Ubuntu Manpage: knot.conf - Knot DNS configuration file

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  15  fixed
       sections  (module,  server,  xdp,  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 " ".

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
tcp-fastopen: BOOL
remote-pool-limit: INT
remote-pool-timeout: TIME
remote-retry-delay: TIME
socket-affinity: BOOL
udp-max-payload: SIZE
udp-max-payload-ipv4: SIZE
udp-max-payload-ipv6: SIZE
edns-client-subnet: BOOL
answer-rotation: BOOL
dbus-event: none | running | zone-updated | ksk-submission | dnssec-invalid ...
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 that the changes 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 at the moment of the daemon start

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 employed
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

tcp-fastopen
If enabled, use TCP Fast Open for outbound TCP communication (client side): incoming zone transfers,
sending NOTIFY, and DDNS forwarding. This mode simplifies TCP handshake and can result in better
networking performance. TCP Fast Open for inbound TCP communication (server side) isn't affected by this
configuration as it's enabled automatically if supported by OS.

NOTE:
The TCP Fast Open support must also be enabled on the OS level:

• Linux/macOS: ensure kernel parameter net.ipv4.tcp_fastopen is 2 or 3 for server side, and 1 or 3 for
client side.

• FreeBSD: ensure kernel parameter net.inet.tcp.fastopen.server_enable is 1 for server side, and
net.inet.tcp.fastopen.client_enable is 1 for client side.

Default: off

remote-pool-limit
If nonzero, the server will keep up to this number of outgoing TCP connections open for later use. This
is an optimization to avoid frequent opening of TCP connections to the same remote.

Change of this parameter requires restart of the Knot server to take effect.

Default: 0

remote-pool-timeout
The timeout in seconds after which the unused kept-open outgoing TCP connections to remote servers are
closed.

Default: 5

remote-retry-delay
When a connection attempt times out to some remote address, this information will be kept for this
specified time (in milliseconds) and other connections to the same address won't be attempted. This
prevents repetitive waiting for timeout on an unreachable remote.

Default: 0

socket-affinity
If enabled and if SO_REUSEPORT is available on Linux, all configured network sockets are bound to UDP and
TCP workers in order to increase the networking performance. This mode isn't recommended for setups
where the number of network card queues is lower than the number of UDP or TCP workers.

Change of this parameter requires restart of the Knot server to take effect.

Default: off

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

NOTE:
It is advisable to adjust the maximum number of open files per process in your operating system
configuration.

Default: one half of the file descriptor limit for the server process

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

Default: 1232

udp-max-payload-ipv4
Maximum EDNS0 UDP payload size for IPv4.

Default: 1232

udp-max-payload-ipv6
Maximum EDNS0 UDP payload size for IPv6.

Default: 1232

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

dbus-event
Specification of server or zone states which emit a D-Bus signal on the system bus. The bus name is
cz.nic.knotd, the object path is /cz/nic/knotd, and the interface name is cz.nic.knotd.events.

Possible values:

• none – No signal is emitted.

• running – The signal started is emitted when the server is fully operational and the signal stopped is
emitted at the beginning of the server shutdown.

• zone-updated – The signal zone_updated is emitted when a zone has been updated; the signal parameters
are zone name and zone SOA serial.

• ksk-submission – The signal zone_ksk_submission is emitted if there is a ready KSK present when the
zone is signed; the signal parameters are zone name, KSK keytag, and KSK KASP id.

• dnssec-invalid – The signal zone_dnssec_invalid is emitted when DNSSEC validation fails; the signal
parameter is zone name.

NOTE:
This function requires systemd version at least 221.

Default: none

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. Filesystem path can be specified for listening on
local unix SOCK_STREAM socket. 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

XDP SECTION

Various options related to XDP listening, especially TCP.

xdp:
listen: STR[@INT] | ADDR[@INT] ...
tcp: BOOL
tcp-max-clients: INT
tcp-inbuf-max-size: SIZE
tcp-idle-close-timeout: TIME
tcp-idle-reset-timeout: TIME
route-check: BOOL

CAUTION:
When you change configuration parameters dynamically or via configuration file reload, some parameters
in the XDP section require restarting the Knot server so that the changes take effect.

listen
One or more network device names (e.g. ens786f0) on which the Mode XDP is enabled. Alternatively, an IP
address can be used instead of a 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.

CAUTION:
If XDP workers only process regular DNS traffic over UDP, it is strongly recommended to also listen on
the addresses which are intended to offer the DNS service, at least to fulfil the DNS requirement for
working TCP.

Default: not set

tcp
If enabled, DNS over TCP traffic is also processed with XDP workers.

The TCP stack features:

• Basic connection handling, sending/receiving data

• Close inactive connections

• Reset inactive connections which aren't able to close

• Reset invalid connections

• Ignore invalid resets and ACKs

• Receive fragmented data – one DNS message in multiple packets

• Limit total size of incoming buffers, reset most inactive connections with buffered data

• Send fragmented data – DNS message larger than allowed by MSS

• Send MSS option calculated from configured MSS and device MTU

• Receive and honor MSS option, limit the size of outgoing packet

• Send window size option (set to infinity)

Missing features:

• Receive and honor window size option, send only such amount of data at once, cache outgoing data

• Allow multi-message DNS responses (depends on above)

• Resend lost outgoing packets (not ACKed in time), including data

Change of this parameter requires restart of the Knot server to take effect.

WARNING:
This feature is experimental and it may eat your hamster as well as any other hamsters connected to
the network.

Default: off

tcp-max-clients
A maximum number of TCP clients connected in parallel.

Default: 1000000 (one million)

tcp-inbuf-max-size
Maximum cumulative size of memory used for buffers of incompletely received messages.

Minimum: 1 MiB

Default: 100 MiB

tcp-idle-close-timeout
Time in seconds, after which any idle connection is gracefully closed.

Minimum: 1 s

Default: 10 s

tcp-idle-reset-timeout
Time in seconds, after which any idle connection is forcibly closed.

Minimum: 1 s

Default: 20 s

route-check
If enabled, routing information from the operating system is considered when processing every incoming
DNS packet received over the XDP interface:

• If the outgoing interface of the corresponding DNS response differs from the incoming one, the packet
is processed normally by UDP/TCP workers (XDP isn't used).

• If the destination address is blackholed, unreachable, or prohibited, the DNS packet is dropped without
any response.

• The destination MAC address for the response is taken from the routing system.

If disabled, symmetrical routing is applied. It means that the query source MAC address is used as a
response destination MAC address.

Change of this parameter requires restart of the Knot server to take effect.

NOTE:
This mode requires forwarding enabled on the loopback interface (sysctl -w
net.ipv4.conf.lo.forwarding=1 and sysctl -w net.ipv6.conf.lo.forwarding=1). If forwarding is
disabled, all incoming DNS packets are dropped!

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

       Default: 5

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 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.

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

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
catalog-db: str
catalog-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 synchronization ensures database durability but is generally slower.

• asynchronous – The journal database disk synchronization is optimized for better performance at the
expense of lower database durability in the case of a crash. This mode is recommended on secondary
servers with many zones.

Default: robust

journal-db-max-size
The hard limit for the journal database maximum size. There is no cleanup logic in journal to recover
from reaching this limit. Journal simply starts refusing changes across all zones. Decreasing this value
has no effect if it is lower than the actual database file size.

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

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

Default: 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

catalog-db
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

catalog-db-max-size
The hard limit for the catalog database maximum size.

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

Default: 20 GiB (512 MiB for 32-bit)

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

KEY SECTION

       Shared TSIG keys used to authenticate communication with the server.

          key:
            - id: DNAME
              algorithm: hmac-md5 | hmac-sha1 | hmac-sha224 | hmac-sha256 | hmac-sha384 | hmac-sha512
              secret: BASE64

   id
       A key name identifier.

       NOTE:
          This  value  MUST  be  exactly  the same as the name of the TSIG key on the opposite primary/secondary
          server(s).

   algorithm
       A TSIG key algorithm. See TSIG Algorithm Numbers.

       Possible values:

       • hmac-md5

       • hmac-sha1

       • hmac-sha224

       • hmac-sha256

       • hmac-sha384

       • hmac-sha512

       Default: not set

   secret
       Shared key secret.

       Default: not set

REMOTE SECTION

Definitions of remote servers for outgoing connections (source of a zone transfer, target for a
notification, etc.).

remote:
- id: STR
address: ADDR[@INT] ...
via: ADDR[@INT] ...
key: key_id
block-notify-after-transfer: BOOL
no-edns: 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 as a source address for communication with the remote. This option can help if the server listens
on more addresses. Optional source port (default is random) can be appended to the address using @
separator.

Default: not set

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 primary server), suppress sending NOTIFY messages to all
configured secondary servers.

Default: off

no-edns
If enabled, no OPT record (EDNS) is inserted to outgoing requests to this remote server. This mode is
necessary for communication with some broken implementations (e.g. Windows Server 2016).

Default: off

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.).

id
An ACL rule identifier.

address
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

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

remote
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:
This option cannot be specified along with the address or key option at one ACL item.

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. Every listed owner
name which is not FQDN (i.e. it doesn't end in a dot) is considered as if it was appended with the target
zone name. Such a relative owner name specification allows better ACL rule reusability across multiple
zones.

Default: not set

SUBMISSION SECTION

       Parameters of KSK submission checks.

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

   parent-delay
       After  successful  parent  DS  check, wait for this period before continuing the next key roll-over step.
       This delay shall cover the propagation delay of update in the parent zone.

       Default: 0

POLICY SECTION

DNSSEC policy configuration.

policy:
- id: STR
keystore: keystore_id
manual: BOOL
single-type-signing: BOOL
algorithm: rsasha1 | rsasha1-nsec3-sha1 | rsasha256 | rsasha512 | ecdsap256sha256 | ecdsap384sha384 | ed25519 | ed448
ksk-size: SIZE
zsk-size: SIZE
ksk-shared: BOOL
dnskey-ttl: TIME
zone-max-ttl: TIME
ksk-lifetime: TIME
zsk-lifetime: TIME
delete-delay: TIME
propagation-delay: TIME
rrsig-lifetime: TIME
rrsig-refresh: TIME
rrsig-pre-refresh: TIME
reproducible-signing: BOOL
nsec3: BOOL
nsec3-iterations: INT
nsec3-opt-out: BOOL
nsec3-salt-length: INT
nsec3-salt-lifetime: TIME
signing-threads: INT
ksk-submission: submission_id
ds-push: remote_id
cds-cdnskey-publish: none | delete-dnssec | rollover | always | double-ds
cds-digest-type: sha256 | sha384
offline-ksk: BOOL
unsafe-operation: none | no-check-keyset | no-update-dnskey | no-update-nsec | no-update-expired ...

id
A policy identifier.

keystore
A reference to a keystore holding private key material for zones.

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 (module onlinesign has default on)

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 or more KSKs. More KSKs can be shared
during a KSK rollover.

WARNING:
As the shared KSK set is bound to the policy id, renaming the policy breaks this connection and new
shared KSK set is initiated when a new KSK is needed.

Default: off

dnskey-ttl
A TTL value for DNSKEY records added into zone apex.

NOTE:
Has influence over ZSK key lifetime.

WARNING:
Ensure all DNSKEYs with updated TTL are propagated before any 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

ksk-lifetime
A period between KSK activation and the next rollover initiation.

NOTE:
KSK key lifetime is also influenced by propagation-delay, dnskey-ttl, and KSK submission delay.

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

This applies for CSK lifetime if single-type-signing is enabled.

Default: 0

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 influenced by propagation-delay and dnskey-ttl

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

Default: 30 days

delete-delay
Once a key (KSK or ZSK) is rolled-over and removed from the zone, keep it in the KASP database for at
least this period before deleting it completely. This might be useful in some troubleshooting cases when
resurrection is needed.

Default: 0

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

NOTE:
Has influence 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 secondary servers 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

reproducible-signing
For ECDSA algorithms, generate RRSIG signatures deterministically (RFC 6979). Besides better theoretical
cryptographic security, this mode allows significant speed-up of loading signed (by the same method)
zones. However, the zone signing is a bit slower.

Default: off

nsec3
Specifies if NSEC3 will be used instead of NSEC.

Default: off

nsec3-iterations
A number of additional times the hashing is performed.

Default: 10

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

signing-threads
When signing zone or update, use this number of threads for parallel signing.

Those are extra threads independent of Background workers.

NOTE:
Some steps of the DNSSEC signing operation are not parallelized.

Default: 1 (no extra threads)

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

Default: not set

ds-push
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

cds-cdnskey-publish
Controls if and how shall the CDS and CDNSKEY be published in the zone.

Possible values:

• none – Never publish any CDS or CDNSKEY records in the zone.

• delete-dnssec – Publish special CDS and CDNSKEY records indicating turning off DNSSEC.

• rollover – Publish CDS and CDNSKEY records for ready and not yet active KSK (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

cds-digest-type
Specify digest type for published CDS records.

Default: sha256

offline-ksk
Specifies if Offline KSK feature is enabled.

Default: off

unsafe-operation
Turn off some DNSSEC safety features.

Possible values:

• none – Nothing disabled.

• no-check-keyset – Don't check active keys in present algorithms. This may lead to violation of RFC
4035#section-2.2.

• no-update-dnskey – Don't maintain/update DNSKEY, CDNSKEY, and CDS records in the zone apex according to
KASP database. Juste leave them as they are in the zone.

• no-update-nsec – Don't maintain/update NSEC/NSEC3 chain. Leave all the records as they are in the zone.

• no-update-expired – Don't update expired RRSIGs.

Multiple values may be specified.

WARNING:
This mode is intended for DNSSEC experts who understand the corresponding consequences.

Default: none

TEMPLATE SECTION

       A template is shareable zone settings, which can simplify configuration by reducing duplicates. A special
       default  template  (with  the  default  identifier)  can  be  used for global zone configuration or as an
       implicit configuration if a zone doesn't have another template specified.

          template:
            - id: STR
              global-module: STR/STR ...
              # All zone options (excluding 'template' item)

   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
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: policy_id
zonemd-verify: BOOL
zonemd-generate: none | zonemd-sha384 | zonemd-sha512 | remove
serial-policy: increment | unixtime | dateserial
refresh-min-interval: TIME
refresh-max-interval: TIME
catalog-role: none | interpret | generate | member
catalog-template: template_id ...
catalog-zone: DNAME
catalog-group: STR
module: STR/STR ...

domain
A zone name identifier.

template
A reference to a configuration template.

Default: not set or default (if the template exists)

storage
A data directory for storing zone files.

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 primary servers (formerly known as master servers).

Default: not set

ddns-master
A reference to zone primary master. 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

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 and no zone contents in the
journal), it behaves the same way as 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 the journal.

NOTE:
Zone-in-journal changeset isn't counted to the limit.

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

adjust-threads
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

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

Default: off

dnssec-validation
If enabled, the zone contents are validated for being correctly signed (including NSEC/NSEC3 chain) with
DNSSEC signatures every time the zone is loaded or changed (including AXFR/IXFR).

When the validation fails, the zone being loaded or update being applied is cancelled with an error, and
either none or previous zone state is published.

List of DNSSEC checks:

• Every zone RRSet is correctly signed by at least one present DNSKEY.

• DNSKEY RRSet is signed by KSK.

• NSEC(3) RR exists for each name (unless opt-out) with correct bitmap.

• Every NSEC(3) RR is linked to the lexicographically next one.

The validation is not affected by dnssec-policy configuration, except for signing-threads option, which
specifies the number of threads for parallel validation.

NOTE:
Redundant or garbage NSEC3 records are ignored.

This mode is not compatible with dnssec-signing.

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.

zonemd-verify
On each zone load/update, verify that ZONEMD is present in the zone and valid.

NOTE:
Zone digest calculation may take much time and CPU on large zones.

Default: off

zonemd-generate
On each zone update, calculate ZONEMD and put it into the zone.

Possible values:

• none – No action regarding ZONEMD.

• zonemd-sha384 – Generate ZONEMD using SHA384 algorithm.

• zonemd-sha512 – Generate ZONEMD using SHA512 algorithm.

• remove – Remove any ZONEMD from the zone apex.

Default: none

serial-policy
Specifies how the zone serial is updated after a dynamic update or 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:
If the resulting serial for unixtime or dateserial is lower or equal than the current serial (this
happens e.g. when migrating from other policy or frequent updates), the serial is incremented instead.

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

refresh-min-interval
Forced minimum zone refresh interval to avoid flooding primary server.

Default: 2

refresh-max-interval
Forced maximum zone refresh interval.

Default: not set

catalog-role
Trigger zone catalog feature. Possible values:

• none – Not a catalog zone.

• interpret – A catalog zone which is loaded from a zone file or XFR, and member zones shall be
configured based on its contents.

• generate – A catalog zone whose contents are generated according to assigned member zones.

• member – A member zone that is assigned to one generated catalog zone.

Default: none

catalog-template
For the catalog member zones, the specified configuration template will be applied.

Multiple catalog templates may be defined. The first one is used unless the member zone has the group
property defined, matching another catalog template.

NOTE:
This option must be set if and only if catalog-role is interpret.

Default: not set

catalog-zone
Assign this member zone to specified generated catalog zone.

NOTE:
This option must be set if and only if catalog-role is member.

The referenced catalog zone must exist and have catalog-role set to generate.

Default: not set

catalog-group
Assign this member zone to specified catalog group (configuration template).

NOTE:
This option has effect if and only if catalog-role is member.

Default: not set

module
An ordered list of references to query modules in the form of module_name or module_name/module_id. These
modules apply only to the current zone queries.

Default: not set

AUTHOR

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

COPYRIGHT

       Copyright 2010–2022, CZ.NIC, z.s.p.o.

3.1.6                                              2022-02-08                                       KNOT.CONF(5)