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

    There are 12 main sections (module, server, control, log, statistics, keystore, policy, key, acl, remote, template, and zone) and module sections with the mod- prefix. Most of the sections (excluding server, control, and statistics) are sequences of settings blocks. Each settings block begins with a unique identifier, which can be used as a reference from other sections (such 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.

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

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

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-handshake-timeout: TIME
    tcp-idle-timeout: TIME
    tcp-reply-timeout: TIME
    max-tcp-clients: INT
    max-udp-payload: SIZE
    max-ipv4-udp-payload: SIZE
    max-ipv6-udp-payload: SIZE
    edns-client-subnet: BOOL
    answer-rotation: BOOL
    listen: ADDR[@INT] ...

  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 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 empty value to disable.

Default: server version

  nsid

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

Default: FQDN hostname

  rundir

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

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.

Default: root:root

  pidfile

A PID file location.

Default: rundir/knot.pid

  udp-workers

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

Default: auto-estimated optimal value based on the number of online CPUs

  tcp-workers

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

Default: auto-estimated optimal value based on the number of online CPUs

  background-workers

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

Default: auto-estimated optimal value based on the number of online CPUs

  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-handshake-timeout

Maximum time between newly accepted TCP connection and the first query. This is useful to disconnect inactive connections faster than connections that already made at least 1 meaningful query.

Default: 5

  tcp-idle-timeout

Maximum idle time between requests on a TCP connection. This also limits receiving of a single query, each query must be received in this time limit.

Default: 20

  tcp-reply-timeout

Maximum time to wait for an outgoing connection or for a reply to an issued request (SOA, NOTIFY, AXFR...).

Default: 10

  max-tcp-clients

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

Default: 100

  max-udp-payload

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

Default: 4096

  max-ipv4-udp-payload

Maximum EDNS0 UDP payload size for IPv4.

Default: 4096

  max-ipv6-udp-payload

Maximum EDNS0 UDP payload size for IPv6.

Default: 4096

  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.

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

  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

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 the control socket operations can take. Set 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

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 period, the KSK submission is automatically considered successful, even if all the checks were negative or no parents are configured. Set 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
    ksk-size: SIZE
    zsk-size: SIZE
    ksk-shared: BOOL
    dnskey-ttl: TIME
    zsk-lifetime: TIME
    ksk-lifetime: TIME
    propagation-delay: TIME
    rrsig-lifetime: TIME
    rrsig-refresh: TIME
    nsec3: BOOL
    nsec3-iterations: INT
    nsec3-opt-out: BOOL
    nsec3-salt-length: INT
    nsec3-salt-lifetime: TIME
    ksk-submission: submission_id
    cds-cdnskey-publish: none | delete-dnssec | rollover | always

  id

A policy identifier.

  keystore

A reference to a keystore holding private key material for zones. A special default value can be used for the default keystore settings.

Default: default

  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

    Default: ecdsap256sha256

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

  ksk-size

A length of newly generated KSK or CSK keys.

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

  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.

Default: zone SOA TTL

NOTE: Has infuence over ZSK key lifetime.

  zsk-lifetime

A period between ZSK publication and the next rollover initiation.

Default: 30 days

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

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

  ksk-lifetime

A period between KSK publication and the next rollover initiation.

Default: 0

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.

  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.

Default: 1 hour

NOTE: Has infuence over ZSK key lifetime.

  rrsig-lifetime

A validity period of newly issued signatures.

Default: 14 days

  rrsig-refresh

A period how long before a signature expiration the signature will be refreshed.

Default: 7 days

  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.

Default: 30 days

  ksk-submission

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

Default: not set

  cds-cdnskey-publish

Controls if and how shall the CDS and CDNSKEY be published in the zone.

NOTE: This only applies if the zone keys are automatically managed by the server.

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 CDS and CDNSKEY records for the current KSK.

    Default: always

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

  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 unless the operation is successful. Optional destination port (default is 53) can be appended to the address using @ separator.

Default: not set

  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

TEMPLATE SECTION

A template is a shareable zone setting which can be used for configuration of many zones in one place. A special default template (with the default identifier) can be used for global querying configuration or as an implicit configuration if a zone doesn't have another template specified.

template:
  - id: STR
    timer-db: STR
    max-timer-db-size: SIZE
    journal-db: STR
    journal-db-mode: robust | asynchronous
    max-journal-db-size: SIZE
    kasp-db: STR
    max-kasp-db-size: SIZE
    global-module: STR/STR ...
    # All zone options (excluding 'template' item)

  id

A template identifier.

  timer-db

Specifies a path of the persistent timer database. The path can be specified as a relative path to the default template storage.

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

Default: storage/timers

  max-timer-db-size

Hard limit for the timer database maximum size.

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

Default: 100 MiB

  journal-db

Specifies a path of the persistent journal database. The path can be specified as a relative path to the default template storage.

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

Default: storage/journal

  journal-db-mode

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

Possible values:

•   robust – The journal DB disk sychronization ensures DB durability but is generally slower.

•   asynchronous – The journal DB disk synchronization is optimized for better performance at the expense of lower DB durability; this mode is recommended only on slave nodes with many zones.

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

    Default: robust

  max-journal-db-size

Hard limit for the common journal DB. 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 lower than actual DB file size.

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

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

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

Default: 20 GiB (1 GiB for 32-bit)

  kasp-db

A KASP database path. Non-absolute path is relative to storage.

Default: storage/keys

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

  max-kasp-db-size

Hard limit for the KASP database maximum size.

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

Default: 500 MiB

  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
    max-journal-usage: SIZE
    max-journal-depth: INT
    max-zone-size : SIZE
    dnssec-signing: BOOL
    dnssec-policy: STR
    request-edns-option: INT:[HEXSTR]
    serial-policy: increment | unixtime | dateserial
    min-refresh-interval: TIME
    max-refresh-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, journal database, and timers database.

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

  file

A path to the zone file. Non-absolute path 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

  max-journal-usage

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

Default: 100 MiB

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

  max-journal-depth

Maximum history length of journal.

Minimum: 2

Default: 2^64

  max-zone-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. A special default value can be used for the default policy settings.

Required

  request-edns-option

An arbitrary EDNS0 option which is included into a server request (AXFR, IXFR, SOA, or NOTIFY). The value is in the option_code:option_data format.

Default: not set

  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

  min-refresh-interval

Forced minimum zone refresh interval to avoid flooding master.

Default: 2

  max-refresh-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 messages (must be turned on at compile time).

    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.

•   file_name – A specific file.

  server

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

Default: not set

  control

Minimum severity level for messages related to server control that are logged.

Default: not set

  zone

Minimum severity level for messages related to zones that are logged.

Default: not set

  any

Minimum severity level for all message types that are logged.

Default: not set

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

COPYRIGHT
Copyright 2010–2018, CZ.NIC, z.s.p.o.