KNOT.CONF(5)

NAME
knot.conf - Knot DNS configuration file

DESCRIPTION

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

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

•   INT – 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 possible time multiplier suffix (s ~ 1, m ~ 60, h ~ 3600 or d ~ 24 * 3600)

•   SIZE – Number of bytes, an integer with 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 14 fixed sections (module, server, key, acl, control, statistics, database, keystore, submission, policy, remote, template, zone, log). 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 value within double quotes " ".

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.

INCLUDES

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

include: STR

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
    udp-max-payload: SIZE
    udp-max-payload-ipv4: SIZE
    udp-max-payload-ipv6: SIZE
    edns-client-subnet: BOOL
    answer-rotation: BOOL
    listen: 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 as the change 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

  rundir

A path for storing run-time data (PID file, unix sockets, etc.).

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 s

Default: 10 s

  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 ms

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 ms

  tcp-reuseport

If enabled, each TCP worker listens on its own socket and the OS kernel socket load balancing is emloyed 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 slave servers.

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

  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

  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. 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

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 master/slave 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

ACL SECTION

Access control list rule definitions. The ACLs are used to match incoming connections to allow or deny requested operation (zone transfer request, DDNS update, etc.).

acl:
  - id: STR
    address: ADDR[/INT] | ADDR-ADDR ...
    key: key_id ...
    action: notify | transfer | update ...
    deny: BOOL
    update-type: STR ...
    update-owner: key | zone | name
    update-owner-match: sub-or-equal | equal | sub
    update-owner-name: STR ...

  id

An ACL rule identifier.

  address

An ordered list of IP addresses, network subnets, or network ranges. The query must match one of them. Empty value means that address match is not required.

Default: not set

  key

An ordered list of references to TSIG keys. The query must match one of them. Empty value means that transaction authentication is not used.

Default: not set

  action

An ordered list of allowed (or denied) actions.

Possible values:

•   notify – Allow incoming notify.

•   transfer – Allow zone transfer.

•   update – Allow zone updates.

    Default: not set

  deny

If enabled, instead of allowing, deny the specified action, address, key, or combination if these items. If no action is specified, deny all actions.

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 Resource Record in an update must either be equal to or be a subdomain of at least one domain set by update-owner.

•   equal — The owner of each updated RR must be equal to at least one domain 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 set by update-owner.

    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.

Default: not set

CONTROL SECTION

Configuration of the server control interface.

control:
    listen: STR
    timeout: TIME

  listen

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

Default: rundir/knot.sock

  timeout

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

Default: 5

STATISTICS SECTION

Periodic server statistics dumping.

statistics:
    timer: TIME
    file: STR
    append: BOOL

  timer

A period 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

  storage

A data directory for storing journal, KASP, and timer databases.

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

  journal-db

An explicit specification of the persistent journal database directory. Non-absolute path (i.e. not starting with /) is relative to storage.

Default: storage/journal

  journal-db-mode

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

Possible values:

•   robust – The journal database disk sychronization 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 slave nodes 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: 20 GiB (512 MiB for 32-bit)

  kasp-db

An explicit specification of the KASP database directory. Non-absolute path (i.e. not starting with /) is relative to storage.

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: 500 MiB

  timer-db

An explicit specification of the persistent timer database directory. Non-absolute path (i.e. not starting with /) is relative to storage.

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: 100 MiB

KEYSTORE SECTION

DNSSEC keystore configuration.

keystore:
  - id: STR
    backend: pem | pkcs11
    config: STR

  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-url> <module-path>).

NOTE: Example configuration string for PKCS #11:

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

Default: kasp-db/keys

SUBMISSION SECTION

Parameters of KSK submission checks.

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

  id

A submission identifier.

  parent

A list of references 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 for periodic checks of DS presence on parent's DNS servers, in the case of the KSK submission.

Default: 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

POLICY SECTION

DNSSEC policy configuration.

policy:
  - id: STR
    keystore: STR
    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
    zsk-lifetime: TIME
    ksk-lifetime: TIME
    propagation-delay: TIME
    rrsig-lifetime: TIME
    rrsig-refresh: TIME
    rrsig-pre-refresh: TIME
    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
    cds-cdnskey-publish: none | delete-dnssec | rollover | always | double-ds
    offline-ksk: BOOL

  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

  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: Ed25519 algorithm is only available if compiled with GnuTLS 3.6.0+.

    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 KSK.

Default: off

  dnskey-ttl

A TTL value for DNSKEY records added into zone apex.

NOTE: Has infuence 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

  zsk-lifetime

A period 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.

ZSK key lifetime is also infuenced by propagation-delay and dnskey-ttl

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

Default: 30 days

  ksk-lifetime

A period between KSK activation and the next rollover initiation.

NOTE: KSK key lifetime is also infuenced 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

  propagation-delay

An extra delay added for each key rollover step. This value should be high enough to cover propagation of data from the master server to all slaves.

NOTE: Has infuence over ZSK key lifetime.

Default: 1 hour

  rrsig-lifetime

A validity period 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: 14 days

  rrsig-refresh

A period how long at least before a signature expiration the signature will be refreshed, in order to prevent expired RRSIGs on slaves or resolvers' caches.

Default: 7 days

  rrsig-pre-refresh

A period 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: 1 hour

  nsec3

Specifies if NSEC3 will be used instead of NSEC.

Default: off

  nsec3-iterations

A number of additional times the hashing is performed.

Default: 5

  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 of newly issued salt field.

Zero value means infinity.

Default: 30 days

  ksk-submission

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

Default: not set

  ds-push

An optional reference 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: Module Onlinesign doesn't support DS push.

Default: not set

  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)

  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 only in the 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.

    Default: rollover

  offline-ksk

Specifies if Offline KSK feature is enabled.

Default: off

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] ...
    via: ADDR[@INT] ...
    key: key_id
    block-notify-after-transfer: BOOL

  id

A remote identifier.

  address

An ordered list of destination IP addresses which are used for communication with the remote server. The addresses are tried in sequence until the remote is reached. Optional destination port (default is 53) can be appended to the address using @ separator.

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. The first address with the same family as the destination address is used. Optional source port (default is random) can be appended to the address using @ separator.

Default: not set

  key

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

Default: not set

  block-notify-after-transfer

When incoming AXFR/IXFR from this remote (as a master), suppress sending NOTIFY messages to all configured slaves.

Default: off

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)

  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 ...
    ddns-master: remote_id
    notify: remote_id ...
    acl: acl_id ...
    semantic-checks: BOOL
    disable-any: BOOL
    zonefile-sync: TIME
    zonefile-load: none | difference | difference-no-serial | whole
    journal-content: none | changes | all
    journal-max-usage: SIZE
    journal-max-depth: INT
    zone-max-size : SIZE
    dnssec-signing: BOOL
    dnssec-policy: STR
    serial-policy: increment | unixtime | dateserial
    refresh-min-interval: TIME
    refresh-max-interval: TIME
    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.

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

  file

A path to the zone file. Non-absolute path (i.e. not starting with /) is relative to storage. 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 to zone master servers.

Default: not set

  ddns-master

A reference to zone primary master server. If not specified, the first master server is used.

Default: not set

  notify

An ordered list of references to remotes to which notify message is sent if the zone changes.

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

  semantic-checks

If enabled, extra zone semantic checks are turned on.

Several checks are enabled by default and cannot be turned off. An error in mandatory checks causes zone not to be loaded. An error in extra checks is logged only.

Mandatory checks:

•   SOA record missing in the zone (RFC 1034)

•   An extra record together with CNAME record except for RRSIG and DS (RFC 1034)

•   Multiple CNAME record with the same owner

•   DNAME record having a record under it (RFC 2672)

    Extra checks:

•   Missing NS record at the zone apex

•   Missing glue A or AAAA record

•   Invalid DNSKEY, DS, or NSEC3PARAM record

•   CDS or CDNSKEY inconsistency

•   Missing, invalid, or unverifiable RRSIG record

•   Invalid NSEC(3) record

•   Broken or non-cyclic NSEC(3) chain

    Default: off

  disable-any

If enabled, all authoritative ANY queries sent over UDP will be answered with an empty response and with the TC bit set. Use this option to minimize the risk of DNS reflection attack.

Default: off

  zonefile-sync

The time 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 of Knot and no zone contents in journal), it behaves the same way like whole.

    Default: whole

  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

  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: 100 MiB

  journal-max-depth

Maximum history length of journal.

Minimum: 2

Default: 2^64

  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: 2^64

  dnssec-signing

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

Default: off

  dnssec-policy

A reference to DNSSEC signing policy.

Default: an imaginary policy with all default values

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

  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: In case of unixtime, if the resulting serial is lower or equal than current zone (this happens e.g. in case of migrating from other policy or frequent updates) the serial is incremented instead.

    Use dateserial only if you expect less than 100 updates per day per zone.

    Default: increment

  refresh-min-interval

Forced minimum zone refresh interval to avoid flooding master.

Default: 2

  refresh-max-interval

Forced maximum zone refresh interval.

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

LOGGING 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 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
        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.

  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

  any

Minimum severity level for all message types to be logged.

Default: not set

AUTHOR
CZ.NIC Labs <https://www.knot-dns.cz>

COPYRIGHT
Copyright 2010–2020, CZ.NIC, z.s.p.o.