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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 Two signals may be emitted: • started Emitted when the server is started and all configured zones (including catalog zones and their members) are loaded or successfully bootstrapped. • stopped Emitted when the server shutdown sequence is initiated. • zone-updated Two signals may be emitted: • zone_updated Emitted when a zone has been successfully updated. Parameters: zone name and zone SOA serial. • zone_not_updated Emitted when a zone has not been successfully up- dated. Parameters: zone name. • external-verify The signal external_verify is emitted when a zone is awaiting external validation before applying changes. Parameters: zone name and new zone SOA serial. • keys-updated The signal keys_updated is emitted when a DNSSEC key set is updated. Parameters: zone name. • ksk-submission The signal zone_ksk_submission is emitted if a ready KSK is present when the zone is signed. Parameters: zone name, KSK keytag, and KSK KASP id. • dnssec-invalid The signal zone_dnssec_invalid is emitted when DNSSEC validation fails or when ZONEMD verification fails. Parameters: zone name and remaining seconds until an RRSIG expires. NOTE: This function requires systemd version at least 221 or libdbus. TIP: A few sample script templates can be found in the project repository. Change of this parameter requires restart of the Knot server to take 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 (default is 853) 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 (default is 853) 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 zero-copy: 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 zero-copy If enabled and supported by the configured network device, zero-copy mode can be used. For testing purposes or if there is an issue with the kernel or device driver, disabling zero-copy may help, at the cost of lower performance. Change of this parameter requires restart of the Knot server to take effect. Default: on 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. 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 re- placement. Default: off DATABASE SECTION Configuration of databases for zone contents, DNSSEC metadata, or event timers. database: storage: STR journal-db: STR journal-db-mode: robust | asynchronous journal-db-max-size: SIZE kasp-db: STR kasp-db-max-size: SIZE timer-db: STR timer-db-max-size: SIZE timer-db-sync: never | shutdown | immediate | TIME catalog-db: str catalog-db-max-size: SIZE zone-db-listen: ADDR[@INT] | STR[@INT] ... zone-db-tls: BOOL zone-db-cert-key: BASE64 ... zone-db-cert-hostname: STR ... storage A data directory for storing journal, KASP, and timer databases. A non-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: 10G (10 GiB), or 512M (512 MiB) for 32-bit timer-db An explicit specification of the persistent timer database directory. Default: storage/timers timer-db-max-size The hard limit for the timer database maximum size. NOTE: This value also influences server's usage of virtual memory. Default: 5G (5 GiB), or 512M (512 MiB) for 32-bit timer-db-sync Specifies when zone timers should be written to the persistent timer database. Possible values: • never Never written. • shutdown Written once when the server is shut down. • immediate Each zone writes its timers whenever they are modified. This mode might slow down zones' events if many zones are configured. • INT A dedicated thread continuously iterates through the configured zones and writes their timers at the specified non-zero interval (in seconds). Default: shutdown 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 ordered list of IP addresses or hostnames, and optionally ports (de- fault is 6379), or absolute UNIX socket paths (starting with /) of run- ning Redis (or compatible) instances to be used for reading and/or writing zone contents. See zone-db-input and zone-db-output. The listen parameters are tried sequentially until a usable connection is established. The connected database can be a master, a replica, or a sentinel. If it is a sentinel, it is used to acquire connection para- meters of a master database. 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. 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: 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. acl: - id: STR address: ADDR[/INT] | ADDR-ADDR | STR ... key: key_id ... cert-key: BASE64 ... cert-hostname: STR ... 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 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 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. NOTE: This delay only affects automatic KSK submission with parent queries. For KSK submission resulting in timeout or manually con- firmed by knotc zone-ksk-submitted, the parent-delay doesn't apply. Default: 0 DNSKEY-SYNC SECTION Parameters of DNSKEY dynamic-update synchronization. dnskey-sync: - id: STR remote: remote_id | remotes_id ... check-interval: TIME id A dnskey-sync identifier. remote A list of references remote and remotes to other signers or common 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 catalog-role is member. The referenced catalog zone must exist and have catalog-role set to generate. WARNING: Atomically changing a member zone from one catalog zone to another that is consumed by the same secondary is not recommended, as the update to the target catalog zone may be randomly processed first and ignored due to a clash between catalogs. The correct catalog zone processing order on secondaries can be achieved by temporarily freezing outgoing transfers of the target catalog zone and thawing it after the source catalog zone has al- ready been processed (i.e. the member has been removed), and then manually notifying the secondaries. If the generated zone catalogs have already arrived at a secondary in the wrong order, triggering a zone retransfer of the target cata- log on the secondary fixes the situation. Default: not set catalog-group Assign this member zone to specified catalog group (configuration tem- plate). NOTE: This option has an effect if and only if catalog-role is member. Default: not set module An ordered list of references to query modules in the form of 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/> COPYRIGHT Copyright (C) CZ.NIC, z.s.p.o. and contributors 3.5.4 2026-04-02 KNOT.CONF(5)
NAME | DESCRIPTION | COMMENTS | INCLUDING CONFIGURATION | CLEARING CONFIGURATION SECTIONS | MODULE SECTION | SERVER SECTION | XDP SECTION | CONTROL SECTION | LOG SECTION | STATISTICS SECTION | DATABASE SECTION | KEYSTORE SECTION | KEY SECTION | REMOTE SECTION | REMOTES SECTION | ACL SECTION | SUBMISSION SECTION | DNSKEY-SYNC SECTION | POLICY SECTION | EXTERNAL SECTION | TEMPLATE SECTION | ZONE SECTION | AUTHOR | COPYRIGHT
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