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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 mean-
ing of the following symbols:

• INT Integer

• STR Textual string

• HEXSTR Hexadecimal string (with 0x prefix)

• BOOL Boolean value (on/off or true/false)

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

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

• BASE64 Base64 encoded string

• ADDR IPv4 or IPv6 address

• DNAME Domain name

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

• [ ] Optional value

• | Choice

The configuration consists of several fixed sections and optional mod-
ule sections. There are 18 fixed sections (module, server, xdp, con-
trol, log, statistics, database, keystore, key, remote, remotes, acl,
submission, dnskey-sync, policy, external`, template, zone). Module
sections are prefixed 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
reference 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
necessary 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 relative 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 using the comment item which is stored in the server beside the
configuration.

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

include: STR

include
A path or a matching pattern specifying one or more files that are in-
cluded at the place of the include option position in the configura-
tion. If the path is not absolute, then it is considered to be rela-
tive to the current file. The pattern can be an arbitrary string meet-
ing POSIX glob requirements, 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 configura-
tion in the configuration database when including a configuration file
or ensures that some configuration wasn't specified in previous in-
cludes.

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

• clear: zone Clears the zone section.

• clear: mod-* Clears all module sections.

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

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

• clear: @(zone|template) (GNU only) Clears the zone and template
sections.

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 suf-
fix.

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
system directories. See man dlopen for more details.

Default: ${libdir}/knot/modules-${version}/module_name.so (or
${path}/module_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[@INT] | STR ...
listen-quic: ADDR[@INT] ...
listen-tls: ADDR[@INT] ...

CAUTION:
When you change configuration parameters dynamically or via configu-
ration file reload, some parameters in the Server section require
restarting the Knot server so that the changes take effect. See be-
low 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 dis-
able.

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-absolute 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 capa-
bilities are employed if supported.

Change of this parameter requires restart of the Knot server to take
effect.

Default: root:root

pidfile
A PID file location.

Change of this parameter requires restart of the Knot server to take
effect.

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
effect.

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
effect.

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
effect.

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
responding immediately with SERVFAIL answers until the zone loads.

Default: off

tcp-idle-timeout
Maximum idle time (in seconds) between requests on an inbound TCP con-
nection. 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 process-
ing. Set to 0 for infinity.

Default: 500 (milliseconds)

CAUTION:
In order to reduce the risk of Slow Loris attacks, it's recommended
setting 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_REUSE-
PORT_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
effect.

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_en-
able 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
effect.

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:
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 ex-
pected.

Change of this parameter requires restart of the Knot server to take
effect.

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
effect.

Minimum: 1

Default: 4

remote-pool-limit
If nonzero, the server will keep up to this number of outgoing TCP con-
nections 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
effect.

Default: 0

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

Default: 5

remote-retry-delay
When a connection attempt times out to some remote address, this infor-
mation will be kept for this specified time (in milliseconds) and other
connections 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
network sockets are bound to UDP and TCP workers in order to increase
the networking performance. This mode isn't recommended for setups
where the number 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
effect.

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 com-
munication. A non-absolute path of a user specified key file is rela-
tive 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 systems 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 supported 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 No signal is emitted.

• running There are two possible signals emitted:

• started when the server is started and all configured zones (in-
cluding catalog zones and their members) are loaded or successfully
bootstrapped.

• stopped when the server shutdown sequence is initiated.

• zone-updated The signal zone_updated is emitted when a zone has been
updated; the signal parameters are zone name and zone SOA serial.

• external-verify - The signal external_verify is emitted when a zone
is awaiting external validation before applying the changes; the sig-
nal parameter is zone name.

• keys-updated - The signal keys_updated is emitted when a DNSSEC key
set is updated; the signal parameter is zone name.

• ksk-submission The signal zone_ksk_submission is emitted if there is
a ready KSK present when the zone is signed; the signal parameters
are zone name, KSK keytag, and KSK KASP id.

• dnssec-invalid The signal zone_dnssec_invalid is emitted when DNSSEC
validation fails, or when ZONEMD verification fails; the signal para-
meters are 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
effect.

Default: none

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

Change of this parameter requires restart of the Knot server to take
effect.

Minimum: 0

Default: 1

listen
One or more IP addresses where the server listens for incoming queries.
Optional port specification (default is 53) can be appended to each ad-
dress using @ separator. Use 0.0.0.0 for all configured IPv4 addresses
or :: for all configured IPv6 addresses. Filesystem path can be speci-
fied for listening on local unix SOCK_STREAM socket. Non-absolute path
(i.e. not starting with /) is relative to rundir. Non-local address
binding is automatically enabled if supported by the operating system.

Change of this parameter requires restart of the Knot server to take
effect.

Default: not set

listen-quic
One or more IP addresses (and optionally ports) where the server lis-
tens for incoming queries over QUIC protocol.

Change of this parameter requires restart of the Knot server to take
effect.

Default: not set

listen-tls
One or more IP addresses (and optionally ports) where the server lis-
tens for incoming queries over TLS protocol (DoT).

Change of this parameter requires restart of the Knot server to take
effect.

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
ring-size: INT
busypoll-budget: INT
busypoll-timeout: INT

CAUTION:
When you change configuration parameters dynamically or via configu-
ration 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 de-
vice name, but the server will still listen on all addresses belonging
to the same interface! 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
effect.

CAUTION:
If XDP workers only process regular DNS traffic over UDP, it is
strongly recommended to also listen on the addresses which are in-
tended to offer the DNS service, at least to fulfil the DNS require-
ment 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
effect.

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
effect.

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
effect.

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
effect.

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 re-
ceived 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
before 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 inter-
face:

• 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. Pos-
sible VLAN tag is preserved.

Change of this parameter requires restart of the Knot server to take
effect.

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.forwarding=1). If forwarding is disabled, all in-
coming DNS packets are dropped!

Only VLAN 802.1Q is supported.

Default: off

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

Change of this parameter requires restart of the Knot server to take
effect.

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
effect.

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
effect.

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
effect.

Default: rundir/knot.sock

backlog
The control UNIX socket listen backlog size.

Change of this parameter requires restart of the Knot server to take
effect.

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
output, syslog (or systemd journal if systemd is enabled) or into an
arbitrary file.

There are 6 logging severity levels:

• critical Non-recoverable error resulting in server shutdown.

• error Recoverable error, action should be taken.

• warning Warning that might require user action.

• notice Server notice or hint.

• info Informational message.

• debug 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 Standard output.

• stderr Standard error output.

• syslog Syslog or systemd journal.

• file_name 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
catalog-db: str
catalog-db-max-size: SIZE
zone-db-listen: ADDR[@INT] | STR
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-absolute path is relative to the knotd startup directory.

Default: ${localstatedir}/lib/knot (configured with --with-stor-
age=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 perfor-
mance and durability.

Possible values:

• robust The journal database disk synchronization ensures database
durability but is generally slower.

• asynchronous 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: 500M (500 MiB)

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: 100M (100 MiB)

catalog-db
An explicit specification of the zone catalog database directory. Only
useful 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 IP address (and optionally a port) or a UNIX socket path of a run-
ning instance of a Redis (or compatible) database to be used for read-
ing and/or writing zone contents. See zone-db-input and zone-db-output.

Default: not set

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

Default: off

zone-db-cert-key
An ordered list of up to 4 public key PINs of the zone database's cer-
tificate. If the list is non-empty, communication with the zone data-
base is only possible over TLS, and a peer certificate is required. The
peer certificate'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
database's certificate. At least one hostname must match for the cer-
tificate 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 PEM files.

• pkcs11 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 sre stored in this keystore only if they are KSKs
or CSKs. Zone signing keys will be stored in subsequent keystore with-
out this option enabled.

Default: off

key-label
If enabled in combination with the PKCS #11 backend, generated keys are
labeled 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 un-
til the remote is reached.

Default: not set

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

via
An ordered list of source IP addresses which are used as source ad-
dresses 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 com-
munication 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 ob-
tained session tickets are used for reopening connections to re-
cently (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 communi-
cation 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 certifi-
cate. 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), sup-
press 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
subsequent AXFR/IXFR query do not share the same TCP connection. This
mode allows transfers from some broken DNS implementations (e.g.
ixfrdist).

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

Default: off

automatic-acl
If enabled, some authorized operations for the remote are automatically
allowed 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 configura-
tion.

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 no-
tification, and dynamic DNS update) which are allowed to be processed
or denied. Queries which don't require authorization are always al-
lowed.

id
An ACL rule identifier.

address
An ordered list of IP addresses, absolute UNIX socket paths, network
subnets, 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 re-
quired.

Default: not set

remote
An ordered list of references remote and remotes. The query must match
one of the remotes. Specifically, one of the remote's addresses and re-
mote's TSIG key if configured must match.

NOTE:
This option cannot be specified along with the address, key, or
protocol option at one ACL item.

Default: not set

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

Possible values:

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

• notify Allow incoming notify (NOTIFY).

• transfer Allow zone transfer (AXFR, IXFR).

• update Allow zone updates (DDNS).

Default: query

protocol
List of allowed protocols.

Possible values:

• udp UDP protocol.

• tcp TCP protocol.

• tls TLS protocol.

• quic QUIC protocol.

Default: not set (any)

deny
If enabled, instead of allowing, deny the matching combination of the
specified 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 up-
date 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 op-
tion.

Possible values:

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

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

• zone 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 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 The owner of each updated RR must be equal to at least one do-
main name set by update-owner.

• sub 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 The owner of each updated RR must match a pattern specified
by update-owner. The pattern can be an arbitrary FQDN or non-FQDN do-
main 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
submission. All of them must have a corresponding DS for the rollover
to continue. 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 par-
ents are configured. Set to 0 for infinity.

Default: 0

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

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 mas-
ter, 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
consistence 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 explic-
itly 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
management mode.

Default: off (module onlinesign has default on)

algorithm
An algorithm of signing keys and issued signatures. See DNSSEC Algo-
rithm 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 subse-
quent 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 Offline 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 gen-
erated, it is ensured that keytag % M == R. This prevents keytag con-
flict 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 fulfill the policy.

Default: 0/1

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

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 ini-
tiation.

NOTE:
More exactly, this period is measured since a ZSK is activated, and
after 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 resurrection is needed.

Default: 0

propagation-delay
An extra delay added for each key rollover step. This value (in sec-
onds) should be high enough to cover propagation of data from the pri-
mary server to all secondary servers, as well as the duration of sign-
ing routine itself and possible outages in signing and propagation in-
frastructure. 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
secondary 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-ex-
istence 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
signing.

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 updates 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 run-
ning, 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 syn-
chronization.

Default: not set

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

Possible values:

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

• delete-dnssec Publish special CDS and CDNSKEY records indicating
turning off DNSSEC.

• rollover Publish CDS and CDNSKEY records for ready and not yet ac-
tive KSK (submission phase of KSK rollover).

• always Always publish one CDS and one CDNSKEY records for the cur-
rent KSK.

• double-ds 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
handled when (re-)signing the zone.

Possible values:

• full 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 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, be-
longing 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 Nothing disabled.

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

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

• no-update-expired Don't update expired RRSIGs.

Multiple values may be specified.

WARNING:
This mode is intended for DNSSEC experts who understand the corre-
sponding 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 sec-
onds, it is considered failed.

Default: 300

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

Default: none

dump-removals
A path to file where the records being removed will be written before
waiting 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
identifier) can be used for global zone configuration or as an implicit
configuration 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 mod-
ule_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 rela-
tive to the knotd startup directory.

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

file
A path to the zone file. It is also possible to use the following for-
matters:

• %c[N] or %c[N-M] Means the Nth character or a sequence of characters
beginning from the Nth and ending with the Mth character of the tex-
tual 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] Means the Nth label of the textual zone name (see %s). The in-
dex is counted from 0 from the right (0 ~ TLD). If the label is not
available, the formatter has no effect.

• %s 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!).

• %% 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 con-
tents loaded from the database, however, zonefile-load: whole and
journal-content: 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 con-
tents. 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 sec-
ondary 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
delay 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 configured 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 specified amount of time (defined by this option in seconds),
change to the updated primary and force AXFR.

This option is useful when multiple primaries may have different zone
history 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 manda-
tory 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 up-
dates 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
mandatory 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 in-
stead.

Default: off

default-ttl
The default TTL value if none is specified in a zone file or zone in-
sertion 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 reloading or committing the configuration. Alternatively,
setting zonefile-load to difference-no-serial ensures the resulting
zone(s) update 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 ex-
pired (or after manual zone flush). This is applicable when the zone is
updated via IXFR, DDNS or automatic DNSSEC signing. In order to com-
pletely disable automatic zone file synchronization, set the value to
-1. In that case, it is still possible to force a manual zone flush us-
ing the -f option.

NOTE:
If you are serving large zones with frequent updates where the imme-
diate 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 The zone file is not used at all.

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

• difference-no-serial Same as difference, but the SOA serial in the
zone file is ignored, the server takes care of incrementing the ser-
ial automatically.

• whole 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
configuring 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 multi-
ple types may be specified. The special string dnssec represents all
types usually created by DNSSEC signing routines (DNSKEY, RRSIG, NSEC,
NSEC3, NSEC3PARAM, CDNSKEY, CDS 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 The journal is not used at all.

• changes Zone changes history is stored in journal.

• all Zone contents and history is stored in journal.

Default: changes

WARNING:
When this option is changed, the journal still contains data respec-
tive 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 consider 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 multi-
ple together. This preserves the complete history in the journal and
prevents the merging of changesets when multiple changesets are IXFRed
simultaneously. However, this does not prevent the merging (or dele-
tion) of old changesets in the journal to save space, as described in
journal behaviour.

This option leads to increased server load when processing IXFR, in-
cluding network traffic.

Default: off

ixfr-from-axfr
If a primary sends AXFR-style-IXFR upon an IXFR request, compute the
difference and process it as an incremental zone update (e.g. by stor-
ing 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. How-
ever the final size of the zone must satisfy the configured value.

Default: unlimited

adjust-threads
Parallelize internal zone adjusting procedures by using specified num-
ber of threads. This is useful with huge zones with NSEC3. Speedup ob-
servable 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
control socket 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 commit-
ted 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
emitted 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
(including NSEC/NSEC3 chain) with DNSSEC signatures every time the zone
is loaded or changed (including AXFR/IXFR).

When the validation fails, the zone being loaded or update being ap-
plied is cancelled with an error, and either none or previous zone
state is published.

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
emitted when the validation fails.

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
policy 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
emitted when the verification fails.

Default: off

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

Possible values:

• none No action regarding ZONEMD.

• zonemd-sha384 Generate ZONEMD using SHA384 algorithm.

• zonemd-sha512 Generate ZONEMD using SHA512 algorithm.

• remove Remove any ZONEMD from the zone apex.

Default: none

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

Possible values:

• increment The serial is incremented according to serial number
arithmetic.

• unixtime The serial is set to the current unix time.

• dateserial 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 in-
stead.

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 update 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
between 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 posi-
tive integers. Whenever the zone serial is incremented, it is ensured
that serial % M == R. This can be useful in the case of multiple incon-
sistent primaries, where distinct zone serial sequences prevent
cross-master-IXFR by any secondary.

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 ser-
ial. The shift is formatted as a signed integer, including the sign (+
or -). It is mostly useful with unixtime serial-policy, where the gen-
erated 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 automatically stored in the journal.

The auto-generated reverse zone is re-generated whenever any of the
specified 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 im-
plies ixfr-from-axfr: on and journal-content: all, otherwise
zonefile-load: difference-no-serial and journal-content: all.

Default: none

include-from
A list of subzones that should be flattened into this zone. The flat-
tening 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 im-
plies ixfr-from-axfr: on and journal-content: all, otherwise
zonefile-load: difference-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 pri-
mary 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 pri-
mary 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 Not a catalog zone.

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

• generate A catalog zone whose contents are generated according to
assigned member zones.

• member 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 cata-
log template.

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 and only if catalog-role is member.

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

Default: not set

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

NOTE:
This option has 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 mod-
ule_name or module_name/module_id. These modules apply only to the cur-
rent zone queries.

Default: not set

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

3.5.0 2025-09-18 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+15.0>

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