Provided by: knot_2.7.8-1_amd64 
NAME
knot.conf - Knot DNS configuration file
DESCRIPTION
Configuration files for Knot DNS use simplified YAML format. Simplified means that not all
of the features are supported.
For the description of configuration items, we have to declare a meaning of the following
symbols:
• INT – Integer
• STR – Textual string
• HEXSTR – Hexadecimal string (with 0x prefix)
• BOOL – Boolean value (on/off or true/false)
• TIME – Number of seconds, an integer with 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 activation and the next rollover initiation.
Default: 30 days
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.
ksk-lifetime
A period between KSK activation 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.
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 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-db-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 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 2010–2019, CZ.NIC, z.s.p.o.