knot.conf(5)
NAME
knot.conf - Knot DNS configuration file
DESCRIPTION
Configuration files for Knot DNS use simplified YAML format. Simplified
means that not all of the features are supported.
For the description of configuration items, we have to declare a
meaning of the following symbols:
* INT -- Integer
* STR -- Textual string
* HEXSTR -- Hexadecimal string (with 0x prefix)
* BOOL -- Boolean value (on/off or true/false)
* TIME -- Number of seconds, an integer with possible time multiplier
suffix (s ~ 1, m ~ 60, h ~ 3600 or d ~ 24 * 3600)
* SIZE -- Number of bytes, an integer with possible size multiplier
suffix (B ~ 1, K ~ 1024, M ~ 1024^2 or G ~ 1024^3)
* BASE64 -- Base64 encoded string
* ADDR -- IPv4 or IPv6 address
* DNAME -- Domain name
* ... -- Multi-valued item, order of the values is preserved
* [ ] -- Optional value
* | -- Choice
There are 10 main sections (server, control, log, keystore, policy,
key, acl, remote, template, and zone) and module sections with the mod-
prefix. Most of the sections (excluding server and control) 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
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
rate-limit: INT
rate-limit-slip: INT
rate-limit-table-size: INT
rate-limit-whitelist: ADDR[/INT] | ADDR-ADDR ...
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 (see 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 (see
RFC 4892). Set empty value to disable.
Default: server version
nsid
A DNS name server identifier (see 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
rate-limit
Rate limiting is based on the token bucket scheme. A rate basically
represents a number of tokens available each second. Each response is
processed and classified (based on several discriminators, e.g. source
netblock, query type, zone name, rcode, etc.). Classified responses are
then hashed and assigned to a bucket containing number of available
tokens, timestamp and metadata. When available tokens are exhausted,
response is dropped or sent as truncated (see rate-limit-slip). Number
of available tokens is recalculated each second.
Default: 0 (disabled)
rate-limit-table-size
Size of the hash table in a number of buckets. The larger the hash
table, the lesser the probability of a hash collision, but at the
expense of additional memory costs. Each bucket is estimated roughly
to 32 bytes. The size should be selected as a reasonably large prime
due to better hash function distribution properties. Hash table is
internally chained and works well up to a fill rate of 90 %, general
rule of thumb is to select a prime near 1.2 * maximum_qps.
Default: 393241
rate-limit-slip
As attacks using DNS/UDP are usually based on a forged source address,
an attacker could deny services to the victim's netblock if all
responses would be completely blocked. The idea behind SLIP mechanism
is to send each Nth response as truncated, thus allowing client to
reconnect via TCP for at least some degree of service. It is worth
noting, that some responses can't be truncated (e.g. SERVFAIL).
* Setting the value to 0 will cause that all rate-limited responses
will be dropped. The outbound bandwidth and packet rate will be
strictly capped by the rate-limit option. All legitimate requestors
affected by the limit will face denial of service and will observe
excessive timeouts. Therefore this setting is not recommended.
* Setting the value to 1 will cause that all rate-limited responses
will be sent as truncated. The amplification factor of the attack
will be reduced, but the outbound data bandwidth won't be lower than
the incoming bandwidth. Also the outbound packet rate will be the
same as without RRL.
* Setting the value to 2 will cause that half of the rate-limited
responses will be dropped, the other half will be sent as truncated.
With this configuration, both outbound bandwidth and packet rate will
be lower than the inbound. On the other hand, the dropped responses
enlarge the time window for possible cache poisoning attack on the
resolver.
* Setting the value to anything larger than 2 will keep on decreasing
the outgoing rate-limited bandwidth, packet rate, and chances to
notify legitimate requestors to reconnect using TCP. These attributes
are inversely proportional to the configured value. Setting the value
high is not advisable.
Default: 1
rate-limit-whitelist
A list of IP addresses, network subnets, or network ranges to exempt
from rate limiting. Empty list means that no incoming connection will
be white-listed.
Default: not set
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
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.
algorithm
A key algorithm.
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 TSIG key is not required.
Default: not set
action
An ordered list of allowed actions. Empty action list is only allowed
if deny is set.
Possible values:
* transfer -- Allow zone transfer
* notify -- Allow incoming notify
* update -- Allow zone updates
Default: not set
deny
Deny if address, key and action match.
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
KEYSTORE SECTION
DNSSEC keystore configuration.
keystore:
- id: STR
backend: pem | pkcs11
config: STR
id
A keystore identifier.
backend
A key storage backend type. A directory with PEM files or a 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.
NOTE:
Example configuration string for PKCS #11:
"pkcs11:token=knot;pin-value=1234 /usr/lib64/pkcs11/libsofthsm2.so"
Default: kasp-db/keys
POLICY SECTION
DNSSEC policy configuration.
policy:
- id: STR
keystore: STR
manual: BOOL
algorithm: dsa | rsasha1 | dsa-nsec3-sha1 | rsasha1-nsec3-sha1 | rsasha256 | rsasha512 | ecdsap256sha256 | ecdsap384sha384
ksk-size: SIZE
zsk-size: SIZE
dnskey-ttl: TIME
zsk-lifetime: TIME
propagation-delay: TIME
rrsig-lifetime: TIME
rrsig-refresh: TIME
nsec3: BOOL
nsec3-iterations: INT
nsec3-salt-length: INT
nsec3-salt-lifetime: TIME
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
algorithm
An algorithm of signing keys and issued signatures.
Default: ecdsap256sha256
ksk-size
A length of newly generated KSK keys.
Default: 1024 (dsa*), 2048 (rsa*), 256 (ecdsap256*), 384 (ecdsap384*)
zsk-size
A length of newly generated ZSK keys.
Default: see default for ksk-size
dnskey-ttl
A TTL value for DNSKEY records added into zone apex.
Default: zone SOA TTL
NOTE:
has infuence over ZSK key lifetime
zsk-lifetime
A period between ZSK publication and the next rollover initiation.
Default: 30 days
NOTE:
ZSK key lifetime is also infuenced by propagation-delay and
dnskey-ttl
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 day
NOTE:
has infuence over ZSK key lifetime
rrsig-lifetime
A validity period of newly issued signatures.
Default: 14 days
rrsig-refresh
A period how long before a signature expiration the signature will be
refreshed.
Default: 7 days
nsec3
Specifies if NSEC3 will be used instead of NSEC.
Default: off
nsec3-iterations
A number of additional times the hashing is performed.
Default: 5
nsec3-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
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 ise 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
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
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
journal: STR
master: remote_id ...
ddns-master: remote_id
notify: remote_id ...
acl: acl_id ...
semantic-checks: BOOL
disable-any: BOOL
zonefile-sync: TIME
ixfr-from-differences: BOOL
max-journal-size: SIZE
max-zone-size : SIZE
dnssec-signing: BOOL
dnssec-policy: STR
kasp-db: STR
request-edns-option: INT:[HEXSTR]
serial-policy: increment | unixtime
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 files 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
(beware of special characters which are escaped or encoded in the
\DDD form where DDD is corresponding decimal ASCII code). The zone
name doesn't include the terminating dot (the result for the root
zone is the empty string!).
* %% -- means the % character
Default: storage/%s.zone
journal
A path to the zone journal. Non absolute path is relative to storage.
The same set of formatters as for file is supported.
Default: storage/%s.db
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 file 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:
* An extra record together with CNAME record (except for RRSIG and DS)
* SOA record missing in the zone (RFC 1034)
* DNAME records having records under it (DNAME children) (RFC 2672)
Extra checks:
* Missing NS record at the zone apex
* Missing glue A or AAAA records
* Broken or non-cyclic NSEC(3) chain
* Wrong NSEC(3) type bitmap
* Multiple NSEC records at the same node
* Missing NSEC records at authoritative nodes
* NSEC3 insecure delegation that is not part of Opt-out span
* Wrong original TTL value in NSEC3 records
* Wrong RDATA TTL value in RRSIG record
* Signer name in RRSIG RR not the same as in DNSKEY
* Signed RRSIG
* Wrong key flags or wrong key in RRSIG record (not the same as ZSK)
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 disable automatic
zonefile synchronization, -1 value can be used (manual zone flush is
still possible).
NOTE:
If you are serving large zones with frequent updates where the
immediate sync with a zone file is not desirable, increase the
value.
WARNING:
If the zone file is not up-to-date, the zone should be flushed
before its zone file editation or the SOA record must be untouched
after editation. Otherwise the journal can't be applied.
Default: 0 (immediate)
ixfr-from-differences
If enabled, the server creates zone differences from changes you made
to the zone file upon server reload. This option is relevant only if
the server is a master server for the zone.
NOTE:
This option has no effect with enabled dnssec-signing.
Default: off
max-journal-size
Maximum size of the zone journal file.
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.
NOTE:
Cannot be enabled on a slave zone.
Default: off
dnssec-policy
A reference to DNSSEC signing policy. A special default value can be
used for the default policy settings.
Required
kasp-db
A KASP database path. Non absolute path is relative to storage.
Default: storage/keys
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
NOTE:
If your serial was in other than unix time format, be careful with
the transition to unix time. It may happen that the new serial will
be 'lower' than the old one. If this is the case, the transition
should be done by hand (see RFC 1982).
Default: increment
module
An ordered list of references to query modules in the form of
module_name or module_name/module_id. These modules apply only to the
current zone queries.
Default: not set
LOGGING SECTION
Server can be configured to log to the standard output, standard error
output, syslog (or systemd journal if systemd is enabled) or into an
arbitrary file.
There are 6 logging severity levels:
* critical -- Non-recoverable error resulting in server shutdown
* error -- Recoverable error, action should be taken
* warning -- Warning that might require user action
* notice -- Server notice or hint
* info -- Informational message
* debug -- Debug messages (must be turned on at compile time)
In the case of missing log section, warning or more serious messages
will be logged to both standard error output and syslog. The info and
notice messages will be logged to standard output.
log:
- target: stdout | stderr | syslog | STR
server: critical | error | warning | notice | info | debug
zone: critical | error | warning | notice | info | debug
any: critical | error | warning | notice | info | debug
target
A logging output.
Possible values:
* stdout -- Standard output
* stderr -- Standard error output
* syslog -- Syslog
* file_name -- File
server
Minimum severity level for messages related to general operation of the
server that are logged.
Default: not set
zone
Minimum severity level for messages related to zones that are logged.
Default: not set
any
Minimum severity level for all message types that are logged.
Default: not set
MODULE DNSTAP
The module dnstap allows query and response logging.
For all queries logging, use this module in the default template. For
zone-specific logging, use this module in the proper zone
configuration.
mod-dnstap:
- id: STR
sink: STR
identity: STR
version: STR
log-queries: BOOL
log-responses: BOOL
id
A module identifier.
sink
A sink path, which can be either a file or a UNIX socket when prefixed
with unix:.
Required
identity
A DNS server identity. Set empty value to disable.
Default: FQDN hostname
version
A DNS server version. Set empty value to disable.
Default: server version
log-queries
If enabled, query messages will be logged.
Default: on
log-responses
If enabled, response messages will be logged.
Default: on
MODULE SYNTH-RECORD
This module is able to synthesize either forward or reverse records for
the given prefix and subnet.
mod-synth-record:
- id: STR
type: forward | reverse
prefix: STR
origin: DNAME
ttl: INT
network: ADDR[/INT] | ADDR-ADDR
id
A module identifier.
type
The type of generated records.
Possible values:
* forward -- Forward records
* reverse -- Reverse records
Required
prefix
A record owner prefix.
NOTE:
The value doesn't allow dots, address parts in the synthetic names
are separated with a dash.
Default: empty
origin
A zone origin (only valid for the reverse type).
Required
ttl
Time to live of the generated records.
Default: 3600
network
An IP address, a network subnet, or a network range the query must
match.
Required
MODULE DNSPROXY
The module catches all unsatisfied queries and forwards them to the
indicated server for resolution.
mod-dnsproxy:
- id: STR
remote: remote_id
timeout: INT
catch-nxdomain: BOOL
id
A module identifier.
remote
A reference to a remote server where the queries are forwarded to.
Required
timeout
A remote response timeout in milliseconds.
Default: 500
catch-nxdomain
If enabled, all unsatisfied queries (also applies to local zone
lookups) are forwarded.
Default: off
MODULE ROSEDB
The module provides a mean to override responses for certain queries
before the available zones are searched for the record.
mod-rosedb:
- id: STR
dbdir: STR
id
A module identifier.
dbdir
A path to the directory where the database is stored.
Required
AUTHOR
CZ.NIC Labs <http://www.knot-dns.cz>
COPYRIGHT
Copyright 2010--2016, CZ.NIC, z.s.p.o.
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