records indicating turn-
ing off DNSSEC.

* rollover a Publish CDS and CDNSKEY records for ready and not yet active
KSK (submission phase of KSK rollover).

* always a Always publish one CDS and one CDNSKEY records for the current
KSK.

* double-ds a Always publish up to two CDS and two CDNSKEY records for
ready and/or active KSKs.

NOTE:
If the zone keys are managed manually, the CDS and CDNSKEY rrsets may
contain more records depending on the keys available.

WARNING:
The double-ds value does not trigger double-DS roll-over method. That
method is only supported when performed manually, with unset
ksk-submission.

Default: rollover

cds-digest-type
Specify digest type for published CDS records.

Possible values:

* sha256

* sha384

Default: sha256

dnskey-management
Specify how the DNSKEY, CDNSKEY, and CDS RRSets at the zone apex are han-
dled when (re-)signing the zone.

Possible values:

* full a Upon every zone (re-)sign, delete all unknown DNSKEY, CDNSKEY, and
CDS records and keep just those that are related to the zone keys stored
in the KASP database.

* incremental a Keep unknown DNSKEY, CDNSKEY, and CDS records in the zone,
and modify server-managed records incrementally by employing changes in
the KASP database.

NOTE:
Prerequisites for incremental:

* The Offline KSK isn't supported.

* The delete-delay is long enough to cover possible daemon shutdown
(e.g. due to server maintenance).

* Avoided manual deletion of keys with keymgr.

Otherwise there might remain some DNSKEY records in the zone, belonging
to deleted keys.

Default: full

offline-ksk
Specifies if Offline KSK feature is enabled.

Default: off

unsafe-operation
Turn off some DNSSEC safety features.

Possible values:

* none a Nothing disabled.

* no-check-keyset a Don't check active keys in present algorithms. This may
lead to violation of RFC 4035 Section 2.2.

* no-update-dnskey a Don't maintain/update DNSKEY, CDNSKEY, and CDS records
in the zone apex according to KASP database. Juste leave them as they are
in the zone.

* no-update-nsec a Don't maintain/update NSEC/NSEC3 chain. Leave all the
records as they are in the zone.

* no-update-expired a Don't update expired RRSIGs.

Multiple values may be specified.

WARNING:
This mode is intended for DNSSEC experts who understand the correspond-
ing consequences.

Default: none

EXTERNAL SECTION
External zone validation configuration.

external:
- id: STR
timeout: TIME
dump-new-zone: STR
dump-removals: STR
dump-additions: STR

id
An external section identifier.

timeout
If the validation is not confirmed within this time interval in seconds, it
is considered failed.

Default: 300

dump-new-zone
A path to file where the new zone contents will be written before waiting
for external validation.

Default: none

dump-removals
A path to file where the records being removed will be written before wait-
ing for external validation.

Default: none

dump-additions
A path to file where the records being added will be written before waiting
for external validation.

Default: none

TEMPLATE SECTION
A template is shareable zone settings, which can simplify configuration by
reducing duplicates. A special default template (with the default identi-
fier) can be used for global zone configuration or as an implicit configu-
ration if a zone doesn't have another template specified.

template:
- id: STR
global-module: STR/STR ...
# All zone options (excluding 'template' item)

NOTE:
If an item is explicitly specified both in the referenced template and
the zone, the template item value is overridden by the zone item value.

id
A template identifier.

global-module
An ordered list of references to query modules in the form of module_name
or module_name/module_id. These modules apply to all queries.

NOTE:
This option is only available in the default template.

Default: not set

ZONE SECTION
Definition of zones served by the server.

zone:
- domain: DNAME
template: template_id
storage: STR
file: STR
zone-db-input: INT
zone-db-output: INT
master: remote_id | remotes_id ...
ddns-master: remote_id
notify: remote_id | remotes_id ...
notify-delay: TIME
update-delay: TIME
acl: acl_id ...
master-pin-tolerance: TIME
provide-ixfr: BOOL
semantic-checks: BOOL | soft
default-ttl: TIME
zonefile-sync: TIME
zonefile-load: none | difference | difference-no-serial | whole
zonefile-skip: STR ...
journal-content: none | changes | all
journal-max-usage: SIZE
journal-max-depth: INT
ixfr-benevolent: BOOL
ixfr-by-one: BOOL
ixfr-from-axfr: BOOL
zone-max-size : SIZE
adjust-threads: INT
external-validation: external_id
dnssec-signing: BOOL
dnssec-validation: BOOL
dnssec-policy: policy_id
ds-push: remote_id | remotes_id ...
zonemd-verify: BOOL
zonemd-generate: none | zonemd-sha384 | zonemd-sha512 | remove
serial-policy: increment | unixtime | dateserial
serial-modulo: INT/INT | +INT | -INT | INT/INT+INT | INT/INT-INT
reverse-generate: DNAME ...
include-from: DNAME ...
refresh-min-interval: TIME
refresh-max-interval: TIME
retry-min-interval: TIME
retry-max-interval: TIME
expire-min-interval: TIME
expire-max-interval: TIME
catalog-role: none | interpret | generate | member
catalog-template: template_id ...
catalog-zone: DNAME
catalog-group: STR
module: STR/STR ...

domain
A zone name identifier.

template
A reference to a configuration template.

Default: not set or default (if the template exists)

storage
A data directory for storing zone files. A non-absolute path is relative to
the knotd startup directory.

Default: ${localstatedir}/lib/knot (configured with --with-storage=path)

file
A path to the zone file. It is also possible to use the following format-
ters:

* %c[N] or %c[N-M] a Means the Nth character or a sequence of characters
beginning from the Nth and ending with the Mth character of the textual
zone name (see %s). The indexes are counted from 0 from the left. All
dots (including the terminal one) are considered. If the character is not
available, the formatter has no effect.

* %l[N] a Means the Nth label of the textual zone name (see %s). The index
is counted from 0 from the right (0 ~ TLD). If the label is not avail-
able, the formatter has no effect.

* %s a Means the current zone name in the textual representation. The zone
name doesn't include the terminating dot (the result for the root zone is
the empty string!).

* %% a Means the % character.

WARNING:
Beware of special characters which are escaped or encoded in the \DDD
form where DDD is corresponding decimal ASCII code.

Default: storage/%s.zone

zone-db-input
If set, the zone is loaded from the zone database configured at
zone-db-listen. The value of this option specifies the zone instance number
(from 1 to 8 inclusive) within the database to read from.

NOTE:
With this option enabled, the textual zone file is never loaded. The
zonefile-load setting still applies to handling of the zone contents
loaded from the database, however, zonefile-load: whole and journal-con-
tent: changes are recommended (both being the defaults).

Default: -1 (disabled)

zone-db-output
If set, the zone is stored to the zone database configured at
zone-db-listen and updated there with every change to the zone contents.
The value of this option specifies the zone instance number (from 1 to 8
inclusive) within the database to write to.

Default: -1 (disabled)

master
An ordered list of references remote and remotes to zone primary servers
(formerly known as master servers). Empty value is allowed for template
value overriding.

Default: not set

ddns-master
A reference to a zone primary master where DDNS messages should be for-
warded to. If not specified, the first master server is used.

If set to the empty value (""), incoming DDNS messages aren't forwarded but
are applied to the local zone instead, no matter if it is a secondary
server. This is only allowed in combination with dnssec-signing enabled.

Default: not set

notify
An ordered list of references remote and remotes to secondary servers to
which NOTIFY message is sent if the zone changes. Empty value is allowed
for template value overriding.

Default: not set

notify-delay
A time delay in seconds before an outgoing NOTIFY message is sent. This de-
lay also defines the time granularity at which NOTIFY messages are sent per
zone.

Default: 0

update-delay
A time delay in seconds before a change to zone contents is made after an
external trigger such as incoming NOTIFY or DDNS, or an internal trigger
from different zone such as change to zone to be reversed, included from or
a member of generated catalog zone.

Exception: zone changing events triggered by control socket (knotc zone-*
commands) or by interpreted catalog are performed immediately, without con-
figured delay.

Default: 0

acl
An ordered list of references to ACL rules which can allow or disallow zone
transfers, updates or incoming notifies.

Default: not set

master-pin-tolerance
If set to a nonzero value on a secondary, always request AXFR/IXFR from the
same primary as the last time, effectively pinning one primary. Only when
another primary is updated and the current one lags behind for the speci-
fied amount of time (defined by this option in seconds), change to the up-
dated primary and force AXFR.

This option is useful when multiple primaries may have different zone his-
tory in their journals, making it unsafe to combine interchanged IXFR from
different primaries.

Default: 0 (disabled)

provide-ixfr
If disabled, the server is forced to respond with AXFR to IXFR queries. If
enabled, IXFR requests are responded normally.

Default: on

semantic-checks
Selects if extra zone semantic checks are used or impacts of the mandatory
checks.

There are several mandatory checks which are always enabled and cannot be
turned off. An error in a mandatory check causes the zone not to be loaded.
Most of the mandatory checks can be weakened by setting soft, which allows
the zone to be loaded even if the check fails.

If enabled, extra checks are used. These checks don't prevent the zone from
loading.

The mandatory checks are applied to zone files, zone transfers, and updates
via control interface. The extra checks are applied to zone files only!

Mandatory checks:

* Missing SOA record at the zone apex (RFC 1034) (*)

* An extra record exists together with a CNAME record except for RRSIG and
NSEC (RFC 1034)

* Multiple CNAME records with the same owner exist (RFC 1034)

* DNAME record having a record under it (RFC 6672)

* Multiple DNAME records with the same owner exist (RFC 6672)

* NS record exists together with a DNAME record (RFC 6672)

* DS record exists at the zone apex (RFC 3658)

(*) The marked check can't be weakened by the soft mode. All other manda-
tory checks are subject to the optional soft mode.

Extra checks:

* Missing NS record at the zone apex

* Missing glue A or AAAA record

* Invalid DS or NSEC3PARAM record

* CDS or CDNSKEY inconsistency

* All other DNSSEC checks executed during dnssec-validation

NOTE:
The soft mode allows the refresh event to ignore a CNAME response to a
SOA query (malformed message) and triggers a zone bootstrap instead.

Default: off

default-ttl
The default TTL value if none is specified in a zone file or zone insertion
using the dynamic configuration.

WARNING:
As changing this value can result in differently parsed zone file(s),
the corresponding zone SOA serial(s) should be incremented before re-
loading or committing the configuration. Alternatively, setting
zonefile-load to difference-no-serial ensures the resulting zone(s) up-
date is correct.

Default: 3600

zonefile-sync
The time in seconds after which the current zone in memory will be synced
with a zone file on the disk (see file). The server will serve the latest
zone even after a restart using zone journal, but the zone file on the disk
will only be synced after zonefile-sync time has expired (or after manual
zone flush). This is applicable when the zone is updated via IXFR, DDNS or
automatic DNSSEC signing. In order to completely disable automatic zone
file synchronization, set the value to -1. In that case, it is still possi-
ble to force a manual zone flush using the -f option.

NOTE:
If you are serving large zones with frequent updates where the immediate
sync with a zone file is not desirable, increase the value.

Default: 0 (immediate)

zonefile-load
Selects how the zone file contents are applied during zone load.

Possible values:

* none a The zone file is not used at all.

* difference a If the zone contents are already available during server
start or reload, the difference is computed between them and the contents
of the zone file. This difference is then checked for semantic errors and
applied to the current zone contents.

* difference-no-serial a Same as difference, but the SOA serial in the zone
file is ignored, the server takes care of incrementing the serial auto-
matically.

* whole a Zone contents are loaded from the zone file.

When difference is configured and there are no zone contents yet (cold
start and no zone contents in the journal), it behaves the same way as
whole.

Default: whole

NOTE:
See Handling zone file, journal, changes, serials for guidance on con-
figuring these and related options to ensure reliable operation.

WARNING:
If zone-db-input is configured, the textual zone file is never loaded.
However, this option still effects on how the zone contents loaded from
the database are applied and handled.

zonefile-skip
Specifies resource record types to be omitted when loading and syncing zone
files.

Resource record types are represented as strings (e.g. "DS") and multiple
types may be specified. The special string dnssec represents all types usu-
ally created by DNSSEC signing routines (DNSKEY, RRSIG, NSEC, NSEC3,
NSEC3PARAM, CDNSKEY, CDS a but not DS).

NOTE:
This option takes effect while a zone file is being read or written, but
it does not directly trigger any zone file operation. Therefore, the
configured record types cannot be expected to disappear from the zone
file or running zone immediately after setting the option.

Default: not set

journal-content
Selects how the journal shall be used to store zone and its changes.

Possible values:

* none a The journal is not used at all.

* changes a Zone changes history is stored in journal.

* all a Zone contents and history is stored in journal.

Default: changes

WARNING:
When this option is changed, the journal still contains data respective
to the previous setting. For example, changing it to none does not purge
the journal. Also, changing it from all to changes does not cause the
deletion of the zone-in-journal and the behaviour of the zone loading
procedure might be different than expected. It is recommended to con-
sider purging the journal when this option is changed.

journal-max-usage
Policy how much space in journal DB will the zone's journal occupy.

NOTE:
Journal DB may grow far above the sum of journal-max-usage across all
zones, because of DB free space fragmentation.

Default: 100M (100 MiB)

journal-max-depth
Maximum history length of the journal.

NOTE:
Zone-in-journal changeset isn't counted to the limit.

Minimum: 2

Default: 20

ixfr-benevolent
If enabled, incoming IXFR is applied even when it contains removals of
non-existing or additions of existing records.

Default: off

ixfr-by-one
Within incoming IXFR, process only one changeset at a time, not multiple
together. This preserves the complete history in the journal and prevents
the merging of changesets when multiple changesets are IXFRed simultane-
ously. However, this does not prevent the merging (or deletion) of old
changesets in the journal to save space, as described in journal behaviour.

This option leads to increased server load when processing IXFR, including
network traffic.

Default: off

ixfr-from-axfr
If a primary sends AXFR-style-IXFR upon an IXFR request, compute the dif-
ference and process it as an incremental zone update (e.g. by storing the
changeset in the journal).

Default: off

zone-max-size
Maximum size of the zone. The size is measured as size of the zone records
in wire format without compression. The limit is enforced for incoming zone
transfers and dynamic updates.

For incremental transfers (IXFR), the effective limit for the total size of
the records in the transfer is twice the configured value. However the fi-
nal size of the zone must satisfy the configured value.

Default: unlimited

adjust-threads
Parallelize internal zone adjusting procedures by using specified number of
threads. This is useful with huge zones with NSEC3. Speedup observable at
server startup and while processing NSEC3 re-salt.

Default: 1 (no extra threads)

external-validation
A reference to external validation section.

If configured, every change to the zone (zone file update, incoming
IXFR/AXFR, dynamic update, and DNSSEC re-signing, but not changes over con-
trol socket a knotc zone-begin) is paused just before applying the new
zone. At that point, validation and confirmation is awaited from the user
(or potentially a user-defined script).

NOTE:
In the case of server shutdown or configuration reload, the server waits
until all outstanding external validations are either committed or
aborted, or until the timeout elapses.

In the referenced external section, it is possible to define paths to files
where the new zone contents and/or differences are written (in the zone
file format) just before every validation.

TIP:
If dbus-event is set to external-verify, a corresponding signal is emit-
ted when the server is awaiting external validation.

Default: none

dnssec-signing
If enabled, automatic DNSSEC signing for the zone is turned on.

Default: off

dnssec-validation
If enabled, the zone contents are validated for being correctly signed (in-
cluding NSEC/NSEC3 chain) with DNSSEC signatures every time the zone is
loaded or changed (including AXFR/IXFR), or whenever a previously seen
RRSIG's expiration has passed.

When the validation fails, the zone being loaded or update being applied is
cancelled with an error, and either none or previous zone state is pub-
lished.

When a RRSIG expires on a secondary server, the whole zone is expired (per-
manent SERVFAIL until resolved).

The DNSSEC validation is performed incrementally (taking little time for
small updates to large zone) whenever possible, but occasionally full zone
validation takes place.

List of DNSSEC checks:

* Every zone RRSet is correctly signed by at least one present DNSKEY.

* For every RRSIG there are at most 3 non-matching DNSKEYs with the same
keytag.

* DNSKEY RRSet is signed by KSK.

* NSEC(3) RR exists for each name (unless opt-out) with correct bitmap.

* Every NSEC(3) RR is linked to the lexicographically next one.

The validation is not affected by dnssec-policy configuration, except for
signing-threads option, which specifies the number of threads for parallel
validation, and rrsig-refresh, which defines minimal allowed remaining
RRSIG validity (otherwise a warning is logged).

NOTE:
Redundant or garbage NSEC3 records are ignored.

This mode is not compatible with dnssec-signing.

TIP:
If dbus-event is set to dnssec-invalid, a corresponding signal is emit-
ted when the validation fails, both in the case of an invalid zone up-
date and in the case of an expired RRSIG that has not been refreshed.

Default: not set

dnssec-policy
A reference to DNSSEC signing policy.

NOTE:
A configured policy called "default" won't be used unless explicitly
referenced.

Default: an imaginary policy with all default values

ds-push
Per zone configuration of ds-push. This option overrides possible per pol-
icy option. Empty value is allowed for template value overriding.

Default: not set

zonemd-verify
On each zone load/update, verify that ZONEMD is present in the zone and
valid.

NOTE:
Zone digest calculation may take much time and CPU on large zones.

TIP:
If dbus-event is set to dnssec-invalid, a corresponding signal is emit-
ted when the verification fails.

Default: off

zonemd-generate
On each zone update, calculate ZONEMD and put it into the zone.

Possible values:

* none a No action regarding ZONEMD.

* zonemd-sha384 a Generate ZONEMD using SHA384 algorithm.

* zonemd-sha512 a Generate ZONEMD using SHA512 algorithm.

* remove a Remove any ZONEMD from the zone apex.

Default: none

serial-policy
Specifies how the zone serial is updated after a dynamic update or auto-
matic DNSSEC signing. If the serial is changed by the dynamic update, no
change is made.

Possible values:

* increment a The serial is incremented according to serial number arith-
metic.

* unixtime a The serial is set to the current unix time.

* dateserial a The 10-digit serial (YYYYMMDDnn) is incremented, the first 8
digits match the current iso-date.

NOTE:
If the resulting serial for unixtime or dateserial is lower than or
equal to the current serial (this happens e.g. when migrating from other
policy or frequent updates), the serial is incremented instead.

To avoid user confusion, use dateserial only if you expect at most 100
updates per day per zone and unixtime only if you expect at most one up-
date per second per zone.

Generated catalog zones use unixtime only.

Default: increment (unixtime for generated catalog zones)

serial-modulo
The option value is a string consisting of two parts (with no separator be-
tween them), each of which is optional.

The first part specifies that the zone serials must be congruent modulo the
specified value. The format is R/M, where R < M <= 256 are positive inte-
gers. Whenever the zone serial is incremented, it is ensured that serial %
M == R. This can be useful in the case of multiple inconsistent primaries,
where distinct zone serial sequences prevent cross-master-IXFR by any sec-
ondary.

NOTE:
Because the zone serial effectively always increments by M instead of 1,
it is not recommended to use dateserial or even unixtime serial-policy
in the case of rapidly updated zone.

The second part specifies a numeric shift for the generated zone serial.
The shift is formatted as a signed integer, including the sign (+ or -).
It is mostly useful with unixtime serial-policy, where the generated zone
serial is shifted relative to the Unix time.

NOTE:
In order to ensure the congruent policy, this option is only allowed
with DNSSEC signing enabled and zonefile-load to be either differ-
ence-no-serial or none.

Default: 0/1+0

reverse-generate
A list of zone names for which automatic generation of reverse PTR records
based on A/AAAA records is enabled. The entire generated zone is automati-
cally stored in the journal.

The auto-generated reverse zone is re-generated whenever any of the speci-
fied zones is updated. This includes the situation when reverse generation
had failed due to some of the specified zones were not yet loaded or had
expired.

Current limitations:

* Is slow for large zones (even when changing a little).

* Recomputes all reverse records upon any change in any of the reversed
zones.

In case of secondary zone (i.e. master is specified) this option implies
ixfr-from-axfr: on and journal-content: all, otherwise zonefile-load: dif-
ference-no-serial and journal-content: all.

Default: none

include-from
A list of subzones that should be flattened into this zone. The flattening
deletes all delegation-related records (including NS, SOA, ...) from both
zones and copies all other records from the subzone to this zone.

In case of secondary zone (i.e. master is specified) this option implies
ixfr-from-axfr: on and journal-content: all, otherwise zonefile-load: dif-
ference-no-serial and journal-content: all.

Default: none

refresh-min-interval
Forced minimum zone refresh interval (in seconds) to avoid flooding primary
server.

Minimum: 2

Default: 2

refresh-max-interval
Forced maximum zone refresh interval (in seconds).

Default: not set

retry-min-interval
Forced minimum zone retry interval (in seconds) to avoid flooding primary
server.

Minimum: 1

Default: 1

retry-max-interval
Forced maximum zone retry interval (in seconds).

Default: not set

expire-min-interval
Forced minimum zone expire interval (in seconds) to avoid flooding primary
server.

Minimum: 3

Default: 3

expire-max-interval
Forced maximum zone expire interval (in seconds).

Default: not set

catalog-role
Trigger zone catalog feature. Possible values:

* none a Not a catalog zone.

* interpret a A catalog zone which is loaded from a zone file or XFR, and
member zones shall be configured based on its contents.

* generate a A catalog zone whose contents are generated according to as-
signed member zones.

* member a A member zone that is assigned to one generated catalog zone.

NOTE:
If set to generate, the zonefile-load option has no effect since a zone
file is never loaded.

Default: none

catalog-template
For the catalog member zones, the specified configuration template will be
applied.

Multiple catalog templates may be defined. The first one is used unless the
member zone has the group property defined, matching another catalog tem-
plate.

NOTE:
This option must be set if and only if catalog-role is interpret.

Nested catalog zones aren't supported. Therefore catalog templates can't
contain catalog-role set to interpret or generate.

Default: not set

catalog-zone
Assign this member zone to specified generated catalog zone.

NOTE:
This option must be set if catalog-role is member.

The referenced catalog zone must exist and have catalog-role set to gen-
erate.

WARNING:
Atomically changing a member zone from one catalog zone to another that
is consumed by the same secondary is not recommended, as the update to
the target catalog zone may be randomly processed first and ignored due
to a clash between catalogs.

The correct catalog zone processing order on secondaries can be achieved
by temporarily freezing outgoing transfers of the target catalog zone
and thawing it after the source catalog zone has already been processed
(i.e. the member has been removed), and then manually notifying the sec-
ondaries.

If the generated zone catalogs have already arrived at a secondary in
the wrong order, triggering a zone retransfer of the target catalog on
the secondary fixes the situation.

Default: not set

catalog-group
Assign this member zone to specified catalog group (configuration tem-
plate).

NOTE:
This option has an effect if and only if catalog-role is member.

Default: not set

module
An ordered list of references to query modules in the form of module_name
or module_name/module_id. These modules apply only to the current zone
queries.

Default: not set

AUTHOR
CZ.NIC, z.s.p.o. and contributors <https://www.knot-dns.cz/>

3.5.6 2026-07-20 KNOT.CONF(5)

Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=knot.conf&sektion=5&manpath=FreeBSD+Ports+15.1.quarterly>

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