Provided by: knot_3.4.3-1_amd64 
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 – 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 module sections. There
are 17 fixed sections (module, server, xdp, control, log, statistics, database, keystore,
key, remote, remotes, acl, submission, dnskey-sync, policy, 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 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 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 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 – 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 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 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
edns-client-subnet: BOOL
answer-rotation: BOOL
automatic-acl: BOOL
proxy-allowlist: ADDR[/INT] | ADDR-ADDR ...
dbus-event: none | running | zone-updated | 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 configuration file reload,
some parameters in the Server section require restarting 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-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 capabilities 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 connection. 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 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
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.
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_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 effect.
Minimum: 128
Default: 10000 (ten thousand)
quic-outbuf-max-size
Maximum cumulative size of memory used for buffers of unACKed sent messages. 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 expected.
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 connections 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 information 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 communication. 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
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 (including 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.
• 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;
the signal parameters are zone name, and remaining seconds until an RRSIG expires.
NOTE:
This function requires systemd version at least 221 or libdbus.
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 ensure 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 address using @ separator. Use
0.0.0.0 for all configured IPv4 addresses or :: for all configured IPv6 addresses.
Filesystem path can be specified 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 listens 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 listens 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 configuration 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 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 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 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 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 messages.
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 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 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 incoming 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.
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.
log:
- target: stdout | stderr | syslog | STR
server: critical | error | warning | notice | info | debug
control: critical | error | warning | notice | info | debug
zone: critical | error | warning | notice | info | debug
quic: critical | error | warning | notice | info | debug
any: critical | error | warning | notice | info | debug
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 replacement.
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
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-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 – 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
KEYSTORE SECTION
DNSSEC keystore configuration.
keystore:
- id: STR
backend: pem | pkcs11
config: STR
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
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.
key:
- id: DNAME
algorithm: hmac-md5 | hmac-sha1 | hmac-sha224 | hmac-sha256 | hmac-sha384 | hmac-sha512
secret: BASE64
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: not set
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 ...
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 communication 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 remote certificate public key PINs. If the list is non-empty,
communication with the remote is possible only via QUIC protocol 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 remains the same on a
certificate renewal.
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 implementations (e.g. Windows
Server 2016).
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 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 notification, and dynamic DNS
update) which are allowed to be processed or denied. Queries which don't require
authorization are always allowed.
acl:
- id: STR
address: ADDR[/INT] | ADDR-ADDR | STR ...
key: key_id ...
cert-key: BASE64 ...
remote: remote_id | remotes_id ...
action: query | notify | transfer | update ...
protocol: udp | tcp | tls | quic ...
deny: BOOL
update-type: STR ...
update-owner: key | zone | name
update-owner-match: sub-or-equal | equal | sub | pattern
update-owner-name: STR ...
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 possible only via QUIC protocol 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 remains the same on a
certificate renewal.
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 remote'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 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 — 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 domain 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 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 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 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 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 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 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.
Default: an imaginary keystore with all default values
NOTE:
A configured keystore called "default" won't be used unless explicitly referenced.
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 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 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 generated, 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 fulfill the policy.
Default: 0/1
ksk-lifetime
A period (in seconds) between KSK generation and the next rollover initiation.
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 initiation.
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 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 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-existence 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: 8
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 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 synchronization.
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 active KSK (submission
phase of KSK rollover).
• always – Always publish one CDS and one CDNSKEY records for the current 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.
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, 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 – 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 corresponding consequences.
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 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
master: remote_id | remotes_id ...
ddns-master: remote_id
notify: remote_id | remotes_id ...
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
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
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
reverse-generate: 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 formatters:
• %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 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] – 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 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
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 forwarded 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
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 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 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 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 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 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 possible 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 – 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 contents 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 serial 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.
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 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 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 multiple 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 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 difference 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 final 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)
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 applied 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.
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.
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 automatic 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 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 update per second per zone.
Generated catalog zones use unixtime only.
Default: increment (unixtime for generated catalog zones)
serial-modulo
Specifies that the zone serials 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 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 secondary.
NOTE:
In order to ensure the congruent policy, this option is only allowed with DNSSEC
signing enabled and zonefile-load to be either difference-no-serial or none.
Because the zone serial effectively always increments by M instead of 1, it is not
recommended to use dateserial serial-policy or even unixtime in case of rapidly updated
zone.
Default: 0/1
reverse-generate
This option triggers the automatic generation of reverse PTR records based on A/AAAA
records in the specified zone. The entire generated zone is automatically stored in the
journal.
Current limitations:
• Only one zone to be reversed can be specified.
• Is slow for large zones (even when changing a little).
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 – 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 catalog 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 template).
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 module_name or
module_name/module_id. These modules apply only to the current zone queries.
Default: not set
AUTHOR
CZ.NIC Labs <https://www.knot-dns.cz>
COPYRIGHT
Copyright 2010–2024, CZ.NIC, z.s.p.o.