| KNOT.CONF(5) | Knot DNS | KNOT.CONF(5) |
knot.conf - Knot DNS configuration file
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:
The configuration consists of several fixed sections and optional module sections. There are 14 fixed sections (module, server, control, log, statistics, database, keystore, key, remote, acl, submission, policy, template, zone). Module sections are prefixed with the mod- prefix (e.g. mod-stats).
Most of the sections (e.g. zone) are sequences of settings blocks. Each settings block begins with a unique identifier, which can be used as a reference from other sections (such an identifier must be defined in advance).
A multi-valued item can be specified either as a YAML sequence:
address: [10.0.0.1, 10.0.0.2]
or as more single-valued items each on an extra line:
address: 10.0.0.1 address: 10.0.0.2
If an item value contains spaces or other special characters, it is necessary to enclose such a value within double quotes " ".
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.
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
Dynamic modules loading configuration.
NOTE:
module:
- id: STR
file: STR
A module identifier in the form of the mod- prefix and module name suffix.
A path to a shared library file with the module implementation.
WARNING:
Default: ${libdir}/knot/modules-${version}/module_name.so (or ${path}/module_name.so if configured with --with-moduledir=path)
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
socket-affinity: 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] ...
listen-xdp: STR[@INT] | ADDR[@INT] ...
CAUTION:
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
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
A DNS name server identifier (RFC 5001). Set to an empty value to disable.
Default: FQDN hostname
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)
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
A PID file location.
Change of this parameter requires restart of the Knot server to take effect.
Default: rundir/knot.pid
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
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
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
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
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
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:
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
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 secondary servers.
Change of this parameter requires restart of the Knot server to take effect.
Default: off
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
A maximum number of TCP clients connected in parallel, set this below the file descriptor limit to avoid resource exhaustion.
NOTE:
Default: one half of the file descriptor limit for the server process
Maximum EDNS0 UDP payload size default for both IPv4 and IPv6.
Default: 1232
Maximum EDNS0 UDP payload size for IPv4.
Default: 1232
Maximum EDNS0 UDP payload size for IPv6.
Default: 1232
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
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
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
One or more network device names (e.g. ens786f0) on which the Mode XDP is enabled. Alternatively, an IP address can be used instead of a device name, but the server will still listen on all addresses belonging to the same interface! Optional port specification (default is 53) can be appended to each device name or address using @ separator.
Change of this parameter requires restart of the Knot server to take effect.
Default: not set
CAUTION:
Configuration of the server control interface.
control:
listen: STR
timeout: TIME
A UNIX socket path where the server listens for control commands.
Default: rundir/knot.sock
Maximum time (in seconds) the control socket operations can take. Set to 0 for infinity.
Default: 5
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:
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
any: critical | error | warning | notice | info | debug
A logging output.
Possible values:
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.
Minimum severity level for messages related to general operation of the server to be logged.
Default: not set
Minimum severity level for messages related to server control to be logged.
Default: not set
Minimum severity level for messages related to zones to be logged.
Default: not set
Minimum severity level for all message types to be logged.
Default: not set
Periodic server statistics dumping.
statistics:
timer: TIME
file: STR
append: BOOL
A period after which all available statistics metrics will by written to the file.
Default: not set
A file path of statistics output in the YAML format.
Default: rundir/stats.yaml
If enabled, the output will be appended to the file instead of file replacement.
Default: off
Configuration of databases for zone contents, DNSSEC metadata, or event timers.
database:
storage: STR
journal-db: STR
journal-db-mode: robust | asynchronous
journal-db-max-size: SIZE
kasp-db: STR
kasp-db-max-size: SIZE
timer-db: STR
timer-db-max-size: SIZE
catalog-db: str
catalog-db-max-size: SIZE
A data directory for storing journal, KASP, and timer databases.
Default: ${localstatedir}/lib/knot (configured with --with-storage=path)
An explicit specification of the persistent journal database directory. Non-absolute path (i.e. not starting with /) is relative to storage.
Default: storage/journal
Specifies journal LMDB backend configuration, which influences performance and durability.
Possible values:
Default: robust
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:
Default: 20 GiB (512 MiB for 32-bit)
An explicit specification of the KASP database directory. Non-absolute path (i.e. not starting with /) is relative to storage.
Default: storage/keys
The hard limit for the KASP database maximum size.
NOTE:
Default: 500 MiB
An explicit specification of the persistent timer database directory. Non-absolute path (i.e. not starting with /) is relative to storage.
Default: storage/timers
The hard limit for the timer database maximum size.
NOTE:
Default: 100 MiB
An explicit specification of the zone catalog database directory. Only useful if catalog-zones are enabled. Non-absolute path (i.e. not starting with /) is relative to storage.
Default: storage/catalog
The hard limit for the catalog database maximum size.
NOTE:
Default: 20 GiB (512 MiB for 32-bit)
DNSSEC keystore configuration.
keystore:
- id: STR
backend: pem | pkcs11
config: STR
A keystore identifier.
A key storage backend type.
Possible values:
Default: pem
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:
"pkcs11:token=knot;pin-value=1234 /usr/lib64/pkcs11/libsofthsm2.so"
Default: kasp-db/keys
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
A key name identifier.
NOTE:
A TSIG key algorithm. See TSIG Algorithm Numbers.
Possible values:
Default: not set
Shared key secret.
Default: not set
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
A remote identifier.
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:
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
A reference to the TSIG key which is used to authenticate the communication with the remote server.
Default: not set
When incoming AXFR/IXFR from this remote (as a primary server), suppress sending NOTIFY messages to all configured secondary servers.
Default: off
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 ...
remote: remote_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 ...
An ACL rule identifier.
An ordered list of IP addresses, network subnets, or network ranges. The query's source address must match one of them. Empty value means that address match is not required.
Default: not set
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
An ordered list of references to remotes. The query must match one of the remotes. Specifically, one of the remote's addresses and remote's TSIG key if configured must match.
NOTE:
Default: not set
An ordered list of allowed (or denied) actions.
Possible values:
Default: not set
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
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
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:
Default: not set
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:
Default: sub-or-equal
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
Parameters of KSK submission checks.
submission:
- id: STR
parent: remote_id ...
check-interval: TIME
timeout: TIME
A submission identifier.
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:
Interval for periodic checks of DS presence on parent's DNS servers, in the case of the KSK submission.
Default: 1 hour
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
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
ksk-lifetime: TIME
zsk-lifetime: 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
cds-cdnskey-publish: none | delete-dnssec | rollover | always | double-ds
offline-ksk: BOOL
A policy identifier.
A reference to a keystore holding private key material for zones.
Default: an imaginary keystore with all default values
NOTE:
If enabled, automatic key management is not used.
Default: off
If enabled, Single-Type Signing Scheme is used in the automatic key management mode.
Default: off (module onlinesign has default on)
An algorithm of signing keys and issued signatures. See DNSSEC Algorithm Numbers.
Possible values:
NOTE:
Ed448 algorithm is only available if compiled with GnuTLS 3.6.12+ and Nettle 3.6+.
Default: ecdsap256sha256
A length of newly generated KSK or CSK keys.
Default: 2048 (rsa*), 256 (ecdsap256), 384 (ecdsap384), 256 (ed25519), 456 (ed448)
A length of newly generated ZSK keys.
Default: see default for ksk-size
If enabled, all zones with this policy assigned will share one KSK.
Default: off
A TTL value for DNSKEY records added into zone apex.
NOTE:
WARNING:
Default: zone SOA TTL
Declare (override) maximal TTL value among all the records in zone.
NOTE:
Default: computed after zone is loaded
A period between KSK activation and the next rollover initiation.
NOTE:
Zero (aka infinity) value causes no KSK rollover as a result.
This applies for CSK lifetime if single-type-signing is enabled.
Default: 0
A period between ZSK activation and the next rollover initiation.
NOTE:
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
An extra delay added for each key rollover step. This value should be high enough to cover propagation of data from the primary server to all secondary servers.
NOTE:
Default: 1 hour
A validity period of newly issued signatures.
NOTE:
Default: 14 days
A period 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: 7 days
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
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
Specifies if NSEC3 will be used instead of NSEC.
Default: off
A number of additional times the hashing is performed.
Default: 5
If set, NSEC3 records won't be created for insecure delegations. This speeds up the zone signing and reduces overall zone size.
WARNING:
Default: off
A length of a salt field in octets, which is appended to the original owner name before hashing.
Default: 8
A validity period of newly issued salt field.
Zero value means infinity.
Default: 30 days
When signing zone or update, use this number of threads for parallel signing.
Those are extra threads independent of Background workers.
NOTE:
Default: 1 (no extra threads)
A reference to submission section holding parameters of KSK submission checks.
Default: not set
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:
NOTE:
Default: not set
Controls if and how shall the CDS and CDNSKEY be published in the zone.
Possible values:
NOTE:
Default: rollover
Specifies if Offline KSK feature is enabled.
Default: off
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)
A template identifier.
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:
Default: not set
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
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
adjust-threads: INT
dnssec-signing: BOOL
dnssec-validation: BOOL
dnssec-policy: STR
serial-policy: increment | unixtime | dateserial
refresh-min-interval: TIME
refresh-max-interval: TIME
catalog-role: none | interpret
catalog-template: template_id
module: STR/STR ...
A zone name identifier.
A reference to a configuration template.
Default: not set or default (if the template exists)
A data directory for storing zone files.
Default: ${localstatedir}/lib/knot (configured with --with-storage=path)
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:
WARNING:
Default: storage/%s.zone
An ordered list of references to zone primary servers (formerly known as master servers).
Default: not set
A reference to zone primary master. If not specified, the first master server is used.
Default: not set
An ordered list of references to remotes to which notify message is sent if the zone changes.
Default: not set
An ordered list of references to ACL rules which can allow or disallow zone transfers, updates or incoming notifies.
Default: not set
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:
Extra checks:
Default: off
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:
Default: 0 (immediate)
Selects how the zone file contents are applied during zone load.
Possible values:
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
Selects how the journal shall be used to store zone and its changes.
Possible values:
Default: changes
Policy how much space in journal DB will the zone's journal occupy.
NOTE:
Default: 100 MiB
Maximum history length of journal.
Minimum: 2
Default: 2^64
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
Parallelize internal zone adjusting procedures. This is useful with huge zones with NSEC3. Speedup observable at server startup and while processing NSEC3 re-salt.
Default: 1
If enabled, automatic DNSSEC signing for the zone is turned on.
Default: off
If enabled, the zone contents are validated for being correctly signed (including NSEC/NSEC3 chain) with DNSSEC signatures every time the zone is loaded or changed (including AXFR/IXFR).
When the validation fails, the zone being loaded or update being applied is cancelled with an error, and either none or previous zone state is published.
List of DNSSEC checks:
The validation is not affected by dnssec-policy configuration, except for signing-threads option, which specifies the number of threads for parallel validation.
NOTE:
This mode is not compatible with dnssec-signing.
A reference to DNSSEC signing policy.
Default: an imaginary policy with all default values
NOTE:
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:
NOTE:
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.
Default: increment
Forced minimum zone refresh interval to avoid flooding primary server.
Default: 2
Forced maximum zone refresh interval.
Default: not set
Trigger zone catalog feature. Possible values:
Default: none
For the catalog-member zones, the specified configuration template will be applied.
NOTE:
Default: not set
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
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| 2021-03-25 | 3.0.5 |